// SPDX-License-Identifier: GPL-2.0-only
/*
 * Novatek NT35510 panel driver
 * Copyright (C) 2020 Linus Walleij <linus.walleij@linaro.org>
 * Based on code by Robert Teather (C) 2012 Samsung
 *
 * This display driver (and I refer to the physical component NT35510,
 * not this Linux kernel software driver) can handle:
 * 480x864, 480x854, 480x800, 480x720 and 480x640 pixel displays.
 * It has 480x840x24bit SRAM embedded for storing a frame.
 * When powered on the display is by default in 480x800 mode.
 *
 * The actual panels using this component have different names, but
 * the code needed to set up and configure the panel will be similar,
 * so they should all use the NT35510 driver with appropriate configuration
 * per-panel, e.g. for physical size.
 *
 * This driver is for the DSI interface to panels using the NT35510.
 *
 * The NT35510 can also use an RGB (DPI) interface combined with an
 * I2C or SPI interface for setting up the NT35510. If this is needed
 * this panel driver should be refactored to also support that use
 * case.
 */
#include <linux/backlight.h>
#include <linux/bitops.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>

#include <video/mipi_display.h>

#include <drm/drm_mipi_dsi.h>
#include <drm/drm_modes.h>
#include <drm/drm_panel.h>

#define MCS_CMD_MAUCCTR         0xF0 /* Manufacturer command enable */
#define MCS_CMD_READ_ID1        0xDA
#define MCS_CMD_READ_ID2        0xDB
#define MCS_CMD_READ_ID3        0xDC
#define MCS_CMD_MTP_READ_SETTING 0xF8 /* Uncertain about name */
#define MCS_CMD_MTP_READ_PARAM 0xFF /* Uncertain about name */

/*
 * These manufacturer commands are available after we enable manufacturer
 * command set (MCS) for page 0.
 */
#define NT35510_P0_DOPCTR 0xB1
#define NT35510_P0_SDHDTCTR 0xB6
#define NT35510_P0_GSEQCTR 0xB7
#define NT35510_P0_SDEQCTR 0xB8
#define NT35510_P0_SDVPCTR 0xBA
#define NT35510_P0_DPFRCTR1 0xBD
#define NT35510_P0_DPFRCTR2 0xBE
#define NT35510_P0_DPFRCTR3 0xBF
#define NT35510_P0_DPMCTR12 0xCC

#define NT35510_P0_DOPCTR_LEN 2
#define NT35510_P0_GSEQCTR_LEN 2
#define NT35510_P0_SDEQCTR_LEN 4
#define NT35510_P0_SDVPCTR_LEN 1
#define NT35510_P0_DPFRCTR1_LEN 5
#define NT35510_P0_DPFRCTR2_LEN 5
#define NT35510_P0_DPFRCTR3_LEN 5
#define NT35510_P0_DPMCTR12_LEN 3

#define NT35510_DOPCTR_0_RAMKP BIT(7) /* Contents kept in sleep */
#define NT35510_DOPCTR_0_DSITE BIT(6) /* Enable TE signal */
#define NT35510_DOPCTR_0_DSIG BIT(5) /* Enable generic read/write */
#define NT35510_DOPCTR_0_DSIM BIT(4) /* Enable video mode on DSI */
#define NT35510_DOPCTR_0_EOTP BIT(3) /* Support EoTP */
#define NT35510_DOPCTR_0_N565 BIT(2) /* RGB or BGR pixel format */
#define NT35510_DOPCTR_1_TW_PWR_SEL BIT(4) /* TE power selector */
#define NT35510_DOPCTR_1_CRGB BIT(3) /* RGB or BGR byte order */
#define NT35510_DOPCTR_1_CTB BIT(2) /* Vertical scanning direction */
#define NT35510_DOPCTR_1_CRL BIT(1) /* Source driver data shift */
#define NT35510_P0_SDVPCTR_PRG BIT(2) /* 0 = normal operation, 1 = VGLO */
#define NT35510_P0_SDVPCTR_AVDD 0 /* source driver output = AVDD */
#define NT35510_P0_SDVPCTR_OFFCOL 1 /* source driver output = off color */
#define NT35510_P0_SDVPCTR_AVSS 2 /* source driver output = AVSS */
#define NT35510_P0_SDVPCTR_HI_Z 3 /* source driver output = High impedance */

/*
 * These manufacturer commands are available after we enable manufacturer
 * command set (MCS) for page 1.
 */
#define NT35510_P1_SETAVDD 0xB0
#define NT35510_P1_SETAVEE 0xB1
#define NT35510_P1_SETVCL 0xB2
#define NT35510_P1_SETVGH 0xB3
#define NT35510_P1_SETVRGH 0xB4
#define NT35510_P1_SETVGL 0xB5
#define NT35510_P1_BT1CTR 0xB6
#define NT35510_P1_BT2CTR 0xB7
#define NT35510_P1_BT3CTR 0xB8
#define NT35510_P1_BT4CTR 0xB9 /* VGH boosting times/freq */
#define NT35510_P1_BT5CTR 0xBA
#define NT35510_P1_PFMCTR 0xBB
#define NT35510_P1_SETVGP 0xBC
#define NT35510_P1_SETVGN 0xBD
#define NT35510_P1_SETVCMOFF 0xBE
#define NT35510_P1_VGHCTR 0xBF /* VGH output ctrl */
#define NT35510_P1_SET_GAMMA_RED_POS 0xD1
#define NT35510_P1_SET_GAMMA_GREEN_POS 0xD2
#define NT35510_P1_SET_GAMMA_BLUE_POS 0xD3
#define NT35510_P1_SET_GAMMA_RED_NEG 0xD4
#define NT35510_P1_SET_GAMMA_GREEN_NEG 0xD5
#define NT35510_P1_SET_GAMMA_BLUE_NEG 0xD6

