/*
 * This file is part of STM32 ADC driver
 *
 * Copyright (C) 2016, STMicroelectronics - All Rights Reserved
 * Author: Fabrice Gasnier <fabrice.gasnier@st.com>.
 *
 * License type: GPLv2
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/iio/iio.h>
#include <linux/iio/buffer.h>
#include <linux/iio/timer/stm32-timer-trigger.h>
#include <linux/iio/trigger.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_device.h>

#include "stm32-adc-core.h"

/* STM32F4 - Registers for each ADC instance */
#define STM32F4_ADC_SR                  0x00
#define STM32F4_ADC_CR1                 0x04
#define STM32F4_ADC_CR2                 0x08
#define STM32F4_ADC_SMPR1               0x0C
#define STM32F4_ADC_SMPR2               0x10
#define STM32F4_ADC_HTR                 0x24
#define STM32F4_ADC_LTR                 0x28
#define STM32F4_ADC_SQR1                0x2C
#define STM32F4_ADC_SQR2                0x30
#define STM32F4_ADC_SQR3                0x34
#define STM32F4_ADC_JSQR                0x38
#define STM32F4_ADC_JDR1                0x3C
#define STM32F4_ADC_JDR2                0x40
#define STM32F4_ADC_JDR3                0x44
#define STM32F4_ADC_JDR4                0x48
#define STM32F4_ADC_DR                  0x4C

/* STM32F4_ADC_SR - bit fields */
#define STM32F4_STRT                    BIT(4)
#define STM32F4_EOC                     BIT(1)

/* STM32F4_ADC_CR1 - bit fields */
#define STM32F4_RES_SHIFT               24
#define STM32F4_RES_MASK                GENMASK(25, 24)
#define STM32F4_SCAN                    BIT(8)
#define STM32F4_EOCIE                   BIT(5)

/* STM32F4_ADC_CR2 - bit fields */
#define STM32F4_SWSTART                 BIT(30)
#define STM32F4_EXTEN_SHIFT             28
#define STM32F4_EXTEN_MASK              GENMASK(29, 28)
#define STM32F4_EXTSEL_SHIFT            24
#define STM32F4_EXTSEL_MASK             GENMASK(27, 24)
#define STM32F4_EOCS                    BIT(10)
#define STM32F4_DDS                     BIT(9)
#define STM32F4_DMA                     BIT(8)
#define STM32F4_ADON                    BIT(0)

/* STM32H7 - Registers for each ADC instance */
#define STM32H7_ADC_ISR                 0x00
#define STM32H7_ADC_IER                 0x04
#define STM32H7_ADC_CR                  0x08
#define STM32H7_ADC_CFGR                0x0C
#define STM32H7_ADC_PCSEL               0x1C
#define STM32H7_ADC_SQR1                0x30
#define STM32H7_ADC_SQR2                0x34
#define STM32H7_ADC_SQR3                0x38
#define STM32H7_ADC_SQR4                0x3C
#define STM32H7_ADC_DR                  0x40
#define STM32H7_ADC_CALFACT             0xC4
#define STM32H7_ADC_CALFACT2            0xC8

/* STM32H7_ADC_ISR - bit fields */
#define STM32H7_EOC                     BIT(2)
#define STM32H7_ADRDY                   BIT(0)

/* STM32H7_ADC_IER - bit fields */
#define STM32H7_EOCIE                   STM32H7_EOC

/* STM32H7_ADC_CR - bit fields */
#define STM32H7_ADCAL                   BIT(31)
#define STM32H7_ADCALDIF                BIT(30)
#define STM32H7_DEEPPWD                 BIT(29)
#define STM32H7_ADVREGEN                BIT(28)
#define STM32H7_LINCALRDYW6             BIT(27)
#define STM32H7_LINCALRDYW5             BIT(26)
#define STM32H7_LINCALRDYW4             BIT(25)
#define STM32H7_LINCALRDYW3             BIT(24)
#define STM32H7_LINCALRDYW2             BIT(23)
#define STM32H7_LINCALRDYW1             BIT(22)
#define STM32H7_ADCALLIN                BIT(16)
#define STM32H7_BOOST                   BIT(8)
#define STM32H7_ADSTP                   BIT(4)
#define STM32H7_ADSTART                 BIT(2)
#define STM32H7_ADDIS                   BIT(1)
#define STM32H7_ADEN                    BIT(0)

/* STM32H7_ADC_CFGR bit fields */
#define STM32H7_EXTEN_SHIFT             10
#define STM32H7_EXTEN_MASK              GENMASK(11, 10)
#define STM32H7_EXTSEL_SHIFT            5
#define STM32H7_EXTSEL_MASK             GENMASK(9, 5)
#define STM32H7_RES_SHIFT               2
#define STM32H7_RES_MASK                GENMASK(4, 2)
#define STM32H7_DMNGT_SHIFT             0
#define STM32H7_DMNGT_MASK              GENMASK(1, 0)

enum stm32h7_adc_dmngt {
        STM32H7_DMNGT_DR_ONLY,          /* Regular data in DR only */
        STM32H7_DMNGT_DMA_ONESHOT,      /* DMA one shot mode */
        STM32H7_DMNGT_DFSDM,            /* DFSDM mode */
        STM32H7_DMNGT_DMA_CIRC,         /* DMA circular mode */
};

/* STM32H7_ADC_CALFACT - bit fields */
#define STM32H7_CALFACT_D_SHIFT         16
#define STM32H7_CALFACT_D_MASK          GENMASK(26, 16)
#define STM32H7_CALFACT_S_SHIFT         0
#define STM32H7_CALFACT_S_MASK          GENMASK(10, 0)

/* STM32H7_ADC_CALFACT2 - bit fields */
#define STM32H7_LINCALFACT_SHIFT        0
#define STM32H7_LINCALFACT_MASK         GENMASK(29, 0)

/* Number of linear calibration shadow registers / LINCALRDYW control bits */
#define STM32H7_LINCALFACT_NUM          6

/* BOOST bit must be set on STM32H7 when ADC clock is above 20MHz */
#define STM32H7_BOOST_CLKRATE           20000000UL

#define STM32_ADC_MAX_SQ                16      /* SQ1..SQ16 */
#define STM32_ADC_TIMEOUT_US            100000
#define STM32_ADC_TIMEOUT       (msecs_to_jiffies(STM32_ADC_TIMEOUT_US / 1000))

#define STM32_DMA_BUFFER_SIZE           PAGE_SIZE

/* External trigger enable */
enum stm32_adc_exten {
        STM32_EXTEN_SWTRIG,
        STM32_EXTEN_HWTRIG_RISING_EDGE,
        STM32_EXTEN_HWTRIG_FALLING_EDGE,
        STM32_EXTEN_HWTRIG_BOTH_EDGES,
};

/* extsel - trigger mux selection value */
enum stm32_adc_extsel {
        STM32_EXT0,
        STM32_EXT1,
        STM32_EXT2,
        STM32_EXT3,
        STM32_EXT4,
        STM32_EXT5,
        STM32_EXT6,
        STM32_EXT7,
        STM32_EXT8,
        STM32_EXT9,
        STM32_EXT10,
        STM32_EXT11,
        STM32_EXT12,
        STM32_EXT13,
        STM32_EXT14,
        STM32_EXT15,
};

/**
 * struct stm32_adc_trig_info - ADC trigger info
 * @name:               name of the trigger, corresponding to its source
 * @extsel:             trigger selection
 */
struct stm32_adc_trig_info {
        const char *name;
        enum stm32_adc_extsel extsel;
};

/**
 * struct stm32_adc_calib - optional adc calibration data
 * @calfact_s: Calibration offset for single ended channels
 * @calfact_d: Calibration offset in differential
 * @lincalfact: Linearity calibration factor
 */
struct stm32_adc_calib {
        u32                     calfact_s;
        u32                     calfact_d;
        u32                     lincalfact[STM32H7_LINCALFACT_NUM];
};

/**
 * stm32_adc_regs - stm32 ADC misc registers & bitfield desc
 * @reg:                register offset
 * @mask:               bitfield mask
 * @shift:              left shift
 */
struct stm32_adc_regs {
        int reg;
        int mask;
        int shift;
};

