// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for STM32 DMA controller
 *
 * Inspired by dma-jz4740.c and tegra20-apb-dma.c
 *
 * Copyright (C) M'boumba Cedric Madianga 2015
 * Author: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
 *         Pierre-Yves Mordret <pierre-yves.mordret@st.com>
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_dma.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/reset.h>
#include <linux/sched.h>
#include <linux/slab.h>

#include "virt-dma.h"

#define STM32_DMA_LISR                  0x0000 /* DMA Low Int Status Reg */
#define STM32_DMA_HISR                  0x0004 /* DMA High Int Status Reg */
#define STM32_DMA_LIFCR                 0x0008 /* DMA Low Int Flag Clear Reg */
#define STM32_DMA_HIFCR                 0x000c /* DMA High Int Flag Clear Reg */
#define STM32_DMA_TCI                   BIT(5) /* Transfer Complete Interrupt */
#define STM32_DMA_HTI                   BIT(4) /* Half Transfer Interrupt */
#define STM32_DMA_TEI                   BIT(3) /* Transfer Error Interrupt */
#define STM32_DMA_DMEI                  BIT(2) /* Direct Mode Error Interrupt */
#define STM32_DMA_FEI                   BIT(0) /* FIFO Error Interrupt */
#define STM32_DMA_MASKI                 (STM32_DMA_TCI \
                                         | STM32_DMA_TEI \
                                         | STM32_DMA_DMEI \
                                         | STM32_DMA_FEI)

/* DMA Stream x Configuration Register */
#define STM32_DMA_SCR(x)                (0x0010 + 0x18 * (x)) /* x = 0..7 */
#define STM32_DMA_SCR_REQ(n)            ((n & 0x7) << 25)
#define STM32_DMA_SCR_MBURST_MASK       GENMASK(24, 23)
#define STM32_DMA_SCR_MBURST(n)         ((n & 0x3) << 23)
#define STM32_DMA_SCR_PBURST_MASK       GENMASK(22, 21)
#define STM32_DMA_SCR_PBURST(n)         ((n & 0x3) << 21)
#define STM32_DMA_SCR_PL_MASK           GENMASK(17, 16)
#define STM32_DMA_SCR_PL(n)             ((n & 0x3) << 16)
#define STM32_DMA_SCR_MSIZE_MASK        GENMASK(14, 13)
#define STM32_DMA_SCR_MSIZE(n)          ((n & 0x3) << 13)
#define STM32_DMA_SCR_PSIZE_MASK        GENMASK(12, 11)
#define STM32_DMA_SCR_PSIZE(n)          ((n & 0x3) << 11)
#define STM32_DMA_SCR_PSIZE_GET(n)      ((n & STM32_DMA_SCR_PSIZE_MASK) >> 11)
#define STM32_DMA_SCR_DIR_MASK          GENMASK(7, 6)
#define STM32_DMA_SCR_DIR(n)            ((n & 0x3) << 6)
#define STM32_DMA_SCR_CT                BIT(19) /* Target in double buffer */
#define STM32_DMA_SCR_DBM               BIT(18) /* Double Buffer Mode */
#define STM32_DMA_SCR_PINCOS            BIT(15) /* Peripheral inc offset size */
#define STM32_DMA_SCR_MINC              BIT(10) /* Memory increment mode */
#define STM32_DMA_SCR_PINC              BIT(9) /* Peripheral increment mode */
#define STM32_DMA_SCR_CIRC              BIT(8) /* Circular mode */
#define STM32_DMA_SCR_PFCTRL            BIT(5) /* Peripheral Flow Controller */
#define STM32_DMA_SCR_TCIE              BIT(4) /* Transfer Complete Int Enable
                                                */
#define STM32_DMA_SCR_TEIE              BIT(2) /* Transfer Error Int Enable */
#define STM32_DMA_SCR_DMEIE             BIT(1) /* Direct Mode Err Int Enable */
#define STM32_DMA_SCR_EN                BIT(0) /* Stream Enable */
#define STM32_DMA_SCR_CFG_MASK          (STM32_DMA_SCR_PINC \
                                        | STM32_DMA_SCR_MINC \
                                        | STM32_DMA_SCR_PINCOS \
                                        | STM32_DMA_SCR_PL_MASK)
#define STM32_DMA_SCR_IRQ_MASK          (STM32_DMA_SCR_TCIE \
                                        | STM32_DMA_SCR_TEIE \
                                        | STM32_DMA_SCR_DMEIE)

/* DMA Stream x number of data register */
#define STM32_DMA_SNDTR(x)              (0x0014 + 0x18 * (x))

/* DMA stream peripheral address register */
#define STM32_DMA_SPAR(x)               (0x0018 + 0x18 * (x))

/* DMA stream x memory 0 address register */
#define STM32_DMA_SM0AR(x)              (0x001c + 0x18 * (x))

/* DMA stream x memory 1 address register */
#define STM32_DMA_SM1AR(x)              (0x0020 + 0x18 * (x))

/* DMA stream x FIFO control register */
#define STM32_DMA_SFCR(x)               (0x0024 + 0x18 * (x))
#define STM32_DMA_SFCR_FTH_MASK         GENMASK(1, 0)
#define STM32_DMA_SFCR_FTH(n)           (n & STM32_DMA_SFCR_FTH_MASK)
#define STM32_DMA_SFCR_FEIE             BIT(7) /* FIFO error interrupt enable */
#define STM32_DMA_SFCR_DMDIS            BIT(2) /* Direct mode disable */
#define STM32_DMA_SFCR_MASK             (STM32_DMA_SFCR_FEIE \
                                        | STM32_DMA_SFCR_DMDIS)

/* DMA direction */
#define STM32_DMA_DEV_TO_MEM            0x00
#define STM32_DMA_MEM_TO_DEV            0x01
#define STM32_DMA_MEM_TO_MEM            0x02

/* DMA priority level */
#define STM32_DMA_PRIORITY_LOW          0x00
#define STM32_DMA_PRIORITY_MEDIUM       0x01
#define STM32_DMA_PRIORITY_HIGH         0x02
#define STM32_DMA_PRIORITY_VERY_HIGH    0x03

/* DMA FIFO threshold selection */
#define STM32_DMA_FIFO_THRESHOLD_1QUARTERFULL           0x00
#define STM32_DMA_FIFO_THRESHOLD_HALFFULL               0x01
#define STM32_DMA_FIFO_THRESHOLD_3QUARTERSFULL          0x02
#define STM32_DMA_FIFO_THRESHOLD_FULL                   0x03