/* AVDD and AVEE setting 3 bytes */
#define NT35510_P1_AVDD_LEN 3
#define NT35510_P1_AVEE_LEN 3
#define NT35510_P1_VGH_LEN 3
#define NT35510_P1_VGL_LEN 3
#define NT35510_P1_VGP_LEN 3
#define NT35510_P1_VGN_LEN 3
/* BT1CTR thru BT5CTR setting 3 bytes */
#define NT35510_P1_BT1CTR_LEN 3
#define NT35510_P1_BT2CTR_LEN 3
#define NT35510_P1_BT4CTR_LEN 3
#define NT35510_P1_BT5CTR_LEN 3
/* 52 gamma parameters times two per color: positive and negative */
#define NT35510_P1_GAMMA_LEN 52

/**
 * struct nt35510_config - the display-specific NT35510 configuration
 *
 * Some of the settings provide an array of bytes, A, B C which mean:
 * A = normal / idle off mode
 * B = idle on mode
 * C = partial / idle off mode
 *
 * Gamma correction arrays are 10bit numbers, two consecutive bytes
 * makes out one point on the gamma correction curve. The points are
 * not linearly placed along the X axis, we get points 0, 1, 3, 5
 * 7, 11, 15, 23, 31, 47, 63, 95, 127, 128, 160, 192, 208, 224, 232,
 * 240, 244, 248, 250, 252, 254, 255. The voltages tuples form
 * V0, V1, V3 ... V255, with 0x0000 being the lowest voltage and
 * 0x03FF being the highest voltage.
 *
 * Each value must be strictly higher than the previous value forming
 * a rising curve like this:
 *
 * ^
 * |                                        V255
 * |                                 V254
 * |                         ....
 * |                    V5
 * |           V3
 * |     V1
 * | V0
 * +------------------------------------------->
 *
 * The details about all settings can be found in the NT35510 Application
 * Note.
 */
struct nt35510_config {
        /**
         * @width_mm: physical panel width [mm]
         */
        u32 width_mm;
        /**
         * @height_mm: physical panel height [mm]
         */
        u32 height_mm;
        /**
         * @mode: the display mode. This is only relevant outside the panel
         * in video mode: in command mode this is configuring the internal
         * timing in the display controller.
         */
        const struct drm_display_mode mode;
        /**
         * @avdd: setting for AVDD ranging from 0x00 = 6.5V to 0x14 = 4.5V
         * in 0.1V steps the default is 0x05 which means 6.0V
         */
        u8 avdd[NT35510_P1_AVDD_LEN];
        /**
         * @bt1ctr: setting for boost power control for the AVDD step-up
         * circuit (1)
         * bits 0..2 in the lower nibble controls PCK, the booster clock
         * frequency for the step-up circuit:
         * 0 = Hsync/32
         * 1 = Hsync/16
         * 2 = Hsync/8
         * 3 = Hsync/4
         * 4 = Hsync/2
         * 5 = Hsync
         * 6 = Hsync x 2
         * 7 = Hsync x 4
         * bits 4..6 in the upper nibble controls BTP, the boosting
         * amplification for the the step-up circuit:
         * 0 = Disable
         * 1 = 1.5 x VDDB
         * 2 = 1.66 x VDDB
         * 3 = 2 x VDDB
         * 4 = 2.5 x VDDB
         * 5 = 3 x VDDB
         * The defaults are 4 and 4 yielding 0x44
         */
        u8 bt1ctr[NT35510_P1_BT1CTR_LEN];
        /**
         * @avee: setting for AVEE ranging from 0x00 = -6.5V to 0x14 = -4.5V
         * in 0.1V steps the default is 0x05 which means -6.0V
         */
        u8 avee[NT35510_P1_AVEE_LEN];
        /**
         * @bt2ctr: setting for boost power control for the AVEE step-up
         * circuit (2)
         * bits 0..2 in the lower nibble controls NCK, the booster clock
         * frequency, the values are the same as for PCK in @bt1ctr.
         * bits 4..5 in the upper nibble controls BTN, the boosting
         * amplification for the the step-up circuit.
         * 0 = Disable
         * 1 = -1.5 x VDDB
         * 2 = -2 x VDDB
         * 3 = -2.5 x VDDB
         * 4 = -3 x VDDB
         * The defaults are 4 and 3 yielding 0x34
         */
        u8 bt2ctr[NT35510_P1_BT2CTR_LEN];
        /**
         * @vgh: setting for VGH ranging from 0x00 = 7.0V to 0x0B = 18.0V
         * in 1V steps, the default is 0x08 which means 15V
         */
        u8 vgh[NT35510_P1_VGH_LEN];
        /**
         * @bt4ctr: setting for boost power control for the VGH step-up
         * circuit (4)
         * bits 0..2 in the lower nibble controls HCK, the booster clock
         * frequency, the values are the same as for PCK in @bt1ctr.
         * bits 4..5 in the upper nibble controls BTH, the boosting
         * amplification for the the step-up circuit.