/**
 * stm32_adc_regspec - stm32 registers definition, compatible dependent data
 * @dr:                 data register offset
 * @ier_eoc:            interrupt enable register & eocie bitfield
 * @isr_eoc:            interrupt status register & eoc bitfield
 * @sqr:                reference to sequence registers array
 * @exten:              trigger control register & bitfield
 * @extsel:             trigger selection register & bitfield
 * @res:                resolution selection register & bitfield
 */
struct stm32_adc_regspec {
        const u32 dr;
        const struct stm32_adc_regs ier_eoc;
        const struct stm32_adc_regs isr_eoc;
        const struct stm32_adc_regs *sqr;
        const struct stm32_adc_regs exten;
        const struct stm32_adc_regs extsel;
        const struct stm32_adc_regs res;
};

struct stm32_adc;

/**
 * stm32_adc_cfg - stm32 compatible configuration data
 * @regs:               registers descriptions
 * @adc_info:           per instance input channels definitions
 * @trigs:              external trigger sources
 * @clk_required:       clock is required
 * @selfcalib:          optional routine for self-calibration
 * @prepare:            optional prepare routine (power-up, enable)
 * @start_conv:         routine to start conversions
 * @stop_conv:          routine to stop conversions
 * @unprepare:          optional unprepare routine (disable, power-down)
 */
struct stm32_adc_cfg {
        const struct stm32_adc_regspec  *regs;
        const struct stm32_adc_info     *adc_info;
        struct stm32_adc_trig_info      *trigs;
        bool clk_required;
        int (*selfcalib)(struct stm32_adc *);
        int (*prepare)(struct stm32_adc *);
        void (*start_conv)(struct stm32_adc *, bool dma);
        void (*stop_conv)(struct stm32_adc *);
        void (*unprepare)(struct stm32_adc *);
};

/**
 * struct stm32_adc - private data of each ADC IIO instance
 * @common:             reference to ADC block common data
 * @offset:             ADC instance register offset in ADC block
 * @cfg:                compatible configuration data
 * @completion:         end of single conversion completion
 * @buffer:             data buffer
 * @clk:                clock for this adc instance
 * @irq:                interrupt for this adc instance
 * @lock:               spinlock
 * @bufi:               data buffer index
 * @num_conv:           expected number of scan conversions
 * @res:                data resolution (e.g. RES bitfield value)
 * @trigger_polarity:   external trigger polarity (e.g. exten)
 * @dma_chan:           dma channel
 * @rx_buf:             dma rx buffer cpu address
 * @rx_dma_buf:         dma rx buffer bus address
 * @rx_buf_sz:          dma rx buffer size
 * @pcsel               bitmask to preselect channels on some devices
 * @cal:                optional calibration data on some devices
 */
struct stm32_adc {
        struct stm32_adc_common *common;
        u32                     offset;
        const struct stm32_adc_cfg      *cfg;
        struct completion       completion;
        u16                     buffer[STM32_ADC_MAX_SQ];
        struct clk              *clk;
        int                     irq;
        spinlock_t              lock;           /* interrupt lock */
        unsigned int            bufi;
        unsigned int            num_conv;
        u32                     res;
        u32                     trigger_polarity;
        struct dma_chan         *dma_chan;
        u8                      *rx_buf;
        dma_addr_t              rx_dma_buf;
        unsigned int            rx_buf_sz;
        u32                     pcsel;
        struct stm32_adc_calib  cal;
};

/**
 * struct stm32_adc_chan_spec - specification of stm32 adc channel
 * @type:       IIO channel type
 * @channel:    channel number (single ended)
 * @name:       channel name (single ended)
 */
struct stm32_adc_chan_spec {
        enum iio_chan_type      type;
        int                     channel;
        const char              *name;
};

/**
 * struct stm32_adc_info - stm32 ADC, per instance config data
 * @channels:           Reference to stm32 channels spec
 * @max_channels:       Number of channels
 * @resolutions:        available resolutions
 * @num_res:            number of available resolutions
 */
struct stm32_adc_info {
        const struct stm32_adc_chan_spec *channels;
        int max_channels;
        const unsigned int *resolutions;
        const unsigned int num_res;
};

/*
 * Input definitions common for all instances:
 * stm32f4 can have up to 16 channels
 * stm32h7 can have up to 20 channels
 */
static const struct stm32_adc_chan_spec stm32_adc_channels[] = {
        { IIO_VOLTAGE, 0, "in0" },
        { IIO_VOLTAGE, 1, "in1" },
        { IIO_VOLTAGE, 2, "in2" },
        { IIO_VOLTAGE, 3, "in3" },
        { IIO_VOLTAGE, 4, "in4" },
        { IIO_VOLTAGE, 5, "in5" },
        { IIO_VOLTAGE, 6, "in6" },
        { IIO_VOLTAGE, 7, "in7" },
        { IIO_VOLTAGE, 8, "in8" },
        { IIO_VOLTAGE, 9, "in9" },
        { IIO_VOLTAGE, 10, "in10" },
        { IIO_VOLTAGE, 11, "in11" },
        { IIO_VOLTAGE, 12, "in12" },
        { IIO_VOLTAGE, 13, "in13" },
        { IIO_VOLTAGE, 14, "in14" },
        { IIO_VOLTAGE, 15, "in15" },
        { IIO_VOLTAGE, 16, "in16" },
        { IIO_VOLTAGE, 17, "in17" },
        { IIO_VOLTAGE, 18, "in18" },
        { IIO_VOLTAGE, 19, "in19" },
};

static const unsigned int stm32f4_adc_resolutions[] = {
        /* sorted values so the index matches RES[1:0] in STM32F4_ADC_CR1 */
        12, 10, 8, 6,
};

static const struct stm32_adc_info stm32f4_adc_info = {
        .channels = stm32_adc_channels,
        .max_channels = 16,
        .resolutions = stm32f4_adc_resolutions,
        .num_res = ARRAY_SIZE(stm32f4_adc_resolutions),
};

static const unsigned int stm32h7_adc_resolutions[] = {
        /* sorted values so the index matches RES[2:0] in STM32H7_ADC_CFGR */
        16, 14, 12, 10, 8,
};

static const struct stm32_adc_info stm32h7_adc_info = {
        .channels = stm32_adc_channels,
        .max_channels = 20,
        .resolutions = stm32h7_adc_resolutions,
        .num_res = ARRAY_SIZE(stm32h7_adc_resolutions),
};

/**
 * stm32f4_sq - describe regular sequence registers
 * - L: sequence len (register & bit field)
 * - SQ1..SQ16: sequence entries (register & bit field)
 */
static const struct stm32_adc_regs stm32f4_sq[STM32_ADC_MAX_SQ + 1] = {
        /* L: len bit field description to be kept as first element */
        { STM32F4_ADC_SQR1, GENMASK(23, 20), 20 },
        /* SQ1..SQ16 registers & bit fields (reg, mask, shift) */
        { STM32F4_ADC_SQR3, GENMASK(4, 0), 0 },
        { STM32F4_ADC_SQR3, GENMASK(9, 5), 5 },
        { STM32F4_ADC_SQR3, GENMASK(14, 10), 10 },
        { STM32F4_ADC_SQR3, GENMASK(19, 15), 15 },
        { STM32F4_ADC_SQR3, GENMASK(24, 20), 20 },
        { STM32F4_ADC_SQR3, GENMASK(29, 25), 25 },
        { STM32F4_ADC_SQR2, GENMASK(4, 0), 0 },
        { STM32F4_ADC_SQR2, GENMASK(9, 5), 5 },
        { STM32F4_ADC_SQR2, GENMASK(14, 10), 10 },
        { STM32F4_ADC_SQR2, GENMASK(19, 15), 15 },
        { STM32F4_ADC_SQR2, GENMASK(24, 20), 20 },
        { STM32F4_ADC_SQR2, GENMASK(29, 25), 25 },
        { STM32F4_ADC_SQR1, GENMASK(4, 0), 0 },
        { STM32F4_ADC_SQR1, GENMASK(9, 5), 5 },
        { STM32F4_ADC_SQR1, GENMASK(14, 10), 10 },
        { STM32F4_ADC_SQR1, GENMASK(19, 15), 15 },
};