#define STM32_DMA_MAX_DATA_ITEMS        0xffff
/*
 * Valid transfer starts from @0 to @0xFFFE leading to unaligned scatter
 * gather at boundary. Thus it's safer to round down this value on FIFO
 * size (16 Bytes)
 */
#define STM32_DMA_ALIGNED_MAX_DATA_ITEMS        \
        ALIGN_DOWN(STM32_DMA_MAX_DATA_ITEMS, 16)
#define STM32_DMA_MAX_CHANNELS          0x08
#define STM32_DMA_MAX_REQUEST_ID        0x08
#define STM32_DMA_MAX_DATA_PARAM        0x03
#define STM32_DMA_FIFO_SIZE             16      /* FIFO is 16 bytes */
#define STM32_DMA_MIN_BURST             4
#define STM32_DMA_MAX_BURST             16

/* DMA Features */
#define STM32_DMA_THRESHOLD_FTR_MASK    GENMASK(1, 0)
#define STM32_DMA_THRESHOLD_FTR_GET(n)  ((n) & STM32_DMA_THRESHOLD_FTR_MASK)

enum stm32_dma_width {
        STM32_DMA_BYTE,
        STM32_DMA_HALF_WORD,
        STM32_DMA_WORD,
};

enum stm32_dma_burst_size {
        STM32_DMA_BURST_SINGLE,
        STM32_DMA_BURST_INCR4,
        STM32_DMA_BURST_INCR8,
        STM32_DMA_BURST_INCR16,
};

/**
 * struct stm32_dma_cfg - STM32 DMA custom configuration
 * @channel_id: channel ID
 * @request_line: DMA request
 * @stream_config: 32bit mask specifying the DMA channel configuration
 * @features: 32bit mask specifying the DMA Feature list
 */
struct stm32_dma_cfg {
        u32 channel_id;
        u32 request_line;
        u32 stream_config;
        u32 features;
};

struct stm32_dma_chan_reg {
        u32 dma_lisr;
        u32 dma_hisr;
        u32 dma_lifcr;
        u32 dma_hifcr;
        u32 dma_scr;
        u32 dma_sndtr;
        u32 dma_spar;
        u32 dma_sm0ar;
        u32 dma_sm1ar;
        u32 dma_sfcr;
};

struct stm32_dma_sg_req {
        u32 len;
        struct stm32_dma_chan_reg chan_reg;
};

struct stm32_dma_desc {
        struct virt_dma_desc vdesc;
        bool cyclic;
        u32 num_sgs;
        struct stm32_dma_sg_req sg_req[];
};

struct stm32_dma_chan {
        struct virt_dma_chan vchan;
        bool config_init;
        bool busy;
        u32 id;
        u32 irq;
        struct stm32_dma_desc *desc;
        u32 next_sg;
        struct dma_slave_config dma_sconfig;
        struct stm32_dma_chan_reg chan_reg;
        u32 threshold;
        u32 mem_burst;
        u32 mem_width;
};

struct stm32_dma_device {
        struct dma_device ddev;
        void __iomem *base;
        struct clk *clk;
        struct reset_control *rst;
        bool mem2mem;
        struct stm32_dma_chan chan[STM32_DMA_MAX_CHANNELS];
};

static struct stm32_dma_device *stm32_dma_get_dev(struct stm32_dma_chan *chan)
{
        return container_of(chan->vchan.chan.device, struct stm32_dma_device,
                            ddev);
}

static struct stm32_dma_chan *to_stm32_dma_chan(struct dma_chan *c)
{
        return container_of(c, struct stm32_dma_chan, vchan.chan);
}

static struct stm32_dma_desc *to_stm32_dma_desc(struct virt_dma_desc *vdesc)
{
        return container_of(vdesc, struct stm32_dma_desc, vdesc);
}

static struct device *chan2dev(struct stm32_dma_chan *chan)
{
        return &chan->vchan.chan.dev->device;
}

static u32 stm32_dma_read(struct stm32_dma_device *dmadev, u32 reg)
{
        return readl_relaxed(dmadev->base + reg);
}

static void stm32_dma_write(struct stm32_dma_device *dmadev, u32 reg, u32 val)
{
        writel_relaxed(val, dmadev->base + reg);
}

static struct stm32_dma_desc *stm32_dma_alloc_desc(u32 num_sgs)
{
        return kzalloc(sizeof(struct stm32_dma_desc) +
                       sizeof(struct stm32_dma_sg_req) * num_sgs, GFP_NOWAIT);
}

static int stm32_dma_get_width(struct stm32_dma_chan *chan,
                               enum dma_slave_buswidth width)
{
        switch (width) {
        case DMA_SLAVE_BUSWIDTH_1_BYTE:
                return STM32_DMA_BYTE;
        case DMA_SLAVE_BUSWIDTH_2_BYTES:
                return STM32_DMA_HALF_WORD;
        case DMA_SLAVE_BUSWIDTH_4_BYTES:
                return STM32_DMA_WORD;
        default:
                dev_err(chan2dev(chan), "Dma bus width not supported\n");
                return -EINVAL;
        }
}

static enum dma_slave_buswidth stm32_dma_get_max_width(u32 buf_len,
                                                       u32 threshold)
{
        enum dma_slave_buswidth max_width;

        if (threshold == STM32_DMA_FIFO_THRESHOLD_FULL)
                max_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
        else
                max_width = DMA_SLAVE_BUSWIDTH_2_BYTES;

        while ((buf_len < max_width  || buf_len % max_width) &&
               max_width > DMA_SLAVE_BUSWIDTH_1_BYTE)
                max_width = max_width >> 1;

        return max_width;
}

static bool stm32_dma_fifo_threshold_is_allowed(u32 burst, u32 threshold,
                                                enum dma_slave_buswidth width)
{
        u32 remaining;

        if (width != DMA_SLAVE_BUSWIDTH_UNDEFINED) {
                if (burst != 0) {
                        /*
                         * If number of beats fit in several whole bursts
                         * this configuration is allowed.
                         */
                        remaining = ((STM32_DMA_FIFO_SIZE / width) *
                                     (threshold + 1) / 4) % burst;