         * 0 = AVDD + VDDB
         * 1 = AVDD - AVEE
         * 2 = AVDD - AVEE + VDDB
         * 3 = AVDD x 2 - AVEE
         * The defaults are 4 and 3 yielding 0x34
         */
        u8 bt4ctr[NT35510_P1_BT4CTR_LEN];
        /**
         * @vgl: setting for VGL ranging from 0x00 = -2V to 0x0f = -15V in
         * 1V steps, the default is 0x08 which means -10V
         */
        u8 vgl[NT35510_P1_VGL_LEN];
        /**
         * @bt5ctr: setting for boost power control for the VGL step-up
         * circuit (5)
         * bits 0..2 in the lower nibble controls LCK, the booster clock
         * frequency, the values are the same as for PCK in @bt1ctr.
         * bits 4..5 in the upper nibble controls BTL, the boosting
         * amplification for the the step-up circuit.
         * 0 = AVEE + VCL
         * 1 = AVEE - AVDD
         * 2 = AVEE + VCL - AVDD
         * 3 = AVEE x 2 - AVDD
         * The defaults are 3 and 2 yielding 0x32
         */
        u8 bt5ctr[NT35510_P1_BT5CTR_LEN];
        /**
         * @vgp: setting for VGP, the positive gamma divider voltages
         * VGMP the high voltage and VGSP the low voltage.
         * The first byte contains bit 8 of VGMP and VGSP in bits 4 and 0
         * The second byte contains bit 0..7 of VGMP
         * The third byte contains bit 0..7 of VGSP
         * VGMP 0x00 = 3.0V .. 0x108 = 6.3V in steps of 12.5mV
         * VGSP 0x00 = 0V .. 0x111 = 3.7V in steps of 12.5mV
         */
        u8 vgp[NT35510_P1_VGP_LEN];
        /**
         * @vgn: setting for VGN, the negative gamma divider voltages,
         * same layout of bytes as @vgp.
         */
        u8 vgn[NT35510_P1_VGN_LEN];
        /**
         * @sdeqctr: Source driver control settings, first byte is
         * 0 for mode 1 and 1 for mode 2. Mode 1 uses two steps and
         * mode 2 uses three steps meaning EQS3 is not used in mode
         * 1. Mode 2 is default. The last three parameters are EQS1, EQS2
         * and EQS3, setting the rise time for each equalizer step:
         * 0x00 = 0.0 us to 0x0f = 7.5 us in steps of 0.5us. The default
         * is 0x07 = 3.5 us.
         */
        u8 sdeqctr[NT35510_P0_SDEQCTR_LEN];
        /**
         * @sdvpctr: power/voltage behaviour during vertical porch time
         */
        u8 sdvpctr;
        /**
         * @t1: the number of pixel clocks on one scanline, range
         * 0x100 (258 ticks) .. 0x3FF (1024 ticks) so the value + 1
         * clock ticks.
         */
        u16 t1;
        /**
         * @vbp: vertical back porch toward the PANEL note: not toward
         * the DSI host; these are separate interfaces, in from DSI host
         * and out to the panel.
         */
        u8 vbp;
        /**
         * @vfp: vertical front porch toward the PANEL.
         */
        u8 vfp;
        /**
         * @psel: pixel clock divisor: 0 = 1, 1 = 2, 2 = 4, 3 = 8.
         */
        u8 psel;
        /**
         * @dpmctr12: Display timing control 12
         * Byte 1 bit 4 selects LVGL voltage level: 0 = VGLX, 1 = VGL_REG
         * Byte 1 bit 1 selects gate signal mode: 0 = non-overlap, 1 = overlap
         * Byte 1 bit 0 selects output signal control R/L swap, 0 = normal
         * 1 = swap all O->E, L->R
         * Byte 2 is CLW delay clock for CK O/E and CKB O/E signals:
         * 0x00 = 0us .. 0xFF = 12.75us in 0.05us steps
         * Byte 3 is FTI_H0 delay time for STP O/E signals:
         * 0x00 = 0us .. 0xFF = 12.75us in 0.05us steps
         */
        u8 dpmctr12[NT35510_P0_DPMCTR12_LEN];
        /**
         * @gamma_corr_pos_r: Red gamma correction parameters, positive
         */
        u8 gamma_corr_pos_r[NT35510_P1_GAMMA_LEN];
        /**
         * @gamma_corr_pos_g: Green gamma correction parameters, positive
         */
        u8 gamma_corr_pos_g[NT35510_P1_GAMMA_LEN];
        /**
         * @gamma_corr_pos_b: Blue gamma correction parameters, positive
         */
        u8 gamma_corr_pos_b[NT35510_P1_GAMMA_LEN];
        /**
         * @gamma_corr_neg_r: Red gamma correction parameters, negative
         */
        u8 gamma_corr_neg_r[NT35510_P1_GAMMA_LEN];
        /**
         * @gamma_corr_neg_g: Green gamma correction parameters, negative
         */
        u8 gamma_corr_neg_g[NT35510_P1_GAMMA_LEN];
        /**
         * @gamma_corr_neg_b: Blue gamma correction parameters, negative
         */
        u8 gamma_corr_neg_b[NT35510_P1_GAMMA_LEN];
};