/* STM32F4 external trigger sources for all instances */
static struct stm32_adc_trig_info stm32f4_adc_trigs[] = {
        { TIM1_CH1, STM32_EXT0 },
        { TIM1_CH2, STM32_EXT1 },
        { TIM1_CH3, STM32_EXT2 },
        { TIM2_CH2, STM32_EXT3 },
        { TIM2_CH3, STM32_EXT4 },
        { TIM2_CH4, STM32_EXT5 },
        { TIM2_TRGO, STM32_EXT6 },
        { TIM3_CH1, STM32_EXT7 },
        { TIM3_TRGO, STM32_EXT8 },
        { TIM4_CH4, STM32_EXT9 },
        { TIM5_CH1, STM32_EXT10 },
        { TIM5_CH2, STM32_EXT11 },
        { TIM5_CH3, STM32_EXT12 },
        { TIM8_CH1, STM32_EXT13 },
        { TIM8_TRGO, STM32_EXT14 },
        {}, /* sentinel */
};

static const struct stm32_adc_regspec stm32f4_adc_regspec = {
        .dr = STM32F4_ADC_DR,
        .ier_eoc = { STM32F4_ADC_CR1, STM32F4_EOCIE },
        .isr_eoc = { STM32F4_ADC_SR, STM32F4_EOC },
        .sqr = stm32f4_sq,
        .exten = { STM32F4_ADC_CR2, STM32F4_EXTEN_MASK, STM32F4_EXTEN_SHIFT },
        .extsel = { STM32F4_ADC_CR2, STM32F4_EXTSEL_MASK,
                    STM32F4_EXTSEL_SHIFT },
        .res = { STM32F4_ADC_CR1, STM32F4_RES_MASK, STM32F4_RES_SHIFT },
};

static const struct stm32_adc_regs stm32h7_sq[STM32_ADC_MAX_SQ + 1] = {
        /* L: len bit field description to be kept as first element */
        { STM32H7_ADC_SQR1, GENMASK(3, 0), 0 },
        /* SQ1..SQ16 registers & bit fields (reg, mask, shift) */
        { STM32H7_ADC_SQR1, GENMASK(10, 6), 6 },
        { STM32H7_ADC_SQR1, GENMASK(16, 12), 12 },
        { STM32H7_ADC_SQR1, GENMASK(22, 18), 18 },
        { STM32H7_ADC_SQR1, GENMASK(28, 24), 24 },
        { STM32H7_ADC_SQR2, GENMASK(4, 0), 0 },
        { STM32H7_ADC_SQR2, GENMASK(10, 6), 6 },
        { STM32H7_ADC_SQR2, GENMASK(16, 12), 12 },
        { STM32H7_ADC_SQR2, GENMASK(22, 18), 18 },
        { STM32H7_ADC_SQR2, GENMASK(28, 24), 24 },
        { STM32H7_ADC_SQR3, GENMASK(4, 0), 0 },
        { STM32H7_ADC_SQR3, GENMASK(10, 6), 6 },
        { STM32H7_ADC_SQR3, GENMASK(16, 12), 12 },
        { STM32H7_ADC_SQR3, GENMASK(22, 18), 18 },
        { STM32H7_ADC_SQR3, GENMASK(28, 24), 24 },
        { STM32H7_ADC_SQR4, GENMASK(4, 0), 0 },
        { STM32H7_ADC_SQR4, GENMASK(10, 6), 6 },
};

/* STM32H7 external trigger sources for all instances */
static struct stm32_adc_trig_info stm32h7_adc_trigs[] = {
        { TIM1_CH1, STM32_EXT0 },
        { TIM1_CH2, STM32_EXT1 },
        { TIM1_CH3, STM32_EXT2 },
        { TIM2_CH2, STM32_EXT3 },
        { TIM3_TRGO, STM32_EXT4 },
        { TIM4_CH4, STM32_EXT5 },
        { TIM8_TRGO, STM32_EXT7 },
        { TIM8_TRGO2, STM32_EXT8 },
        { TIM1_TRGO, STM32_EXT9 },
        { TIM1_TRGO2, STM32_EXT10 },
        { TIM2_TRGO, STM32_EXT11 },
        { TIM4_TRGO, STM32_EXT12 },
        { TIM6_TRGO, STM32_EXT13 },
        { TIM3_CH4, STM32_EXT15 },
        {},
};

static const struct stm32_adc_regspec stm32h7_adc_regspec = {
        .dr = STM32H7_ADC_DR,
        .ier_eoc = { STM32H7_ADC_IER, STM32H7_EOCIE },
        .isr_eoc = { STM32H7_ADC_ISR, STM32H7_EOC },
        .sqr = stm32h7_sq,
        .exten = { STM32H7_ADC_CFGR, STM32H7_EXTEN_MASK, STM32H7_EXTEN_SHIFT },
        .extsel = { STM32H7_ADC_CFGR, STM32H7_EXTSEL_MASK,
                    STM32H7_EXTSEL_SHIFT },
        .res = { STM32H7_ADC_CFGR, STM32H7_RES_MASK, STM32H7_RES_SHIFT },
};

/**
 * STM32 ADC registers access routines
 * @adc: stm32 adc instance
 * @reg: reg offset in adc instance
 *
 * Note: All instances share same base, with 0x0, 0x100 or 0x200 offset resp.
 * for adc1, adc2 and adc3.
 */
static u32 stm32_adc_readl(struct stm32_adc *adc, u32 reg)
{
        return readl_relaxed(adc->common->base + adc->offset + reg);
}

#define stm32_adc_readl_addr(addr)      stm32_adc_readl(adc, addr)

#define stm32_adc_readl_poll_timeout(reg, val, cond, sleep_us, timeout_us) \
        readx_poll_timeout(stm32_adc_readl_addr, reg, val, \
                           cond, sleep_us, timeout_us)

static u16 stm32_adc_readw(struct stm32_adc *adc, u32 reg)
{
        return readw_relaxed(adc->common->base + adc->offset + reg);
}

static void stm32_adc_writel(struct stm32_adc *adc, u32 reg, u32 val)
{
        writel_relaxed(val, adc->common->base + adc->offset + reg);
}

static void stm32_adc_set_bits(struct stm32_adc *adc, u32 reg, u32 bits)
{
        unsigned long flags;

        spin_lock_irqsave(&adc->lock, flags);
        stm32_adc_writel(adc, reg, stm32_adc_readl(adc, reg) | bits);
        spin_unlock_irqrestore(&adc->lock, flags);
}

static void stm32_adc_clr_bits(struct stm32_adc *adc, u32 reg, u32 bits)
{
        unsigned long flags;

        spin_lock_irqsave(&adc->lock, flags);
        stm32_adc_writel(adc, reg, stm32_adc_readl(adc, reg) & ~bits);
        spin_unlock_irqrestore(&adc->lock, flags);
}

/**
 * stm32_adc_conv_irq_enable() - Enable end of conversion interrupt
 * @adc: stm32 adc instance
 */
static void stm32_adc_conv_irq_enable(struct stm32_adc *adc)
{
        stm32_adc_set_bits(adc, adc->cfg->regs->ier_eoc.reg,
                           adc->cfg->regs->ier_eoc.mask);
};

/**
 * stm32_adc_conv_irq_disable() - Disable end of conversion interrupt
 * @adc: stm32 adc instance
 */
static void stm32_adc_conv_irq_disable(struct stm32_adc *adc)
{
        stm32_adc_clr_bits(adc, adc->cfg->regs->ier_eoc.reg,
                           adc->cfg->regs->ier_eoc.mask);
}

static void stm32_adc_set_res(struct stm32_adc *adc)
{
        const struct stm32_adc_regs *res = &adc->cfg->regs->res;
        u32 val;

        val = stm32_adc_readl(adc, res->reg);
        val = (val & ~res->mask) | (adc->res << res->shift);
        stm32_adc_writel(adc, res->reg, val);
}