                        if (remaining == 0)
                                return true;
                } else {
                        return true;
                }
        }

        return false;
}

static bool stm32_dma_is_burst_possible(u32 buf_len, u32 threshold)
{
        /*
         * Buffer or period length has to be aligned on FIFO depth.
         * Otherwise bytes may be stuck within FIFO at buffer or period
         * length.
         */
        return ((buf_len % ((threshold + 1) * 4)) == 0);
}

static u32 stm32_dma_get_best_burst(u32 buf_len, u32 max_burst, u32 threshold,
                                    enum dma_slave_buswidth width)
{
        u32 best_burst = max_burst;

        if (best_burst == 1 || !stm32_dma_is_burst_possible(buf_len, threshold))
                return 0;

        while ((buf_len < best_burst * width && best_burst > 1) ||
               !stm32_dma_fifo_threshold_is_allowed(best_burst, threshold,
                                                    width)) {
                if (best_burst > STM32_DMA_MIN_BURST)
                        best_burst = best_burst >> 1;
                else
                        best_burst = 0;
        }

        return best_burst;
}

static int stm32_dma_get_burst(struct stm32_dma_chan *chan, u32 maxburst)
{
        switch (maxburst) {
        case 0:
        case 1:
                return STM32_DMA_BURST_SINGLE;
        case 4:
                return STM32_DMA_BURST_INCR4;
        case 8:
                return STM32_DMA_BURST_INCR8;
        case 16:
                return STM32_DMA_BURST_INCR16;
        default:
                dev_err(chan2dev(chan), "Dma burst size not supported\n");
                return -EINVAL;
        }
}

static void stm32_dma_set_fifo_config(struct stm32_dma_chan *chan,
                                      u32 src_burst, u32 dst_burst)
{
        chan->chan_reg.dma_sfcr &= ~STM32_DMA_SFCR_MASK;
        chan->chan_reg.dma_scr &= ~STM32_DMA_SCR_DMEIE;

        if (!src_burst && !dst_burst) {
                /* Using direct mode */
                chan->chan_reg.dma_scr |= STM32_DMA_SCR_DMEIE;
        } else {
                /* Using FIFO mode */
                chan->chan_reg.dma_sfcr |= STM32_DMA_SFCR_MASK;
        }
}

static int stm32_dma_slave_config(struct dma_chan *c,
                                  struct dma_slave_config *config)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);

        memcpy(&chan->dma_sconfig, config, sizeof(*config));

        chan->config_init = true;

        return 0;
}

static u32 stm32_dma_irq_status(struct stm32_dma_chan *chan)
{
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        u32 flags, dma_isr;

        /*
         * Read "flags" from DMA_xISR register corresponding to the selected
         * DMA channel at the correct bit offset inside that register.
         *
         * If (ch % 4) is 2 or 3, left shift the mask by 16 bits.
         * If (ch % 4) is 1 or 3, additionally left shift the mask by 6 bits.
         */

        if (chan->id & 4)
                dma_isr = stm32_dma_read(dmadev, STM32_DMA_HISR);
        else
                dma_isr = stm32_dma_read(dmadev, STM32_DMA_LISR);

        flags = dma_isr >> (((chan->id & 2) << 3) | ((chan->id & 1) * 6));

        return flags & STM32_DMA_MASKI;
}

static void stm32_dma_irq_clear(struct stm32_dma_chan *chan, u32 flags)
{
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        u32 dma_ifcr;

        /*
         * Write "flags" to the DMA_xIFCR register corresponding to the selected
         * DMA channel at the correct bit offset inside that register.
         *
         * If (ch % 4) is 2 or 3, left shift the mask by 16 bits.
         * If (ch % 4) is 1 or 3, additionally left shift the mask by 6 bits.
         */
        flags &= STM32_DMA_MASKI;
        dma_ifcr = flags << (((chan->id & 2) << 3) | ((chan->id & 1) * 6));

        if (chan->id & 4)
                stm32_dma_write(dmadev, STM32_DMA_HIFCR, dma_ifcr);
        else
                stm32_dma_write(dmadev, STM32_DMA_LIFCR, dma_ifcr);
}

static int stm32_dma_disable_chan(struct stm32_dma_chan *chan)
{
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        unsigned long timeout = jiffies + msecs_to_jiffies(5000);
        u32 dma_scr, id;

        id = chan->id;
        dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));

        if (dma_scr & STM32_DMA_SCR_EN) {
                dma_scr &= ~STM32_DMA_SCR_EN;
                stm32_dma_write(dmadev, STM32_DMA_SCR(id), dma_scr);

                do {
                        dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));
                        dma_scr &= STM32_DMA_SCR_EN;
                        if (!dma_scr)
                                break;

                        if (time_after_eq(jiffies, timeout)) {
                                dev_err(chan2dev(chan), "%s: timeout!\n",
                                        __func__);
                                return -EBUSY;
                        }
                        cond_resched();
                } while (1);
        }

        return 0;
}

static void stm32_dma_stop(struct stm32_dma_chan *chan)
{
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        u32 dma_scr, dma_sfcr, status;
        int ret;

        /* Disable interrupts */
        dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
        dma_scr &= ~STM32_DMA_SCR_IRQ_MASK;
        stm32_dma_write(dmadev, STM32_DMA_SCR(chan->id), dma_scr);
        dma_sfcr = stm32_dma_read(dmadev, STM32_DMA_SFCR(chan->id));
        dma_sfcr &= ~STM32_DMA_SFCR_FEIE;
        stm32_dma_write(dmadev, STM32_DMA_SFCR(chan->id), dma_sfcr);

        /* Disable DMA */
        ret = stm32_dma_disable_chan(chan);
        if (ret < 0)
                return;

        /* Clear interrupt status if it is there */
        status = stm32_dma_irq_status(chan);
        if (status) {
                dev_dbg(chan2dev(chan), "%s(): clearing interrupt: 0x%08x\n",
                        __func__, status);
                stm32_dma_irq_clear(chan, status);
        }

        chan->busy = false;
}

static int stm32_dma_terminate_all(struct dma_chan *c)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        unsigned long flags;
        LIST_HEAD(head);

        spin_lock_irqsave(&chan->vchan.lock, flags);

        if (chan->busy) {
                stm32_dma_stop(chan);
                chan->desc = NULL;
        }

        vchan_get_all_descriptors(&chan->vchan, &head);
        spin_unlock_irqrestore(&chan->vchan.lock, flags);
        vchan_dma_desc_free_list(&chan->vchan, &head);

        return 0;
}

static void stm32_dma_synchronize(struct dma_chan *c)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);

        vchan_synchronize(&chan->vchan);
}

static void stm32_dma_dump_reg(struct stm32_dma_chan *chan)
{
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        u32 scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
        u32 ndtr = stm32_dma_read(dmadev, STM32_DMA_SNDTR(chan->id));
        u32 spar = stm32_dma_read(dmadev, STM32_DMA_SPAR(chan->id));
        u32 sm0ar = stm32_dma_read(dmadev, STM32_DMA_SM0AR(chan->id));
        u32 sm1ar = stm32_dma_read(dmadev, STM32_DMA_SM1AR(chan->id));
        u32 sfcr = stm32_dma_read(dmadev, STM32_DMA_SFCR(chan->id));

        dev_dbg(chan2dev(chan), "SCR:   0x%08x\n", scr);
        dev_dbg(chan2dev(chan), "NDTR:  0x%08x\n", ndtr);
        dev_dbg(chan2dev(chan), "SPAR:  0x%08x\n", spar);
        dev_dbg(chan2dev(chan), "SM0AR: 0x%08x\n", sm0ar);
        dev_dbg(chan2dev(chan), "SM1AR: 0x%08x\n", sm1ar);
        dev_dbg(chan2dev(chan), "SFCR:  0x%08x\n", sfcr);
}