/**
 * struct nt35510 - state container for the NT35510 panel
 */
struct nt35510 {
        /**
         * @dev: the container device
         */
        struct device *dev;
        /**
         * @conf: the specific panel configuration, as the NT35510
         * can be combined with many physical panels, they can have
         * different physical dimensions and gamma correction etc,
         * so this is stored in the config.
         */
        const struct nt35510_config *conf;
        /**
         * @panel: the DRM panel object for the instance
         */
        struct drm_panel panel;
        /**
         * @supplies: regulators supplying the panel
         */
        struct regulator_bulk_data supplies[2];
        /**
         * @reset_gpio: the reset line
         */
        struct gpio_desc *reset_gpio;
};

/* Manufacturer command has strictly this byte sequence */
static const u8 nt35510_mauc_mtp_read_param[] = { 0xAA, 0x55, 0x25, 0x01 };
static const u8 nt35510_mauc_mtp_read_setting[] = { 0x01, 0x02, 0x00, 0x20,
                                                    0x33, 0x13, 0x00, 0x40,
                                                    0x00, 0x00, 0x23, 0x02 };
static const u8 nt35510_mauc_select_page_0[] = { 0x55, 0xAA, 0x52, 0x08, 0x00 };
static const u8 nt35510_mauc_select_page_1[] = { 0x55, 0xAA, 0x52, 0x08, 0x01 };
static const u8 nt35510_vgh_on[] = { 0x01 };

static inline struct nt35510 *panel_to_nt35510(struct drm_panel *panel)
{
        return container_of(panel, struct nt35510, panel);
}

#define NT35510_ROTATE_0_SETTING        0x02
#define NT35510_ROTATE_180_SETTING      0x00

static int nt35510_send_long(struct nt35510 *nt, struct mipi_dsi_device *dsi,
                             u8 cmd, u8 cmdlen, const u8 *seq)
{
        const u8 *seqp = seq;
        int cmdwritten = 0;
        int chunk = cmdlen;
        int ret;

        if (chunk > 15)
                chunk = 15;
        ret = mipi_dsi_dcs_write(dsi, cmd, seqp, chunk);
        if (ret < 0) {
                dev_err(nt->dev, "error sending DCS command seq cmd %02x\n", cmd);
                return ret;
        }
        cmdwritten += chunk;
        seqp += chunk;

        while (cmdwritten < cmdlen) {
                chunk = cmdlen - cmdwritten;
                if (chunk > 15)
                        chunk = 15;
                ret = mipi_dsi_generic_write(dsi, seqp, chunk);
                if (ret < 0) {
                        dev_err(nt->dev, "error sending generic write seq %02x\n", cmd);
                        return ret;
                }
                cmdwritten += chunk;
                seqp += chunk;
        }
        dev_dbg(nt->dev, "sent command %02x %02x bytes\n", cmd, cmdlen);
        return 0;
}

static int nt35510_read_id(struct nt35510 *nt)
{
        struct mipi_dsi_device *dsi = to_mipi_dsi_device(nt->dev);
        u8 id1, id2, id3;
        int ret;

        ret = mipi_dsi_dcs_read(dsi, MCS_CMD_READ_ID1, &id1, 1);
        if (ret < 0) {
                dev_err(nt->dev, "could not read MTP ID1\n");
                return ret;
        }
        ret = mipi_dsi_dcs_read(dsi, MCS_CMD_READ_ID2, &id2, 1);
        if (ret < 0) {
                dev_err(nt->dev, "could not read MTP ID2\n");
                return ret;
        }
        ret = mipi_dsi_dcs_read(dsi, MCS_CMD_READ_ID3, &id3, 1);
        if (ret < 0) {
                dev_err(nt->dev, "could not read MTP ID3\n");
                return ret;
        }