/**
 * stm32f4_adc_start_conv() - Start conversions for regular channels.
 * @adc: stm32 adc instance
 * @dma: use dma to transfer conversion result
 *
 * Start conversions for regular channels.
 * Also take care of normal or DMA mode. Circular DMA may be used for regular
 * conversions, in IIO buffer modes. Otherwise, use ADC interrupt with direct
 * DR read instead (e.g. read_raw, or triggered buffer mode without DMA).
 */
static void stm32f4_adc_start_conv(struct stm32_adc *adc, bool dma)
{
        stm32_adc_set_bits(adc, STM32F4_ADC_CR1, STM32F4_SCAN);

        if (dma)
                stm32_adc_set_bits(adc, STM32F4_ADC_CR2,
                                   STM32F4_DMA | STM32F4_DDS);

        stm32_adc_set_bits(adc, STM32F4_ADC_CR2, STM32F4_EOCS | STM32F4_ADON);

        /* Wait for Power-up time (tSTAB from datasheet) */
        usleep_range(2, 3);

        /* Software start ? (e.g. trigger detection disabled ?) */
        if (!(stm32_adc_readl(adc, STM32F4_ADC_CR2) & STM32F4_EXTEN_MASK))
                stm32_adc_set_bits(adc, STM32F4_ADC_CR2, STM32F4_SWSTART);
}

static void stm32f4_adc_stop_conv(struct stm32_adc *adc)
{
        stm32_adc_clr_bits(adc, STM32F4_ADC_CR2, STM32F4_EXTEN_MASK);
        stm32_adc_clr_bits(adc, STM32F4_ADC_SR, STM32F4_STRT);

        stm32_adc_clr_bits(adc, STM32F4_ADC_CR1, STM32F4_SCAN);
        stm32_adc_clr_bits(adc, STM32F4_ADC_CR2,
                           STM32F4_ADON | STM32F4_DMA | STM32F4_DDS);
}

static void stm32h7_adc_start_conv(struct stm32_adc *adc, bool dma)
{
        enum stm32h7_adc_dmngt dmngt;
        unsigned long flags;
        u32 val;

        if (dma)
                dmngt = STM32H7_DMNGT_DMA_CIRC;
        else
                dmngt = STM32H7_DMNGT_DR_ONLY;

        spin_lock_irqsave(&adc->lock, flags);
        val = stm32_adc_readl(adc, STM32H7_ADC_CFGR);
        val = (val & ~STM32H7_DMNGT_MASK) | (dmngt << STM32H7_DMNGT_SHIFT);
        stm32_adc_writel(adc, STM32H7_ADC_CFGR, val);
        spin_unlock_irqrestore(&adc->lock, flags);

        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADSTART);
}

static void stm32h7_adc_stop_conv(struct stm32_adc *adc)
{
        struct iio_dev *indio_dev = iio_priv_to_dev(adc);
        int ret;
        u32 val;

        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADSTP);

        ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
                                           !(val & (STM32H7_ADSTART)),
                                           100, STM32_ADC_TIMEOUT_US);
        if (ret)
                dev_warn(&indio_dev->dev, "stop failed\n");

        stm32_adc_clr_bits(adc, STM32H7_ADC_CFGR, STM32H7_DMNGT_MASK);
}

static void stm32h7_adc_exit_pwr_down(struct stm32_adc *adc)
{
        /* Exit deep power down, then enable ADC voltage regulator */
        stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_DEEPPWD);
        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADVREGEN);

        if (adc->common->rate > STM32H7_BOOST_CLKRATE)
                stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_BOOST);

        /* Wait for startup time */
        usleep_range(10, 20);
}

static void stm32h7_adc_enter_pwr_down(struct stm32_adc *adc)
{
        stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_BOOST);

        /* Setting DEEPPWD disables ADC vreg and clears ADVREGEN */
        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_DEEPPWD);
}

static int stm32h7_adc_enable(struct stm32_adc *adc)
{
        struct iio_dev *indio_dev = iio_priv_to_dev(adc);
        int ret;
        u32 val;

        /* Clear ADRDY by writing one, then enable ADC */
        stm32_adc_set_bits(adc, STM32H7_ADC_ISR, STM32H7_ADRDY);
        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADEN);

        /* Poll for ADRDY to be set (after adc startup time) */
        ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_ISR, val,
                                           val & STM32H7_ADRDY,
                                           100, STM32_ADC_TIMEOUT_US);
        if (ret) {
                stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_ADEN);
                dev_err(&indio_dev->dev, "Failed to enable ADC\n");
        }

        return ret;
}

static void stm32h7_adc_disable(struct stm32_adc *adc)
{
        struct iio_dev *indio_dev = iio_priv_to_dev(adc);
        int ret;
        u32 val;

        /* Disable ADC and wait until it's effectively disabled */
        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADDIS);
        ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
                                           !(val & STM32H7_ADEN), 100,
                                           STM32_ADC_TIMEOUT_US);
        if (ret)
                dev_warn(&indio_dev->dev, "Failed to disable\n");
}

/**
 * stm32h7_adc_read_selfcalib() - read calibration shadow regs, save result
 * @adc: stm32 adc instance
 */
static int stm32h7_adc_read_selfcalib(struct stm32_adc *adc)
{
        struct iio_dev *indio_dev = iio_priv_to_dev(adc);
        int i, ret;
        u32 lincalrdyw_mask, val;

        /* Enable adc so LINCALRDYW1..6 bits are writable */
        ret = stm32h7_adc_enable(adc);
        if (ret)
                return ret;

        /* Read linearity calibration */
        lincalrdyw_mask = STM32H7_LINCALRDYW6;
        for (i = STM32H7_LINCALFACT_NUM - 1; i >= 0; i--) {
                /* Clear STM32H7_LINCALRDYW[6..1]: transfer calib to CALFACT2 */
                stm32_adc_clr_bits(adc, STM32H7_ADC_CR, lincalrdyw_mask);

                /* Poll: wait calib data to be ready in CALFACT2 register */
                ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
                                                   !(val & lincalrdyw_mask),
                                                   100, STM32_ADC_TIMEOUT_US);
                if (ret) {
                        dev_err(&indio_dev->dev, "Failed to read calfact\n");
                        goto disable;
                }

                val = stm32_adc_readl(adc, STM32H7_ADC_CALFACT2);
                adc->cal.lincalfact[i] = (val & STM32H7_LINCALFACT_MASK);
                adc->cal.lincalfact[i] >>= STM32H7_LINCALFACT_SHIFT;

                lincalrdyw_mask >>= 1;
        }

        /* Read offset calibration */
        val = stm32_adc_readl(adc, STM32H7_ADC_CALFACT);
        adc->cal.calfact_s = (val & STM32H7_CALFACT_S_MASK);
        adc->cal.calfact_s >>= STM32H7_CALFACT_S_SHIFT;
        adc->cal.calfact_d = (val & STM32H7_CALFACT_D_MASK);
        adc->cal.calfact_d >>= STM32H7_CALFACT_D_SHIFT;

disable:
        stm32h7_adc_disable(adc);

        return ret;
}

/**
 * stm32h7_adc_restore_selfcalib() - Restore saved self-calibration result
 * @adc: stm32 adc instance
 * Note: ADC must be enabled, with no on-going conversions.
 */
static int stm32h7_adc_restore_selfcalib(struct stm32_adc *adc)
{
        struct iio_dev *indio_dev = iio_priv_to_dev(adc);
        int i, ret;
        u32 lincalrdyw_mask, val;

        val = (adc->cal.calfact_s << STM32H7_CALFACT_S_SHIFT) |
                (adc->cal.calfact_d << STM32H7_CALFACT_D_SHIFT);
        stm32_adc_writel(adc, STM32H7_ADC_CALFACT, val);

        lincalrdyw_mask = STM32H7_LINCALRDYW6;
        for (i = STM32H7_LINCALFACT_NUM - 1; i >= 0; i--) {
                /*
                 * Write saved calibration data to shadow registers:
                 * Write CALFACT2, and set LINCALRDYW[6..1] bit to trigger
                 * data write. Then poll to wait for complete transfer.
                 */
                val = adc->cal.lincalfact[i] << STM32H7_LINCALFACT_SHIFT;
                stm32_adc_writel(adc, STM32H7_ADC_CALFACT2, val);
                stm32_adc_set_bits(adc, STM32H7_ADC_CR, lincalrdyw_mask);
                ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
                                                   val & lincalrdyw_mask,
                                                   100, STM32_ADC_TIMEOUT_US);
                if (ret) {
                        dev_err(&indio_dev->dev, "Failed to write calfact\n");
                        return ret;
                }