static void stm32_dma_configure_next_sg(struct stm32_dma_chan *chan);

static void stm32_dma_start_transfer(struct stm32_dma_chan *chan)
{
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        struct virt_dma_desc *vdesc;
        struct stm32_dma_sg_req *sg_req;
        struct stm32_dma_chan_reg *reg;
        u32 status;
        int ret;

        ret = stm32_dma_disable_chan(chan);
        if (ret < 0)
                return;

        if (!chan->desc) {
                vdesc = vchan_next_desc(&chan->vchan);
                if (!vdesc)
                        return;

                chan->desc = to_stm32_dma_desc(vdesc);
                chan->next_sg = 0;
        }

        if (chan->next_sg == chan->desc->num_sgs)
                chan->next_sg = 0;

        sg_req = &chan->desc->sg_req[chan->next_sg];
        reg = &sg_req->chan_reg;

        stm32_dma_write(dmadev, STM32_DMA_SCR(chan->id), reg->dma_scr);
        stm32_dma_write(dmadev, STM32_DMA_SPAR(chan->id), reg->dma_spar);
        stm32_dma_write(dmadev, STM32_DMA_SM0AR(chan->id), reg->dma_sm0ar);
        stm32_dma_write(dmadev, STM32_DMA_SFCR(chan->id), reg->dma_sfcr);
        stm32_dma_write(dmadev, STM32_DMA_SM1AR(chan->id), reg->dma_sm1ar);
        stm32_dma_write(dmadev, STM32_DMA_SNDTR(chan->id), reg->dma_sndtr);

        chan->next_sg++;

        /* Clear interrupt status if it is there */
        status = stm32_dma_irq_status(chan);
        if (status)
                stm32_dma_irq_clear(chan, status);

        if (chan->desc->cyclic)
                stm32_dma_configure_next_sg(chan);

        stm32_dma_dump_reg(chan);

        /* Start DMA */
        reg->dma_scr |= STM32_DMA_SCR_EN;
        stm32_dma_write(dmadev, STM32_DMA_SCR(chan->id), reg->dma_scr);

        chan->busy = true;

        dev_dbg(chan2dev(chan), "vchan %pK: started\n", &chan->vchan);
}

static void stm32_dma_configure_next_sg(struct stm32_dma_chan *chan)
{
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        struct stm32_dma_sg_req *sg_req;
        u32 dma_scr, dma_sm0ar, dma_sm1ar, id;

        id = chan->id;
        dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));

        if (dma_scr & STM32_DMA_SCR_DBM) {
                if (chan->next_sg == chan->desc->num_sgs)
                        chan->next_sg = 0;

                sg_req = &chan->desc->sg_req[chan->next_sg];

                if (dma_scr & STM32_DMA_SCR_CT) {
                        dma_sm0ar = sg_req->chan_reg.dma_sm0ar;
                        stm32_dma_write(dmadev, STM32_DMA_SM0AR(id), dma_sm0ar);
                        dev_dbg(chan2dev(chan), "CT=1 <=> SM0AR: 0x%08x\n",
                                stm32_dma_read(dmadev, STM32_DMA_SM0AR(id)));
                } else {
                        dma_sm1ar = sg_req->chan_reg.dma_sm1ar;
                        stm32_dma_write(dmadev, STM32_DMA_SM1AR(id), dma_sm1ar);
                        dev_dbg(chan2dev(chan), "CT=0 <=> SM1AR: 0x%08x\n",
                                stm32_dma_read(dmadev, STM32_DMA_SM1AR(id)));
                }
        }
}

static void stm32_dma_handle_chan_done(struct stm32_dma_chan *chan)
{
        if (chan->desc) {
                if (chan->desc->cyclic) {
                        vchan_cyclic_callback(&chan->desc->vdesc);
                        chan->next_sg++;
                        stm32_dma_configure_next_sg(chan);
                } else {
                        chan->busy = false;
                        if (chan->next_sg == chan->desc->num_sgs) {
                                list_del(&chan->desc->vdesc.node);
                                vchan_cookie_complete(&chan->desc->vdesc);
                                chan->desc = NULL;
                        }
                        stm32_dma_start_transfer(chan);
                }
        }
}

static irqreturn_t stm32_dma_chan_irq(int irq, void *devid)
{
        struct stm32_dma_chan *chan = devid;
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        u32 status, scr, sfcr;

        spin_lock(&chan->vchan.lock);

        status = stm32_dma_irq_status(chan);
        scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
        sfcr = stm32_dma_read(dmadev, STM32_DMA_SFCR(chan->id));

        if (status & STM32_DMA_TCI) {
                stm32_dma_irq_clear(chan, STM32_DMA_TCI);
                if (scr & STM32_DMA_SCR_TCIE)
                        stm32_dma_handle_chan_done(chan);
                status &= ~STM32_DMA_TCI;
        }
        if (status & STM32_DMA_HTI) {
                stm32_dma_irq_clear(chan, STM32_DMA_HTI);
                status &= ~STM32_DMA_HTI;
        }
        if (status & STM32_DMA_FEI) {
                stm32_dma_irq_clear(chan, STM32_DMA_FEI);
                status &= ~STM32_DMA_FEI;
                if (sfcr & STM32_DMA_SFCR_FEIE) {
                        if (!(scr & STM32_DMA_SCR_EN))
                                dev_err(chan2dev(chan), "FIFO Error\n");
                        else
                                dev_dbg(chan2dev(chan), "FIFO over/underrun\n");
                }
        }
        if (status) {
                stm32_dma_irq_clear(chan, status);
                dev_err(chan2dev(chan), "DMA error: status=0x%08x\n", status);
                if (!(scr & STM32_DMA_SCR_EN))
                        dev_err(chan2dev(chan), "chan disabled by HW\n");
        }

        spin_unlock(&chan->vchan.lock);

        return IRQ_HANDLED;
}

static void stm32_dma_issue_pending(struct dma_chan *c)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        unsigned long flags;

        spin_lock_irqsave(&chan->vchan.lock, flags);
        if (vchan_issue_pending(&chan->vchan) && !chan->desc && !chan->busy) {
                dev_dbg(chan2dev(chan), "vchan %pK: issued\n", &chan->vchan);
                stm32_dma_start_transfer(chan);