        /*
         * Multi-Time Programmable (?) memory contains manufacturer
         * ID (e.g. Hydis 0x55), driver ID (e.g. NT35510 0xc0) and
         * version.
         */
        dev_info(nt->dev, "MTP ID manufacturer: %02x version: %02x driver: %02x\n", id1, id2, id3);

        return 0;
}

/**
 * nt35510_setup_power() - set up power config in page 1
 * @nt: the display instance to set up
 */
static int nt35510_setup_power(struct nt35510 *nt)
{
        struct mipi_dsi_device *dsi = to_mipi_dsi_device(nt->dev);
        int ret;

        ret = nt35510_send_long(nt, dsi, NT35510_P1_SETAVDD,
                                NT35510_P1_AVDD_LEN,
                                nt->conf->avdd);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_BT1CTR,
                                NT35510_P1_BT1CTR_LEN,
                                nt->conf->bt1ctr);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SETAVEE,
                                NT35510_P1_AVEE_LEN,
                                nt->conf->avee);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_BT2CTR,
                                NT35510_P1_BT2CTR_LEN,
                                nt->conf->bt2ctr);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SETVGH,
                                NT35510_P1_VGH_LEN,
                                nt->conf->vgh);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_BT4CTR,
                                NT35510_P1_BT4CTR_LEN,
                                nt->conf->bt4ctr);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_VGHCTR,
                                ARRAY_SIZE(nt35510_vgh_on),
                                nt35510_vgh_on);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SETVGL,
                                NT35510_P1_VGL_LEN,
                                nt->conf->vgl);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_BT5CTR,
                                NT35510_P1_BT5CTR_LEN,
                                nt->conf->bt5ctr);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SETVGP,
                                NT35510_P1_VGP_LEN,
                                nt->conf->vgp);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SETVGN,
                                NT35510_P1_VGN_LEN,
                                nt->conf->vgn);
        if (ret)
                return ret;

        /* Typically 10 ms */
        usleep_range(10000, 20000);

        return 0;
}

/**
 * nt35510_setup_display() - set up display config in page 0
 * @nt: the display instance to set up
 */
static int nt35510_setup_display(struct nt35510 *nt)
{
        struct mipi_dsi_device *dsi = to_mipi_dsi_device(nt->dev);
        const struct nt35510_config *conf = nt->conf;
        u8 dopctr[NT35510_P0_DOPCTR_LEN];
        u8 gseqctr[NT35510_P0_GSEQCTR_LEN];
        u8 dpfrctr[NT35510_P0_DPFRCTR1_LEN];
        /* FIXME: set up any rotation (assume none for now) */
        u8 addr_mode = NT35510_ROTATE_0_SETTING;
        u8 val;
        int ret;

        /* Enable TE, EoTP and RGB pixel format */
        dopctr[0] = NT35510_DOPCTR_0_DSITE | NT35510_DOPCTR_0_EOTP |
                NT35510_DOPCTR_0_N565;
        dopctr[1] = NT35510_DOPCTR_1_CTB;
        ret = nt35510_send_long(nt, dsi, NT35510_P0_DOPCTR,
                                NT35510_P0_DOPCTR_LEN,
                                dopctr);
        if (ret)
                return ret;

        ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_ADDRESS_MODE, &addr_mode,
                                 sizeof(addr_mode));
        if (ret < 0)
                return ret;

        /*
         * Source data hold time, default 0x05 = 2.5us
         * 0x00..0x3F = 0 .. 31.5us in steps of 0.5us
         * 0x0A = 5us
         */
        val = 0x0A;
        ret = mipi_dsi_dcs_write(dsi, NT35510_P0_SDHDTCTR, &val,
                                 sizeof(val));
        if (ret < 0)
                return ret;

        /* EQ control for gate signals, 0x00 = 0 us */
        gseqctr[0] = 0x00;
        gseqctr[1] = 0x00;
        ret = nt35510_send_long(nt, dsi, NT35510_P0_GSEQCTR,
                                NT35510_P0_GSEQCTR_LEN,
                                gseqctr);
        if (ret)
                return ret;

        ret = nt35510_send_long(nt, dsi, NT35510_P0_SDEQCTR,
                                NT35510_P0_SDEQCTR_LEN,
                                conf->sdeqctr);
        if (ret)
                return ret;

        ret = mipi_dsi_dcs_write(dsi, NT35510_P0_SDVPCTR,
                                 &conf->sdvpctr, 1);
        if (ret < 0)
                return ret;

        /*
         * Display timing control for active and idle off mode:
         * the first byte contains
         * the two high bits of T1A and second byte the low 8 bits, and
         * the valid range is 0x100 (257) to 0x3ff (1023) representing
         * 258..1024 (+1) pixel clock ticks for one scanline. At 20MHz pixel
         * clock this covers the range of 12.90us .. 51.20us in steps of
         * 0.05us, the default is 0x184 (388) representing 389 ticks.
         * The third byte is VBPDA, vertical back porch display active
         * and the fourth VFPDA, vertical front porch display active,
         * both given in number of scanlines in the range 0x02..0xff
         * for 2..255 scanlines. The fifth byte is 2 bits selecting
         * PSEL for active and idle off mode, how much the 20MHz clock
         * is divided by 0..3.  This needs to be adjusted to get the right
         * frame rate.
         */
        dpfrctr[0] = (conf->t1 >> 8) & 0xFF;
        dpfrctr[1] = conf->t1 & 0xFF;
        /* Vertical back porch */
        dpfrctr[2] = conf->vbp;
        /* Vertical front porch */
        dpfrctr[3] = conf->vfp;
        dpfrctr[4] = conf->psel;
        ret = nt35510_send_long(nt, dsi, NT35510_P0_DPFRCTR1,
                                NT35510_P0_DPFRCTR1_LEN,
                                dpfrctr);
        if (ret)
                return ret;
        /* For idle and partial idle off mode we decrease front porch by one */
        dpfrctr[3]--;
        ret = nt35510_send_long(nt, dsi, NT35510_P0_DPFRCTR2,
                                NT35510_P0_DPFRCTR2_LEN,
                                dpfrctr);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P0_DPFRCTR3,
                                NT35510_P0_DPFRCTR3_LEN,
                                dpfrctr);
        if (ret)
                return ret;