                /*
                 * Read back calibration data, has two effects:
                 * - It ensures bits LINCALRDYW[6..1] are kept cleared
                 *   for next time calibration needs to be restored.
                 * - BTW, bit clear triggers a read, then check data has been
                 *   correctly written.
                 */
                stm32_adc_clr_bits(adc, STM32H7_ADC_CR, lincalrdyw_mask);
                ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
                                                   !(val & lincalrdyw_mask),
                                                   100, STM32_ADC_TIMEOUT_US);
                if (ret) {
                        dev_err(&indio_dev->dev, "Failed to read calfact\n");
                        return ret;
                }
                val = stm32_adc_readl(adc, STM32H7_ADC_CALFACT2);
                if (val != adc->cal.lincalfact[i] << STM32H7_LINCALFACT_SHIFT) {
                        dev_err(&indio_dev->dev, "calfact not consistent\n");
                        return -EIO;
                }

                lincalrdyw_mask >>= 1;
        }

        return 0;
}

/**
 * Fixed timeout value for ADC calibration.
 * worst cases:
 * - low clock frequency
 * - maximum prescalers
 * Calibration requires:
 * - 131,072 ADC clock cycle for the linear calibration
 * - 20 ADC clock cycle for the offset calibration
 *
 * Set to 100ms for now
 */
#define STM32H7_ADC_CALIB_TIMEOUT_US            100000

/**
 * stm32h7_adc_selfcalib() - Procedure to calibrate ADC (from power down)
 * @adc: stm32 adc instance
 * Exit from power down, calibrate ADC, then return to power down.
 */
static int stm32h7_adc_selfcalib(struct stm32_adc *adc)
{
        struct iio_dev *indio_dev = iio_priv_to_dev(adc);
        int ret;
        u32 val;

        stm32h7_adc_exit_pwr_down(adc);

        /*
         * Select calibration mode:
         * - Offset calibration for single ended inputs
         * - No linearity calibration (do it later, before reading it)
         */
        stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_ADCALDIF);
        stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_ADCALLIN);

        /* Start calibration, then wait for completion */
        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADCAL);
        ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
                                           !(val & STM32H7_ADCAL), 100,
                                           STM32H7_ADC_CALIB_TIMEOUT_US);
        if (ret) {
                dev_err(&indio_dev->dev, "calibration failed\n");
                goto pwr_dwn;
        }

        /*
         * Select calibration mode, then start calibration:
         * - Offset calibration for differential input
         * - Linearity calibration (needs to be done only once for single/diff)
         *   will run simultaneously with offset calibration.
         */
        stm32_adc_set_bits(adc, STM32H7_ADC_CR,
                           STM32H7_ADCALDIF | STM32H7_ADCALLIN);
        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADCAL);
        ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
                                           !(val & STM32H7_ADCAL), 100,
                                           STM32H7_ADC_CALIB_TIMEOUT_US);
        if (ret) {
                dev_err(&indio_dev->dev, "calibration failed\n");
                goto pwr_dwn;
        }

        stm32_adc_clr_bits(adc, STM32H7_ADC_CR,
                           STM32H7_ADCALDIF | STM32H7_ADCALLIN);

        /* Read calibration result for future reference */
        ret = stm32h7_adc_read_selfcalib(adc);

pwr_dwn:
        stm32h7_adc_enter_pwr_down(adc);

        return ret;
}

/**
 * stm32h7_adc_prepare() - Leave power down mode to enable ADC.
 * @adc: stm32 adc instance
 * Leave power down mode.
 * Enable ADC.
 * Restore calibration data.
 * Pre-select channels that may be used in PCSEL (required by input MUX / IO).
 */
static int stm32h7_adc_prepare(struct stm32_adc *adc)
{
        int ret;

        stm32h7_adc_exit_pwr_down(adc);

        ret = stm32h7_adc_enable(adc);
        if (ret)
                goto pwr_dwn;

        ret = stm32h7_adc_restore_selfcalib(adc);
        if (ret)
                goto disable;

        stm32_adc_writel(adc, STM32H7_ADC_PCSEL, adc->pcsel);

        return 0;

disable:
        stm32h7_adc_disable(adc);
pwr_dwn:
        stm32h7_adc_enter_pwr_down(adc);

        return ret;
}

static void stm32h7_adc_unprepare(struct stm32_adc *adc)
{
        stm32h7_adc_disable(adc);
        stm32h7_adc_enter_pwr_down(adc);
}

/**
 * stm32_adc_conf_scan_seq() - Build regular channels scan sequence
 * @indio_dev: IIO device
 * @scan_mask: channels to be converted
 *
 * Conversion sequence :
 * Configure ADC scan sequence based on selected channels in scan_mask.
 * Add channels to SQR registers, from scan_mask LSB to MSB, then
 * program sequence len.
 */
static int stm32_adc_conf_scan_seq(struct iio_dev *indio_dev,
                                   const unsigned long *scan_mask)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        const struct stm32_adc_regs *sqr = adc->cfg->regs->sqr;
        const struct iio_chan_spec *chan;
        u32 val, bit;
        int i = 0;

        for_each_set_bit(bit, scan_mask, indio_dev->masklength) {
                chan = indio_dev->channels + bit;
                /*
                 * Assign one channel per SQ entry in regular
                 * sequence, starting with SQ1.
                 */
                i++;
                if (i > STM32_ADC_MAX_SQ)
                        return -EINVAL;

                dev_dbg(&indio_dev->dev, "%s chan %d to SQ%d\n",
                        __func__, chan->channel, i);

                val = stm32_adc_readl(adc, sqr[i].reg);
                val &= ~sqr[i].mask;
                val |= chan->channel << sqr[i].shift;
                stm32_adc_writel(adc, sqr[i].reg, val);
        }

        if (!i)
                return -EINVAL;

        /* Sequence len */
        val = stm32_adc_readl(adc, sqr[0].reg);
        val &= ~sqr[0].mask;
        val |= ((i - 1) << sqr[0].shift);
        stm32_adc_writel(adc, sqr[0].reg, val);

        return 0;
}

/**
 * stm32_adc_get_trig_extsel() - Get external trigger selection
 * @trig: trigger
 *
 * Returns trigger extsel value, if trig matches, -EINVAL otherwise.
 */
static int stm32_adc_get_trig_extsel(struct iio_dev *indio_dev,
                                     struct iio_trigger *trig)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        int i;

        /* lookup triggers registered by stm32 timer trigger driver */
        for (i = 0; adc->cfg->trigs[i].name; i++) {
                /**
                 * Checking both stm32 timer trigger type and trig name
                 * should be safe against arbitrary trigger names.
                 */
                if (is_stm32_timer_trigger(trig) &&
                    !strcmp(adc->cfg->trigs[i].name, trig->name)) {
                        return adc->cfg->trigs[i].extsel;

                }
        }

        return -EINVAL;
}

/**
 * stm32_adc_set_trig() - Set a regular trigger
 * @indio_dev: IIO device
 * @trig: IIO trigger
 *
 * Set trigger source/polarity (e.g. SW, or HW with polarity) :
 * - if HW trigger disabled (e.g. trig == NULL, conversion launched by sw)
 * - if HW trigger enabled, set source & polarity
 */
static int stm32_adc_set_trig(struct iio_dev *indio_dev,
                              struct iio_trigger *trig)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        u32 val, extsel = 0, exten = STM32_EXTEN_SWTRIG;
        unsigned long flags;
        int ret;

        if (trig) {
                ret = stm32_adc_get_trig_extsel(indio_dev, trig);
                if (ret < 0)
                        return ret;