        }
        spin_unlock_irqrestore(&chan->vchan.lock, flags);
}

static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
                                    enum dma_transfer_direction direction,
                                    enum dma_slave_buswidth *buswidth,
                                    u32 buf_len)
{
        enum dma_slave_buswidth src_addr_width, dst_addr_width;
        int src_bus_width, dst_bus_width;
        int src_burst_size, dst_burst_size;
        u32 src_maxburst, dst_maxburst, src_best_burst, dst_best_burst;
        u32 dma_scr, threshold;

        src_addr_width = chan->dma_sconfig.src_addr_width;
        dst_addr_width = chan->dma_sconfig.dst_addr_width;
        src_maxburst = chan->dma_sconfig.src_maxburst;
        dst_maxburst = chan->dma_sconfig.dst_maxburst;
        threshold = chan->threshold;

        switch (direction) {
        case DMA_MEM_TO_DEV:
                /* Set device data size */
                dst_bus_width = stm32_dma_get_width(chan, dst_addr_width);
                if (dst_bus_width < 0)
                        return dst_bus_width;

                /* Set device burst size */
                dst_best_burst = stm32_dma_get_best_burst(buf_len,
                                                          dst_maxburst,
                                                          threshold,
                                                          dst_addr_width);

                dst_burst_size = stm32_dma_get_burst(chan, dst_best_burst);
                if (dst_burst_size < 0)
                        return dst_burst_size;

                /* Set memory data size */
                src_addr_width = stm32_dma_get_max_width(buf_len, threshold);
                chan->mem_width = src_addr_width;
                src_bus_width = stm32_dma_get_width(chan, src_addr_width);
                if (src_bus_width < 0)
                        return src_bus_width;

                /* Set memory burst size */
                src_maxburst = STM32_DMA_MAX_BURST;
                src_best_burst = stm32_dma_get_best_burst(buf_len,
                                                          src_maxburst,
                                                          threshold,
                                                          src_addr_width);
                src_burst_size = stm32_dma_get_burst(chan, src_best_burst);
                if (src_burst_size < 0)
                        return src_burst_size;

                dma_scr = STM32_DMA_SCR_DIR(STM32_DMA_MEM_TO_DEV) |
                        STM32_DMA_SCR_PSIZE(dst_bus_width) |
                        STM32_DMA_SCR_MSIZE(src_bus_width) |
                        STM32_DMA_SCR_PBURST(dst_burst_size) |
                        STM32_DMA_SCR_MBURST(src_burst_size);

                /* Set FIFO threshold */
                chan->chan_reg.dma_sfcr &= ~STM32_DMA_SFCR_FTH_MASK;
                chan->chan_reg.dma_sfcr |= STM32_DMA_SFCR_FTH(threshold);

                /* Set peripheral address */
                chan->chan_reg.dma_spar = chan->dma_sconfig.dst_addr;
                *buswidth = dst_addr_width;
                break;

        case DMA_DEV_TO_MEM:
                /* Set device data size */
                src_bus_width = stm32_dma_get_width(chan, src_addr_width);
                if (src_bus_width < 0)
                        return src_bus_width;

                /* Set device burst size */
                src_best_burst = stm32_dma_get_best_burst(buf_len,
                                                          src_maxburst,
                                                          threshold,
                                                          src_addr_width);
                chan->mem_burst = src_best_burst;
                src_burst_size = stm32_dma_get_burst(chan, src_best_burst);
                if (src_burst_size < 0)
                        return src_burst_size;

                /* Set memory data size */
                dst_addr_width = stm32_dma_get_max_width(buf_len, threshold);
                chan->mem_width = dst_addr_width;
                dst_bus_width = stm32_dma_get_width(chan, dst_addr_width);
                if (dst_bus_width < 0)
                        return dst_bus_width;

                /* Set memory burst size */
                dst_maxburst = STM32_DMA_MAX_BURST;
                dst_best_burst = stm32_dma_get_best_burst(buf_len,
                                                          dst_maxburst,
                                                          threshold,
                                                          dst_addr_width);
                chan->mem_burst = dst_best_burst;
                dst_burst_size = stm32_dma_get_burst(chan, dst_best_burst);
                if (dst_burst_size < 0)
                        return dst_burst_size;

                dma_scr = STM32_DMA_SCR_DIR(STM32_DMA_DEV_TO_MEM) |
                        STM32_DMA_SCR_PSIZE(src_bus_width) |
                        STM32_DMA_SCR_MSIZE(dst_bus_width) |
                        STM32_DMA_SCR_PBURST(src_burst_size) |
                        STM32_DMA_SCR_MBURST(dst_burst_size);

                /* Set FIFO threshold */
                chan->chan_reg.dma_sfcr &= ~STM32_DMA_SFCR_FTH_MASK;
                chan->chan_reg.dma_sfcr |= STM32_DMA_SFCR_FTH(threshold);

                /* Set peripheral address */
                chan->chan_reg.dma_spar = chan->dma_sconfig.src_addr;
                *buswidth = chan->dma_sconfig.src_addr_width;
                break;

        default:
                dev_err(chan2dev(chan), "Dma direction is not supported\n");
                return -EINVAL;
        }

        stm32_dma_set_fifo_config(chan, src_best_burst, dst_best_burst);

        /* Set DMA control register */
        chan->chan_reg.dma_scr &= ~(STM32_DMA_SCR_DIR_MASK |
                        STM32_DMA_SCR_PSIZE_MASK | STM32_DMA_SCR_MSIZE_MASK |
                        STM32_DMA_SCR_PBURST_MASK | STM32_DMA_SCR_MBURST_MASK);
        chan->chan_reg.dma_scr |= dma_scr;

        return 0;
}

static void stm32_dma_clear_reg(struct stm32_dma_chan_reg *regs)
{
        memset(regs, 0, sizeof(struct stm32_dma_chan_reg));
}

static struct dma_async_tx_descriptor *stm32_dma_prep_slave_sg(
        struct dma_chan *c, struct scatterlist *sgl,
        u32 sg_len, enum dma_transfer_direction direction,
        unsigned long flags, void *context)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        struct stm32_dma_desc *desc;
        struct scatterlist *sg;
        enum dma_slave_buswidth buswidth;
        u32 nb_data_items;
        int i, ret;

        if (!chan->config_init) {
                dev_err(chan2dev(chan), "dma channel is not configured\n");
                return NULL;
        }

        if (sg_len < 1) {
                dev_err(chan2dev(chan), "Invalid segment length %d\n", sg_len);
                return NULL;
        }

        desc = stm32_dma_alloc_desc(sg_len);
        if (!desc)
                return NULL;