        /* Enable TE on vblank */
        ret = mipi_dsi_dcs_set_tear_on(dsi, MIPI_DSI_DCS_TEAR_MODE_VBLANK);
        if (ret)
                return ret;

        /* Turn on the pads? */
        ret = nt35510_send_long(nt, dsi, NT35510_P0_DPMCTR12,
                                NT35510_P0_DPMCTR12_LEN,
                                conf->dpmctr12);
        if (ret)
                return ret;

        return 0;
}

static int nt35510_set_brightness(struct backlight_device *bl)
{
        struct nt35510 *nt = bl_get_data(bl);
        struct mipi_dsi_device *dsi = to_mipi_dsi_device(nt->dev);
        u8 brightness = bl->props.brightness;
        int ret;

        dev_dbg(nt->dev, "set brightness %d\n", brightness);
        ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
                                 &brightness,
                                 sizeof(brightness));
        if (ret < 0)
                return ret;

        return 0;
}

static const struct backlight_ops nt35510_bl_ops = {
        .update_status = nt35510_set_brightness,
};

/*
 * This power-on sequence
 */
static int nt35510_power_on(struct nt35510 *nt)
{
        struct mipi_dsi_device *dsi = to_mipi_dsi_device(nt->dev);
        int ret;

        ret = regulator_bulk_enable(ARRAY_SIZE(nt->supplies), nt->supplies);
        if (ret < 0) {
                dev_err(nt->dev, "unable to enable regulators\n");
                return ret;
        }

        /* Toggle RESET in accordance with datasheet page 370 */
        if (nt->reset_gpio) {
                gpiod_set_value(nt->reset_gpio, 1);
                /* Active min 10 us according to datasheet, let's say 20 */
                usleep_range(20, 1000);
                gpiod_set_value(nt->reset_gpio, 0);
                /*
                 * 5 ms during sleep mode, 120 ms during sleep out mode
                 * according to datasheet, let's use 120-140 ms.
                 */
                usleep_range(120000, 140000);
        }

        ret = nt35510_send_long(nt, dsi, MCS_CMD_MTP_READ_PARAM,
                                ARRAY_SIZE(nt35510_mauc_mtp_read_param),
                                nt35510_mauc_mtp_read_param);
        if (ret)
                return ret;

        ret = nt35510_send_long(nt, dsi, MCS_CMD_MTP_READ_SETTING,
                                ARRAY_SIZE(nt35510_mauc_mtp_read_setting),
                                nt35510_mauc_mtp_read_setting);
        if (ret)
                return ret;

        nt35510_read_id(nt);

        /* Set up stuff in  manufacturer control, page 1 */
        ret = nt35510_send_long(nt, dsi, MCS_CMD_MAUCCTR,
                                ARRAY_SIZE(nt35510_mauc_select_page_1),
                                nt35510_mauc_select_page_1);
        if (ret)
                return ret;

        ret = nt35510_setup_power(nt);
        if (ret)
                return ret;

        ret = nt35510_send_long(nt, dsi, NT35510_P1_SET_GAMMA_RED_POS,
                                NT35510_P1_GAMMA_LEN,
                                nt->conf->gamma_corr_pos_r);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SET_GAMMA_GREEN_POS,
                                NT35510_P1_GAMMA_LEN,
                                nt->conf->gamma_corr_pos_g);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SET_GAMMA_BLUE_POS,
                                NT35510_P1_GAMMA_LEN,
                                nt->conf->gamma_corr_pos_b);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SET_GAMMA_RED_NEG,
                                NT35510_P1_GAMMA_LEN,
                                nt->conf->gamma_corr_neg_r);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SET_GAMMA_GREEN_NEG,
                                NT35510_P1_GAMMA_LEN,
                                nt->conf->gamma_corr_neg_g);
        if (ret)
                return ret;
        ret = nt35510_send_long(nt, dsi, NT35510_P1_SET_GAMMA_BLUE_NEG,
                                NT35510_P1_GAMMA_LEN,
                                nt->conf->gamma_corr_neg_b);
        if (ret)
                return ret;