                /* set trigger source and polarity (default to rising edge) */
                extsel = ret;
                exten = adc->trigger_polarity + STM32_EXTEN_HWTRIG_RISING_EDGE;
        }

        spin_lock_irqsave(&adc->lock, flags);
        val = stm32_adc_readl(adc, adc->cfg->regs->exten.reg);
        val &= ~(adc->cfg->regs->exten.mask | adc->cfg->regs->extsel.mask);
        val |= exten << adc->cfg->regs->exten.shift;
        val |= extsel << adc->cfg->regs->extsel.shift;
        stm32_adc_writel(adc,  adc->cfg->regs->exten.reg, val);
        spin_unlock_irqrestore(&adc->lock, flags);

        return 0;
}

static int stm32_adc_set_trig_pol(struct iio_dev *indio_dev,
                                  const struct iio_chan_spec *chan,
                                  unsigned int type)
{
        struct stm32_adc *adc = iio_priv(indio_dev);

        adc->trigger_polarity = type;

        return 0;
}

static int stm32_adc_get_trig_pol(struct iio_dev *indio_dev,
                                  const struct iio_chan_spec *chan)
{
        struct stm32_adc *adc = iio_priv(indio_dev);

        return adc->trigger_polarity;
}

static const char * const stm32_trig_pol_items[] = {
        "rising-edge", "falling-edge", "both-edges",
};

static const struct iio_enum stm32_adc_trig_pol = {
        .items = stm32_trig_pol_items,
        .num_items = ARRAY_SIZE(stm32_trig_pol_items),
        .get = stm32_adc_get_trig_pol,
        .set = stm32_adc_set_trig_pol,
};

/**
 * stm32_adc_single_conv() - Performs a single conversion
 * @indio_dev: IIO device
 * @chan: IIO channel
 * @res: conversion result
 *
 * The function performs a single conversion on a given channel:
 * - Program sequencer with one channel (e.g. in SQ1 with len = 1)
 * - Use SW trigger
 * - Start conversion, then wait for interrupt completion.
 */
static int stm32_adc_single_conv(struct iio_dev *indio_dev,
                                 const struct iio_chan_spec *chan,
                                 int *res)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        const struct stm32_adc_regspec *regs = adc->cfg->regs;
        long timeout;
        u32 val;
        int ret;

        reinit_completion(&adc->completion);

        adc->bufi = 0;

        if (adc->cfg->prepare) {
                ret = adc->cfg->prepare(adc);
                if (ret)
                        return ret;
        }

        /* Program chan number in regular sequence (SQ1) */
        val = stm32_adc_readl(adc, regs->sqr[1].reg);
        val &= ~regs->sqr[1].mask;
        val |= chan->channel << regs->sqr[1].shift;
        stm32_adc_writel(adc, regs->sqr[1].reg, val);

        /* Set regular sequence len (0 for 1 conversion) */
        stm32_adc_clr_bits(adc, regs->sqr[0].reg, regs->sqr[0].mask);

        /* Trigger detection disabled (conversion can be launched in SW) */
        stm32_adc_clr_bits(adc, regs->exten.reg, regs->exten.mask);

        stm32_adc_conv_irq_enable(adc);

        adc->cfg->start_conv(adc, false);

        timeout = wait_for_completion_interruptible_timeout(
                                        &adc->completion, STM32_ADC_TIMEOUT);
        if (timeout == 0) {
                ret = -ETIMEDOUT;
        } else if (timeout < 0) {
                ret = timeout;
        } else {
                *res = adc->buffer[0];
                ret = IIO_VAL_INT;
        }

        adc->cfg->stop_conv(adc);

        stm32_adc_conv_irq_disable(adc);

        if (adc->cfg->unprepare)
                adc->cfg->unprepare(adc);

        return ret;
}

static int stm32_adc_read_raw(struct iio_dev *indio_dev,
                              struct iio_chan_spec const *chan,
                              int *val, int *val2, long mask)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                ret = iio_device_claim_direct_mode(indio_dev);
                if (ret)
                        return ret;
                if (chan->type == IIO_VOLTAGE)
                        ret = stm32_adc_single_conv(indio_dev, chan, val);
                else
                        ret = -EINVAL;
                iio_device_release_direct_mode(indio_dev);
                return ret;

        case IIO_CHAN_INFO_SCALE:
                *val = adc->common->vref_mv;
                *val2 = chan->scan_type.realbits;
                return IIO_VAL_FRACTIONAL_LOG2;

        default:
                return -EINVAL;
        }
}

static irqreturn_t stm32_adc_isr(int irq, void *data)
{
        struct stm32_adc *adc = data;
        struct iio_dev *indio_dev = iio_priv_to_dev(adc);
        const struct stm32_adc_regspec *regs = adc->cfg->regs;
        u32 status = stm32_adc_readl(adc, regs->isr_eoc.reg);

        if (status & regs->isr_eoc.mask) {
                /* Reading DR also clears EOC status flag */
                adc->buffer[adc->bufi] = stm32_adc_readw(adc, regs->dr);
                if (iio_buffer_enabled(indio_dev)) {
                        adc->bufi++;
                        if (adc->bufi >= adc->num_conv) {
                                stm32_adc_conv_irq_disable(adc);
                                iio_trigger_poll(indio_dev->trig);
                        }
                } else {
                        complete(&adc->completion);
                }
                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

/**
 * stm32_adc_validate_trigger() - validate trigger for stm32 adc
 * @indio_dev: IIO device
 * @trig: new trigger
 *
 * Returns: 0 if trig matches one of the triggers registered by stm32 adc
 * driver, -EINVAL otherwise.
 */
static int stm32_adc_validate_trigger(struct iio_dev *indio_dev,
                                      struct iio_trigger *trig)
{
        return stm32_adc_get_trig_extsel(indio_dev, trig) < 0 ? -EINVAL : 0;
}

static int stm32_adc_set_watermark(struct iio_dev *indio_dev, unsigned int val)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        unsigned int watermark = STM32_DMA_BUFFER_SIZE / 2;

        /*
         * dma cyclic transfers are used, buffer is split into two periods.
         * There should be :
         * - always one buffer (period) dma is working on
         * - one buffer (period) driver can push with iio_trigger_poll().
         */
        watermark = min(watermark, val * (unsigned)(sizeof(u16)));
        adc->rx_buf_sz = watermark * 2;

        return 0;
}

static int stm32_adc_update_scan_mode(struct iio_dev *indio_dev,
                                      const unsigned long *scan_mask)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        int ret;

        adc->num_conv = bitmap_weight(scan_mask, indio_dev->masklength);

        ret = stm32_adc_conf_scan_seq(indio_dev, scan_mask);
        if (ret)
                return ret;

        return 0;
}

static int stm32_adc_of_xlate(struct iio_dev *indio_dev,
                              const struct of_phandle_args *iiospec)
{
        int i;

        for (i = 0; i < indio_dev->num_channels; i++)
                if (indio_dev->channels[i].channel == iiospec->args[0])
                        return i;

        return -EINVAL;
}

/**
 * stm32_adc_debugfs_reg_access - read or write register value
 *
 * To read a value from an ADC register:
 *   echo [ADC reg offset] > direct_reg_access
 *   cat direct_reg_access
 *
 * To write a value in a ADC register:
 *   echo [ADC_reg_offset] [value] > direct_reg_access
 */
static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev,
                                        unsigned reg, unsigned writeval,
                                        unsigned *readval)
{
        struct stm32_adc *adc = iio_priv(indio_dev);

        if (!readval)
                stm32_adc_writel(adc, reg, writeval);
        else
                *readval = stm32_adc_readl(adc, reg);

        return 0;
}

static const struct iio_info stm32_adc_iio_info = {
        .read_raw = stm32_adc_read_raw,
        .validate_trigger = stm32_adc_validate_trigger,
        .hwfifo_set_watermark = stm32_adc_set_watermark,
        .update_scan_mode = stm32_adc_update_scan_mode,
        .debugfs_reg_access = stm32_adc_debugfs_reg_access,
        .of_xlate = stm32_adc_of_xlate,
        .driver_module = THIS_MODULE,
};

static unsigned int stm32_adc_dma_residue(struct stm32_adc *adc)
{
        struct dma_tx_state state;
        enum dma_status status;

        status = dmaengine_tx_status(adc->dma_chan,
                                     adc->dma_chan->cookie,
                                     &state);
        if (status == DMA_IN_PROGRESS) {
                /* Residue is size in bytes from end of buffer */
                unsigned int i = adc->rx_buf_sz - state.residue;
                unsigned int size;