        /* Set peripheral flow controller */
        if (chan->dma_sconfig.device_fc)
                chan->chan_reg.dma_scr |= STM32_DMA_SCR_PFCTRL;
        else
                chan->chan_reg.dma_scr &= ~STM32_DMA_SCR_PFCTRL;

        for_each_sg(sgl, sg, sg_len, i) {
                ret = stm32_dma_set_xfer_param(chan, direction, &buswidth,
                                               sg_dma_len(sg));
                if (ret < 0)
                        goto err;

                desc->sg_req[i].len = sg_dma_len(sg);

                nb_data_items = desc->sg_req[i].len / buswidth;
                if (nb_data_items > STM32_DMA_ALIGNED_MAX_DATA_ITEMS) {
                        dev_err(chan2dev(chan), "nb items not supported\n");
                        goto err;
                }

                stm32_dma_clear_reg(&desc->sg_req[i].chan_reg);
                desc->sg_req[i].chan_reg.dma_scr = chan->chan_reg.dma_scr;
                desc->sg_req[i].chan_reg.dma_sfcr = chan->chan_reg.dma_sfcr;
                desc->sg_req[i].chan_reg.dma_spar = chan->chan_reg.dma_spar;
                desc->sg_req[i].chan_reg.dma_sm0ar = sg_dma_address(sg);
                desc->sg_req[i].chan_reg.dma_sm1ar = sg_dma_address(sg);
                desc->sg_req[i].chan_reg.dma_sndtr = nb_data_items;
        }

        desc->num_sgs = sg_len;
        desc->cyclic = false;

        return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);

err:
        kfree(desc);
        return NULL;
}

static struct dma_async_tx_descriptor *stm32_dma_prep_dma_cyclic(
        struct dma_chan *c, dma_addr_t buf_addr, size_t buf_len,
        size_t period_len, enum dma_transfer_direction direction,
        unsigned long flags)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        struct stm32_dma_desc *desc;
        enum dma_slave_buswidth buswidth;
        u32 num_periods, nb_data_items;
        int i, ret;

        if (!buf_len || !period_len) {
                dev_err(chan2dev(chan), "Invalid buffer/period len\n");
                return NULL;
        }

        if (!chan->config_init) {
                dev_err(chan2dev(chan), "dma channel is not configured\n");
                return NULL;
        }

        if (buf_len % period_len) {
                dev_err(chan2dev(chan), "buf_len not multiple of period_len\n");
                return NULL;
        }

        /*
         * We allow to take more number of requests till DMA is
         * not started. The driver will loop over all requests.
         * Once DMA is started then new requests can be queued only after
         * terminating the DMA.
         */
        if (chan->busy) {
                dev_err(chan2dev(chan), "Request not allowed when dma busy\n");
                return NULL;
        }

        ret = stm32_dma_set_xfer_param(chan, direction, &buswidth, period_len);
        if (ret < 0)
                return NULL;

        nb_data_items = period_len / buswidth;
        if (nb_data_items > STM32_DMA_ALIGNED_MAX_DATA_ITEMS) {
                dev_err(chan2dev(chan), "number of items not supported\n");
                return NULL;
        }

        /*  Enable Circular mode or double buffer mode */
        if (buf_len == period_len)
                chan->chan_reg.dma_scr |= STM32_DMA_SCR_CIRC;
        else
                chan->chan_reg.dma_scr |= STM32_DMA_SCR_DBM;

        /* Clear periph ctrl if client set it */
        chan->chan_reg.dma_scr &= ~STM32_DMA_SCR_PFCTRL;

        num_periods = buf_len / period_len;

        desc = stm32_dma_alloc_desc(num_periods);
        if (!desc)
                return NULL;

        for (i = 0; i < num_periods; i++) {
                desc->sg_req[i].len = period_len;

                stm32_dma_clear_reg(&desc->sg_req[i].chan_reg);
                desc->sg_req[i].chan_reg.dma_scr = chan->chan_reg.dma_scr;
                desc->sg_req[i].chan_reg.dma_sfcr = chan->chan_reg.dma_sfcr;
                desc->sg_req[i].chan_reg.dma_spar = chan->chan_reg.dma_spar;
                desc->sg_req[i].chan_reg.dma_sm0ar = buf_addr;
                desc->sg_req[i].chan_reg.dma_sm1ar = buf_addr;
                desc->sg_req[i].chan_reg.dma_sndtr = nb_data_items;
                buf_addr += period_len;
        }

        desc->num_sgs = num_periods;
        desc->cyclic = true;

        return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
}

static struct dma_async_tx_descriptor *stm32_dma_prep_dma_memcpy(
        struct dma_chan *c, dma_addr_t dest,
        dma_addr_t src, size_t len, unsigned long flags)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        enum dma_slave_buswidth max_width;
        struct stm32_dma_desc *desc;
        size_t xfer_count, offset;
        u32 num_sgs, best_burst, dma_burst, threshold;
        int i;

        num_sgs = DIV_ROUND_UP(len, STM32_DMA_ALIGNED_MAX_DATA_ITEMS);
        desc = stm32_dma_alloc_desc(num_sgs);
        if (!desc)
                return NULL;

        threshold = chan->threshold;

        for (offset = 0, i = 0; offset < len; offset += xfer_count, i++) {
                xfer_count = min_t(size_t, len - offset,
                                   STM32_DMA_ALIGNED_MAX_DATA_ITEMS);

                /* Compute best burst size */
                max_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
                best_burst = stm32_dma_get_best_burst(len, STM32_DMA_MAX_BURST,
                                                      threshold, max_width);
                dma_burst = stm32_dma_get_burst(chan, best_burst);

                stm32_dma_clear_reg(&desc->sg_req[i].chan_reg);
                desc->sg_req[i].chan_reg.dma_scr =
                        STM32_DMA_SCR_DIR(STM32_DMA_MEM_TO_MEM) |
                        STM32_DMA_SCR_PBURST(dma_burst) |
                        STM32_DMA_SCR_MBURST(dma_burst) |
                        STM32_DMA_SCR_MINC |
                        STM32_DMA_SCR_PINC |
                        STM32_DMA_SCR_TCIE |
                        STM32_DMA_SCR_TEIE;
                desc->sg_req[i].chan_reg.dma_sfcr |= STM32_DMA_SFCR_MASK;
                desc->sg_req[i].chan_reg.dma_sfcr |=
                        STM32_DMA_SFCR_FTH(threshold);
                desc->sg_req[i].chan_reg.dma_spar = src + offset;
                desc->sg_req[i].chan_reg.dma_sm0ar = dest + offset;
                desc->sg_req[i].chan_reg.dma_sndtr = xfer_count;
                desc->sg_req[i].len = xfer_count;
        }

        desc->num_sgs = num_sgs;
        desc->cyclic = false;

        return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
}

static u32 stm32_dma_get_remaining_bytes(struct stm32_dma_chan *chan)
{
        u32 dma_scr, width, ndtr;
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);

        dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
        width = STM32_DMA_SCR_PSIZE_GET(dma_scr);
        ndtr = stm32_dma_read(dmadev, STM32_DMA_SNDTR(chan->id));