        /* Set up stuff in  manufacturer control, page 0 */
        ret = nt35510_send_long(nt, dsi, MCS_CMD_MAUCCTR,
                                ARRAY_SIZE(nt35510_mauc_select_page_0),
                                nt35510_mauc_select_page_0);
        if (ret)
                return ret;

        ret = nt35510_setup_display(nt);
        if (ret)
                return ret;

        return 0;
}

static int nt35510_power_off(struct nt35510 *nt)
{
        int ret;

        ret = regulator_bulk_disable(ARRAY_SIZE(nt->supplies), nt->supplies);
        if (ret)
                return ret;

        if (nt->reset_gpio)
                gpiod_set_value(nt->reset_gpio, 1);

        return 0;
}

static int nt35510_unprepare(struct drm_panel *panel)
{
        struct nt35510 *nt = panel_to_nt35510(panel);
        struct mipi_dsi_device *dsi = to_mipi_dsi_device(nt->dev);
        int ret;

        ret = mipi_dsi_dcs_set_display_off(dsi);
        if (ret) {
                dev_err(nt->dev, "failed to turn display off (%d)\n", ret);
                return ret;
        }
        usleep_range(10000, 20000);

        /* Enter sleep mode */
        ret = mipi_dsi_dcs_enter_sleep_mode(dsi);
        if (ret) {
                dev_err(nt->dev, "failed to enter sleep mode (%d)\n", ret);
                return ret;
        }

        /* Wait 4 frames, how much is that 5ms in the vendor driver */
        usleep_range(5000, 10000);

        ret = nt35510_power_off(nt);
        if (ret)
                return ret;

        return 0;
}

static int nt35510_prepare(struct drm_panel *panel)
{
        struct nt35510 *nt = panel_to_nt35510(panel);
        struct mipi_dsi_device *dsi = to_mipi_dsi_device(nt->dev);
        int ret;

        ret = nt35510_power_on(nt);
        if (ret)
                return ret;

        /* Exit sleep mode */
        ret = mipi_dsi_dcs_exit_sleep_mode(dsi);
        if (ret) {
                dev_err(nt->dev, "failed to exit sleep mode (%d)\n", ret);
                return ret;
        }
        /* Up to 120 ms */
        usleep_range(120000, 150000);

        ret = mipi_dsi_dcs_set_display_on(dsi);
        if (ret) {
                dev_err(nt->dev, "failed to turn display on (%d)\n", ret);
                return ret;
        }
        /* Some 10 ms */
        usleep_range(10000, 20000);

        return 0;
}

static int nt35510_get_modes(struct drm_panel *panel,
                             struct drm_connector *connector)
{
        struct nt35510 *nt = panel_to_nt35510(panel);
        struct drm_display_mode *mode;
        struct drm_display_info *info;

        info = &connector->display_info;
        info->width_mm = nt->conf->width_mm;
        info->height_mm = nt->conf->height_mm;
        mode = drm_mode_duplicate(connector->dev, &nt->conf->mode);
        if (!mode) {
                dev_err(panel->dev, "bad mode or failed to add mode\n");
                return -EINVAL;
        }
        drm_mode_set_name(mode);
        mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;

        mode->width_mm = nt->conf->width_mm;
        mode->height_mm = nt->conf->height_mm;
        drm_mode_probed_add(connector, mode);

        return 1; /* Number of modes */
}

static const struct drm_panel_funcs nt35510_drm_funcs = {
        .unprepare = nt35510_unprepare,
        .prepare = nt35510_prepare,
        .get_modes = nt35510_get_modes,
};

static int nt35510_probe(struct mipi_dsi_device *dsi)
{
        struct device *dev = &dsi->dev;
        struct nt35510 *nt;
        int ret;

        nt = devm_kzalloc(dev, sizeof(struct nt35510), GFP_KERNEL);
        if (!nt)
                return -ENOMEM;
        mipi_dsi_set_drvdata(dsi, nt);
        nt->dev = dev;

        dsi->lanes = 2;
        dsi->format = MIPI_DSI_FMT_RGB888;
        /*
         * Datasheet suggests max HS rate for NT35510 is 250 MHz
         * (period time 4ns, see figure 7.6.4 page 365) and max LP rate is
         * 20 MHz (period time 50ns, see figure 7.6.6. page 366).
         * However these frequencies appear in source code for the Hydis
         * HVA40WV1 panel and setting up the LP frequency makes the panel
         * not work.
         *
         * TODO: if other panels prove to be closer to the datasheet,
         * maybe make this a per-panel config in struct nt35510_config?
         */
        dsi->hs_rate = 349440000;
        dsi->lp_rate = 9600000;
        dsi->mode_flags = MIPI_DSI_CLOCK_NON_CONTINUOUS;

        /*
         * Every new incarnation of this display must have a unique
         * data entry for the system in this driver.
         */
        nt->conf = of_device_get_match_data(dev);
        if (!nt->conf) {
                dev_err(dev, "missing device configuration\n");
                return -ENODEV;
        }

        nt->supplies[0].supply = "vdd"; /* 2.3-4.8 V */
        nt->supplies[1].supply = "vddi"; /* 1.65-3.3V */
        ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(nt->supplies),
                                      nt->supplies);
        if (ret < 0)
                return ret;
        ret = regulator_set_voltage(nt->supplies[0].consumer,
                                    2300000, 4800000);
        if (ret)
                return ret;
        ret = regulator_set_voltage(nt->supplies[1].consumer,
                                    1650000, 3300000);
        if (ret)
                return ret;

        nt->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_ASIS);
        if (IS_ERR(nt->reset_gpio)) {
                dev_err(dev, "error getting RESET GPIO\n");
                return PTR_ERR(nt->reset_gpio);
        }

        drm_panel_init(&nt->panel, dev, &nt35510_drm_funcs,
                       DRM_MODE_CONNECTOR_DSI);