                /* Return available bytes */
                if (i >= adc->bufi)
                        size = i - adc->bufi;
                else
                        size = adc->rx_buf_sz + i - adc->bufi;

                return size;
        }

        return 0;
}

static void stm32_adc_dma_buffer_done(void *data)
{
        struct iio_dev *indio_dev = data;

        iio_trigger_poll_chained(indio_dev->trig);
}

static int stm32_adc_dma_start(struct iio_dev *indio_dev)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        struct dma_async_tx_descriptor *desc;
        dma_cookie_t cookie;
        int ret;

        if (!adc->dma_chan)
                return 0;

        dev_dbg(&indio_dev->dev, "%s size=%d watermark=%d\n", __func__,
                adc->rx_buf_sz, adc->rx_buf_sz / 2);

        /* Prepare a DMA cyclic transaction */
        desc = dmaengine_prep_dma_cyclic(adc->dma_chan,
                                         adc->rx_dma_buf,
                                         adc->rx_buf_sz, adc->rx_buf_sz / 2,
                                         DMA_DEV_TO_MEM,
                                         DMA_PREP_INTERRUPT);
        if (!desc)
                return -EBUSY;

        desc->callback = stm32_adc_dma_buffer_done;
        desc->callback_param = indio_dev;

        cookie = dmaengine_submit(desc);
        ret = dma_submit_error(cookie);
        if (ret) {
                dmaengine_terminate_all(adc->dma_chan);
                return ret;
        }

        /* Issue pending DMA requests */
        dma_async_issue_pending(adc->dma_chan);

        return 0;
}

static int stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        int ret;

        if (adc->cfg->prepare) {
                ret = adc->cfg->prepare(adc);
                if (ret)
                        return ret;
        }

        ret = stm32_adc_set_trig(indio_dev, indio_dev->trig);
        if (ret) {
                dev_err(&indio_dev->dev, "Can't set trigger\n");
                goto err_unprepare;
        }

        ret = stm32_adc_dma_start(indio_dev);
        if (ret) {
                dev_err(&indio_dev->dev, "Can't start dma\n");
                goto err_clr_trig;
        }

        ret = iio_triggered_buffer_postenable(indio_dev);
        if (ret < 0)
                goto err_stop_dma;

        /* Reset adc buffer index */
        adc->bufi = 0;

        if (!adc->dma_chan)
                stm32_adc_conv_irq_enable(adc);

        adc->cfg->start_conv(adc, !!adc->dma_chan);

        return 0;

err_stop_dma:
        if (adc->dma_chan)
                dmaengine_terminate_all(adc->dma_chan);
err_clr_trig:
        stm32_adc_set_trig(indio_dev, NULL);
err_unprepare:
        if (adc->cfg->unprepare)
                adc->cfg->unprepare(adc);

        return ret;
}

static int stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        int ret;

        adc->cfg->stop_conv(adc);
        if (!adc->dma_chan)
                stm32_adc_conv_irq_disable(adc);

        ret = iio_triggered_buffer_predisable(indio_dev);
        if (ret < 0)
                dev_err(&indio_dev->dev, "predisable failed\n");

        if (adc->dma_chan)
                dmaengine_terminate_all(adc->dma_chan);

        if (stm32_adc_set_trig(indio_dev, NULL))
                dev_err(&indio_dev->dev, "Can't clear trigger\n");

        if (adc->cfg->unprepare)
                adc->cfg->unprepare(adc);

        return ret;
}

static const struct iio_buffer_setup_ops stm32_adc_buffer_setup_ops = {
        .postenable = &stm32_adc_buffer_postenable,
        .predisable = &stm32_adc_buffer_predisable,
};

static irqreturn_t stm32_adc_trigger_handler(int irq, void *p)
{
        struct iio_poll_func *pf = p;
        struct iio_dev *indio_dev = pf->indio_dev;
        struct stm32_adc *adc = iio_priv(indio_dev);

        dev_dbg(&indio_dev->dev, "%s bufi=%d\n", __func__, adc->bufi);

        if (!adc->dma_chan) {
                /* reset buffer index */
                adc->bufi = 0;
                iio_push_to_buffers_with_timestamp(indio_dev, adc->buffer,
                                                   pf->timestamp);
        } else {
                int residue = stm32_adc_dma_residue(adc);

                while (residue >= indio_dev->scan_bytes) {
                        u16 *buffer = (u16 *)&adc->rx_buf[adc->bufi];

                        iio_push_to_buffers_with_timestamp(indio_dev, buffer,
                                                           pf->timestamp);
                        residue -= indio_dev->scan_bytes;
                        adc->bufi += indio_dev->scan_bytes;
                        if (adc->bufi >= adc->rx_buf_sz)
                                adc->bufi = 0;
                }
        }

        iio_trigger_notify_done(indio_dev->trig);

        /* re-enable eoc irq */
        if (!adc->dma_chan)
                stm32_adc_conv_irq_enable(adc);

        return IRQ_HANDLED;
}

static const struct iio_chan_spec_ext_info stm32_adc_ext_info[] = {
        IIO_ENUM("trigger_polarity", IIO_SHARED_BY_ALL, &stm32_adc_trig_pol),
        {
                .name = "trigger_polarity_available",
                .shared = IIO_SHARED_BY_ALL,
                .read = iio_enum_available_read,
                .private = (uintptr_t)&stm32_adc_trig_pol,
        },
        {},
};

static int stm32_adc_of_get_resolution(struct iio_dev *indio_dev)
{
        struct device_node *node = indio_dev->dev.of_node;
        struct stm32_adc *adc = iio_priv(indio_dev);
        unsigned int i;
        u32 res;

        if (of_property_read_u32(node, "assigned-resolution-bits", &res))
                res = adc->cfg->adc_info->resolutions[0];

        for (i = 0; i < adc->cfg->adc_info->num_res; i++)
                if (res == adc->cfg->adc_info->resolutions[i])
                        break;
        if (i >= adc->cfg->adc_info->num_res) {
                dev_err(&indio_dev->dev, "Bad resolution: %u bits\n", res);
                return -EINVAL;
        }

        dev_dbg(&indio_dev->dev, "Using %u bits resolution\n", res);
        adc->res = i;

        return 0;
}

static void stm32_adc_chan_init_one(struct iio_dev *indio_dev,
                                    struct iio_chan_spec *chan,
                                    const struct stm32_adc_chan_spec *channel,
                                    int scan_index)
{
        struct stm32_adc *adc = iio_priv(indio_dev);

        chan->type = channel->type;
        chan->channel = channel->channel;
        chan->datasheet_name = channel->name;
        chan->scan_index = scan_index;
        chan->indexed = 1;
        chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
        chan->info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE);
        chan->scan_type.sign = 'u';
        chan->scan_type.realbits = adc->cfg->adc_info->resolutions[adc->res];
        chan->scan_type.storagebits = 16;
        chan->ext_info = stm32_adc_ext_info;