        return ndtr << width;
}

/**
 * stm32_dma_is_current_sg - check that expected sg_req is currently transferred
 * @chan: dma channel
 *
 * This function called when IRQ are disable, checks that the hardware has not
 * switched on the next transfer in double buffer mode. The test is done by
 * comparing the next_sg memory address with the hardware related register
 * (based on CT bit value).
 *
 * Returns true if expected current transfer is still running or double
 * buffer mode is not activated.
 */
static bool stm32_dma_is_current_sg(struct stm32_dma_chan *chan)
{
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        struct stm32_dma_sg_req *sg_req;
        u32 dma_scr, dma_smar, id;

        id = chan->id;
        dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));

        if (!(dma_scr & STM32_DMA_SCR_DBM))
                return true;

        sg_req = &chan->desc->sg_req[chan->next_sg];

        if (dma_scr & STM32_DMA_SCR_CT) {
                dma_smar = stm32_dma_read(dmadev, STM32_DMA_SM0AR(id));
                return (dma_smar == sg_req->chan_reg.dma_sm0ar);
        }

        dma_smar = stm32_dma_read(dmadev, STM32_DMA_SM1AR(id));

        return (dma_smar == sg_req->chan_reg.dma_sm1ar);
}

static size_t stm32_dma_desc_residue(struct stm32_dma_chan *chan,
                                     struct stm32_dma_desc *desc,
                                     u32 next_sg)
{
        u32 modulo, burst_size;
        u32 residue;
        u32 n_sg = next_sg;
        struct stm32_dma_sg_req *sg_req = &chan->desc->sg_req[chan->next_sg];
        int i;

        /*
         * Calculate the residue means compute the descriptors
         * information:
         * - the sg_req currently transferred
         * - the Hardware remaining position in this sg (NDTR bits field).
         *
         * A race condition may occur if DMA is running in cyclic or double
         * buffer mode, since the DMA register are automatically reloaded at end
         * of period transfer. The hardware may have switched to the next
         * transfer (CT bit updated) just before the position (SxNDTR reg) is
         * read.
         * In this case the SxNDTR reg could (or not) correspond to the new
         * transfer position, and not the expected one.
         * The strategy implemented in the stm32 driver is to:
         *  - read the SxNDTR register
         *  - crosscheck that hardware is still in current transfer.
         * In case of switch, we can assume that the DMA is at the beginning of
         * the next transfer. So we approximate the residue in consequence, by
         * pointing on the beginning of next transfer.
         *
         * This race condition doesn't apply for none cyclic mode, as double
         * buffer is not used. In such situation registers are updated by the
         * software.
         */

        residue = stm32_dma_get_remaining_bytes(chan);

        if (!stm32_dma_is_current_sg(chan)) {
                n_sg++;
                if (n_sg == chan->desc->num_sgs)
                        n_sg = 0;
                residue = sg_req->len;
        }

        /*
         * In cyclic mode, for the last period, residue = remaining bytes
         * from NDTR,
         * else for all other periods in cyclic mode, and in sg mode,
         * residue = remaining bytes from NDTR + remaining
         * periods/sg to be transferred
         */
        if (!chan->desc->cyclic || n_sg != 0)
                for (i = n_sg; i < desc->num_sgs; i++)
                        residue += desc->sg_req[i].len;

        if (!chan->mem_burst)
                return residue;

        burst_size = chan->mem_burst * chan->mem_width;
        modulo = residue % burst_size;
        if (modulo)
                residue = residue - modulo + burst_size;

        return residue;
}

static enum dma_status stm32_dma_tx_status(struct dma_chan *c,
                                           dma_cookie_t cookie,
                                           struct dma_tx_state *state)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        struct virt_dma_desc *vdesc;
        enum dma_status status;
        unsigned long flags;
        u32 residue = 0;

        status = dma_cookie_status(c, cookie, state);
        if (status == DMA_COMPLETE || !state)
                return status;

        spin_lock_irqsave(&chan->vchan.lock, flags);
        vdesc = vchan_find_desc(&chan->vchan, cookie);
        if (chan->desc && cookie == chan->desc->vdesc.tx.cookie)
                residue = stm32_dma_desc_residue(chan, chan->desc,
                                                 chan->next_sg);
        else if (vdesc)
                residue = stm32_dma_desc_residue(chan,
                                                 to_stm32_dma_desc(vdesc), 0);
        dma_set_residue(state, residue);

        spin_unlock_irqrestore(&chan->vchan.lock, flags);

        return status;
}

static int stm32_dma_alloc_chan_resources(struct dma_chan *c)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        int ret;

        chan->config_init = false;

        ret = pm_runtime_get_sync(dmadev->ddev.dev);
        if (ret < 0)
                return ret;

        ret = stm32_dma_disable_chan(chan);
        if (ret < 0)
                pm_runtime_put(dmadev->ddev.dev);

        return ret;
}

static void stm32_dma_free_chan_resources(struct dma_chan *c)
{
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        unsigned long flags;

        dev_dbg(chan2dev(chan), "Freeing channel %d\n", chan->id);

        if (chan->busy) {
                spin_lock_irqsave(&chan->vchan.lock, flags);
                stm32_dma_stop(chan);
                chan->desc = NULL;
                spin_unlock_irqrestore(&chan->vchan.lock, flags);
        }

        pm_runtime_put(dmadev->ddev.dev);

        vchan_free_chan_resources(to_virt_chan(c));
}

static void stm32_dma_desc_free(struct virt_dma_desc *vdesc)
{
        kfree(container_of(vdesc, struct stm32_dma_desc, vdesc));
}

static void stm32_dma_set_config(struct stm32_dma_chan *chan,
                                 struct stm32_dma_cfg *cfg)
{
        stm32_dma_clear_reg(&chan->chan_reg);

        chan->chan_reg.dma_scr = cfg->stream_config & STM32_DMA_SCR_CFG_MASK;
        chan->chan_reg.dma_scr |= STM32_DMA_SCR_REQ(cfg->request_line);

        /* Enable Interrupts  */
        chan->chan_reg.dma_scr |= STM32_DMA_SCR_TEIE | STM32_DMA_SCR_TCIE;

        chan->threshold = STM32_DMA_THRESHOLD_FTR_GET(cfg->features);
}

static struct dma_chan *stm32_dma_of_xlate(struct of_phandle_args *dma_spec,
                                           struct of_dma *ofdma)
{
        struct stm32_dma_device *dmadev = ofdma->of_dma_data;
        struct device *dev = dmadev->ddev.dev;
        struct stm32_dma_cfg cfg;
        struct stm32_dma_chan *chan;
        struct dma_chan *c;

        if (dma_spec->args_count < 4) {
                dev_err(dev, "Bad number of cells\n");
                return NULL;
        }

        cfg.channel_id = dma_spec->args[0];
        cfg.request_line = dma_spec->args[1];
        cfg.stream_config = dma_spec->args[2];
        cfg.features = dma_spec->args[3];

        if (cfg.channel_id >= STM32_DMA_MAX_CHANNELS ||
            cfg.request_line >= STM32_DMA_MAX_REQUEST_ID) {
                dev_err(dev, "Bad channel and/or request id\n");
                return NULL;
        }

        chan = &dmadev->chan[cfg.channel_id];

        c = dma_get_slave_channel(&chan->vchan.chan);
        if (!c) {
                dev_err(dev, "No more channels available\n");
                return NULL;
        }

        stm32_dma_set_config(chan, &cfg);

        return c;
}

static const struct of_device_id stm32_dma_of_match[] = {
        { .compatible = "st,stm32-dma", },
        { /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, stm32_dma_of_match);

static int stm32_dma_probe(struct platform_device *pdev)
{
        struct stm32_dma_chan *chan;
        struct stm32_dma_device *dmadev;
        struct dma_device *dd;
        const struct of_device_id *match;
        struct resource *res;
        int i, ret;

        match = of_match_device(stm32_dma_of_match, &pdev->dev);
        if (!match) {
                dev_err(&pdev->dev, "Error: No device match found\n");
                return -ENODEV;
        }

        dmadev = devm_kzalloc(&pdev->dev, sizeof(*dmadev), GFP_KERNEL);
        if (!dmadev)
                return -ENOMEM;

        dd = &dmadev->ddev;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        dmadev->base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(dmadev->base))
                return PTR_ERR(dmadev->base);

        dmadev->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(dmadev->clk)) {
                dev_err(&pdev->dev, "Error: Missing controller clock\n");
                return PTR_ERR(dmadev->clk);
        }

        ret = clk_prepare_enable(dmadev->clk);
        if (ret < 0) {
                dev_err(&pdev->dev, "clk_prep_enable error: %d\n", ret);
                return ret;
        }

        dmadev->mem2mem = of_property_read_bool(pdev->dev.of_node,
                                                "st,mem2mem");

        dmadev->rst = devm_reset_control_get(&pdev->dev, NULL);
        if (!IS_ERR(dmadev->rst)) {
                reset_control_assert(dmadev->rst);
                udelay(2);
                reset_control_deassert(dmadev->rst);
        }

        dma_cap_set(DMA_SLAVE, dd->cap_mask);
        dma_cap_set(DMA_PRIVATE, dd->cap_mask);
        dma_cap_set(DMA_CYCLIC, dd->cap_mask);
        dd->device_alloc_chan_resources = stm32_dma_alloc_chan_resources;
        dd->device_free_chan_resources = stm32_dma_free_chan_resources;
        dd->device_tx_status = stm32_dma_tx_status;
        dd->device_issue_pending = stm32_dma_issue_pending;
        dd->device_prep_slave_sg = stm32_dma_prep_slave_sg;
        dd->device_prep_dma_cyclic = stm32_dma_prep_dma_cyclic;
        dd->device_config = stm32_dma_slave_config;
        dd->device_terminate_all = stm32_dma_terminate_all;
        dd->device_synchronize = stm32_dma_synchronize;
        dd->src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
                BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
                BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
        dd->dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
                BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
                BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
        dd->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
        dd->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
        dd->max_burst = STM32_DMA_MAX_BURST;
        dd->dev = &pdev->dev;
        INIT_LIST_HEAD(&dd->channels);

        if (dmadev->mem2mem) {
                dma_cap_set(DMA_MEMCPY, dd->cap_mask);
                dd->device_prep_dma_memcpy = stm32_dma_prep_dma_memcpy;
                dd->directions |= BIT(DMA_MEM_TO_MEM);
        }

        for (i = 0; i < STM32_DMA_MAX_CHANNELS; i++) {
                chan = &dmadev->chan[i];
                chan->id = i;
                chan->vchan.desc_free = stm32_dma_desc_free;
                vchan_init(&chan->vchan, dd);
        }

        ret = dma_async_device_register(dd);
        if (ret)
                goto clk_free;

        for (i = 0; i < STM32_DMA_MAX_CHANNELS; i++) {
                chan = &dmadev->chan[i];
                ret = platform_get_irq(pdev, i);
                if (ret < 0)  {
                        if (ret != -EPROBE_DEFER)
                                dev_err(&pdev->dev,
                                        "No irq resource for chan %d\n", i);
                        goto err_unregister;
                }
                chan->irq = ret;

                ret = devm_request_irq(&pdev->dev, chan->irq,
                                       stm32_dma_chan_irq, 0,
                                       dev_name(chan2dev(chan)), chan);
                if (ret) {
                        dev_err(&pdev->dev,
                                "request_irq failed with err %d channel %d\n",
                                ret, i);
                        goto err_unregister;
                }
        }

        ret = of_dma_controller_register(pdev->dev.of_node,
                                         stm32_dma_of_xlate, dmadev);
        if (ret < 0) {
                dev_err(&pdev->dev,
                        "STM32 DMA DMA OF registration failed %d\n", ret);
                goto err_unregister;
        }

        platform_set_drvdata(pdev, dmadev);

        pm_runtime_set_active(&pdev->dev);
        pm_runtime_enable(&pdev->dev);
        pm_runtime_get_noresume(&pdev->dev);
        pm_runtime_put(&pdev->dev);

        dev_info(&pdev->dev, "STM32 DMA driver registered\n");

        return 0;

err_unregister:
        dma_async_device_unregister(dd);
clk_free:
        clk_disable_unprepare(dmadev->clk);

        return ret;
}

#ifdef CONFIG_PM
static int stm32_dma_runtime_suspend(struct device *dev)
{
        struct stm32_dma_device *dmadev = dev_get_drvdata(dev);

        clk_disable_unprepare(dmadev->clk);

        return 0;
}

static int stm32_dma_runtime_resume(struct device *dev)
{
        struct stm32_dma_device *dmadev = dev_get_drvdata(dev);
        int ret;

        ret = clk_prepare_enable(dmadev->clk);
        if (ret) {
                dev_err(dev, "failed to prepare_enable clock\n");
                return ret;
        }

        return 0;
}
#endif

static const struct dev_pm_ops stm32_dma_pm_ops = {
        SET_RUNTIME_PM_OPS(stm32_dma_runtime_suspend,
                           stm32_dma_runtime_resume, NULL)
};

static struct platform_driver stm32_dma_driver = {
        .driver = {
                .name = "stm32-dma",
                .of_match_table = stm32_dma_of_match,
                .pm = &stm32_dma_pm_ops,
        },
};

static int __init stm32_dma_init(void)
{
        return platform_driver_probe(&stm32_dma_driver, stm32_dma_probe);
}
subsys_initcall(stm32_dma_init);