        /* pre-build selected channels mask */
        adc->pcsel |= BIT(chan->channel);
}

static int stm32_adc_chan_of_init(struct iio_dev *indio_dev)
{
        struct device_node *node = indio_dev->dev.of_node;
        struct stm32_adc *adc = iio_priv(indio_dev);
        const struct stm32_adc_info *adc_info = adc->cfg->adc_info;
        struct property *prop;
        const __be32 *cur;
        struct iio_chan_spec *channels;
        int scan_index = 0, num_channels;
        u32 val;

        num_channels = of_property_count_u32_elems(node, "st,adc-channels");
        if (num_channels < 0 ||
            num_channels >= adc_info->max_channels) {
                dev_err(&indio_dev->dev, "Bad st,adc-channels?\n");
                return num_channels < 0 ? num_channels : -EINVAL;
        }

        channels = devm_kcalloc(&indio_dev->dev, num_channels,
                                sizeof(struct iio_chan_spec), GFP_KERNEL);
        if (!channels)
                return -ENOMEM;

        of_property_for_each_u32(node, "st,adc-channels", prop, cur, val) {
                if (val >= adc_info->max_channels) {
                        dev_err(&indio_dev->dev, "Invalid channel %d\n", val);
                        return -EINVAL;
                }
                stm32_adc_chan_init_one(indio_dev, &channels[scan_index],
                                        &adc_info->channels[val],
                                        scan_index);
                scan_index++;
        }

        indio_dev->num_channels = scan_index;
        indio_dev->channels = channels;

        return 0;
}

static int stm32_adc_dma_request(struct iio_dev *indio_dev)
{
        struct stm32_adc *adc = iio_priv(indio_dev);
        struct dma_slave_config config;
        int ret;

        adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
        if (!adc->dma_chan)
                return 0;

        adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
                                         STM32_DMA_BUFFER_SIZE,
                                         &adc->rx_dma_buf, GFP_KERNEL);
        if (!adc->rx_buf) {
                ret = -ENOMEM;
                goto err_release;
        }

        /* Configure DMA channel to read data register */
        memset(&config, 0, sizeof(config));
        config.src_addr = (dma_addr_t)adc->common->phys_base;
        config.src_addr += adc->offset + adc->cfg->regs->dr;
        config.src_addr_width = DMA_SLAVE_BUSWIDTH_2_BYTES;

        ret = dmaengine_slave_config(adc->dma_chan, &config);
        if (ret)
                goto err_free;

        return 0;

err_free:
        dma_free_coherent(adc->dma_chan->device->dev, STM32_DMA_BUFFER_SIZE,
                          adc->rx_buf, adc->rx_dma_buf);
err_release:
        dma_release_channel(adc->dma_chan);

        return ret;
}

static int stm32_adc_probe(struct platform_device *pdev)
{
        struct iio_dev *indio_dev;
        struct device *dev = &pdev->dev;
        struct stm32_adc *adc;
        int ret;

        if (!pdev->dev.of_node)
                return -ENODEV;

        indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*adc));
        if (!indio_dev)
                return -ENOMEM;

        adc = iio_priv(indio_dev);
        adc->common = dev_get_drvdata(pdev->dev.parent);
        spin_lock_init(&adc->lock);
        init_completion(&adc->completion);
        adc->cfg = (const struct stm32_adc_cfg *)
                of_match_device(dev->driver->of_match_table, dev)->data;

        indio_dev->name = dev_name(&pdev->dev);
        indio_dev->dev.parent = &pdev->dev;
        indio_dev->dev.of_node = pdev->dev.of_node;
        indio_dev->info = &stm32_adc_iio_info;
        indio_dev->modes = INDIO_DIRECT_MODE;

        platform_set_drvdata(pdev, adc);

        ret = of_property_read_u32(pdev->dev.of_node, "reg", &adc->offset);
        if (ret != 0) {
                dev_err(&pdev->dev, "missing reg property\n");
                return -EINVAL;
        }

        adc->irq = platform_get_irq(pdev, 0);
        if (adc->irq < 0) {
                dev_err(&pdev->dev, "failed to get irq\n");
                return adc->irq;
        }

        ret = devm_request_irq(&pdev->dev, adc->irq, stm32_adc_isr,
                               0, pdev->name, adc);
        if (ret) {
                dev_err(&pdev->dev, "failed to request IRQ\n");
                return ret;
        }

        adc->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(adc->clk)) {
                ret = PTR_ERR(adc->clk);
                if (ret == -ENOENT && !adc->cfg->clk_required) {
                        adc->clk = NULL;
                } else {
                        dev_err(&pdev->dev, "Can't get clock\n");
                        return ret;
                }
        }

        if (adc->clk) {
                ret = clk_prepare_enable(adc->clk);
                if (ret < 0) {
                        dev_err(&pdev->dev, "clk enable failed\n");
                        return ret;
                }
        }

        ret = stm32_adc_of_get_resolution(indio_dev);
        if (ret < 0)
                goto err_clk_disable;
        stm32_adc_set_res(adc);

        if (adc->cfg->selfcalib) {
                ret = adc->cfg->selfcalib(adc);
                if (ret)
                        goto err_clk_disable;
        }

        ret = stm32_adc_chan_of_init(indio_dev);
        if (ret < 0)
                goto err_clk_disable;

        ret = stm32_adc_dma_request(indio_dev);
        if (ret < 0)
                goto err_clk_disable;

        ret = iio_triggered_buffer_setup(indio_dev,
                                         &iio_pollfunc_store_time,
                                         &stm32_adc_trigger_handler,
                                         &stm32_adc_buffer_setup_ops);
        if (ret) {
                dev_err(&pdev->dev, "buffer setup failed\n");
                goto err_dma_disable;
        }

        ret = iio_device_register(indio_dev);
        if (ret) {
                dev_err(&pdev->dev, "iio dev register failed\n");
                goto err_buffer_cleanup;
        }

        return 0;

err_buffer_cleanup:
        iio_triggered_buffer_cleanup(indio_dev);

err_dma_disable:
        if (adc->dma_chan) {
                dma_free_coherent(adc->dma_chan->device->dev,
                                  STM32_DMA_BUFFER_SIZE,
                                  adc->rx_buf, adc->rx_dma_buf);
                dma_release_channel(adc->dma_chan);
        }
err_clk_disable:
        if (adc->clk)
                clk_disable_unprepare(adc->clk);

        return ret;
}

static int stm32_adc_remove(struct platform_device *pdev)
{
        struct stm32_adc *adc = platform_get_drvdata(pdev);
        struct iio_dev *indio_dev = iio_priv_to_dev(adc);

        iio_device_unregister(indio_dev);
        iio_triggered_buffer_cleanup(indio_dev);
        if (adc->dma_chan) {
                dma_free_coherent(adc->dma_chan->device->dev,
                                  STM32_DMA_BUFFER_SIZE,
                                  adc->rx_buf, adc->rx_dma_buf);
                dma_release_channel(adc->dma_chan);
        }
        if (adc->clk)
                clk_disable_unprepare(adc->clk);

        return 0;
}

static const struct stm32_adc_cfg stm32f4_adc_cfg = {
        .regs = &stm32f4_adc_regspec,
        .adc_info = &stm32f4_adc_info,
        .trigs = stm32f4_adc_trigs,
        .clk_required = true,
        .start_conv = stm32f4_adc_start_conv,
        .stop_conv = stm32f4_adc_stop_conv,
};

static const struct stm32_adc_cfg stm32h7_adc_cfg = {
        .regs = &stm32h7_adc_regspec,
        .adc_info = &stm32h7_adc_info,
        .trigs = stm32h7_adc_trigs,
        .selfcalib = stm32h7_adc_selfcalib,
        .start_conv = stm32h7_adc_start_conv,
        .stop_conv = stm32h7_adc_stop_conv,
        .prepare = stm32h7_adc_prepare,
        .unprepare = stm32h7_adc_unprepare,
};

static const struct of_device_id stm32_adc_of_match[] = {
        { .compatible = "st,stm32f4-adc", .data = (void *)&stm32f4_adc_cfg },
        { .compatible = "st,stm32h7-adc", .data = (void *)&stm32h7_adc_cfg },
        {},
};
MODULE_DEVICE_TABLE(of, stm32_adc_of_match);

static struct platform_driver stm32_adc_driver = {
        .probe = stm32_adc_probe,
        .remove = stm32_adc_remove,
        .driver = {
                .name = "stm32-adc",
                .of_match_table = stm32_adc_of_match,
        },
};
module_platform_driver(stm32_adc_driver);

MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
MODULE_DESCRIPTION("STMicroelectronics STM32 ADC IIO driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:stm32-adc");