        /*
         * First, try to locate an external backlight (such as on GPIO)
         * if this fails, assume we will want to use the internal backlight
         * control.
         */
        ret = drm_panel_of_backlight(&nt->panel);
        if (ret) {
                dev_err(dev, "error getting external backlight %d\n", ret);
                return ret;
        }
        if (!nt->panel.backlight) {
                struct backlight_device *bl;

                bl = devm_backlight_device_register(dev, "nt35510", dev, nt,
                                                    &nt35510_bl_ops, NULL);
                if (IS_ERR(bl)) {
                        dev_err(dev, "failed to register backlight device\n");
                        return PTR_ERR(bl);
                }
                bl->props.max_brightness = 255;
                bl->props.brightness = 255;
                bl->props.power = FB_BLANK_POWERDOWN;
                nt->panel.backlight = bl;
        }

        drm_panel_add(&nt->panel);

        ret = mipi_dsi_attach(dsi);
        if (ret < 0)
                drm_panel_remove(&nt->panel);

        return 0;
}

static int nt35510_remove(struct mipi_dsi_device *dsi)
{
        struct nt35510 *nt = mipi_dsi_get_drvdata(dsi);
        int ret;

        mipi_dsi_detach(dsi);
        /* Power off */
        ret = nt35510_power_off(nt);
        drm_panel_remove(&nt->panel);

        return ret;
}

/*
 * These gamma correction values are 10bit tuples, so only bits 0 and 1 is
 * ever used in the first byte. They form a positive and negative gamma
 * correction curve for each color, values must be strictly higher for each
 * step on the curve. As can be seen these default curves goes from 0x0001
 * to 0x03FE.
 */
#define NT35510_GAMMA_POS_DEFAULT 0x00, 0x01, 0x00, 0x43, 0x00, \
                0x6B, 0x00, 0x87, 0x00, 0xA3, 0x00, 0xCE, 0x00, 0xF1, 0x01, \
                0x27, 0x01, 0x53, 0x01, 0x98, 0x01, 0xCE, 0x02, 0x22, 0x02, \
                0x83, 0x02, 0x78, 0x02, 0x9E, 0x02, 0xDD, 0x03, 0x00, 0x03, \
                0x2E, 0x03, 0x54, 0x03, 0x7F, 0x03, 0x95, 0x03, 0xB3, 0x03, \
                0xC2, 0x03, 0xE1, 0x03, 0xF1, 0x03, 0xFE

#define NT35510_GAMMA_NEG_DEFAULT 0x00, 0x01, 0x00, 0x43, 0x00, \
                0x6B, 0x00, 0x87, 0x00, 0xA3, 0x00, 0xCE, 0x00, 0xF1, 0x01, \
                0x27, 0x01, 0x53, 0x01, 0x98, 0x01, 0xCE, 0x02, 0x22, 0x02, \
                0x43, 0x02, 0x50, 0x02, 0x9E, 0x02, 0xDD, 0x03, 0x00, 0x03, \
                0x2E, 0x03, 0x54, 0x03, 0x7F, 0x03, 0x95, 0x03, 0xB3, 0x03, \

                0xC2, 0x03, 0xE1, 0x03, 0xF1, 0x03, 0xFE

/*
 * The Hydis HVA40WV1 panel
 */
static const struct nt35510_config nt35510_hydis_hva40wv1 = {
        .width_mm = 52,
        .height_mm = 86,
        /**
         * As the Hydis panel is used in command mode, the porches etc
         * are settings programmed internally into the NT35510 controller
         * and generated toward the physical display. As the panel is not
         * used in video mode, these are not really exposed to the DSI
         * host.
         *
         * Display frame rate control:
         * Frame rate = (20 MHz / 1) / (389 * (7 + 50 + 800)) ~= 60 Hz
         */
        .mode = {
                /* The internal pixel clock of the NT35510 is 20 MHz */
                .clock = 20000,
                .hdisplay = 480,
                .hsync_start = 480 + 2, /* HFP = 2 */
                .hsync_end = 480 + 2 + 0, /* HSync = 0 */
                .htotal = 480 + 2 + 0 + 5, /* HFP = 5 */
                .vdisplay = 800,
                .vsync_start = 800 + 2, /* VFP = 2 */
                .vsync_end = 800 + 2 + 0, /* VSync = 0 */
                .vtotal = 800 + 2 + 0 + 5, /* VBP = 5 */
                .flags = 0,
        },
        /* 0x09: AVDD = 5.6V */
        .avdd = { 0x09, 0x09, 0x09 },
        /* 0x34: PCK = Hsync/2, BTP = 2 x VDDB */
        .bt1ctr = { 0x34, 0x34, 0x34 },
        /* 0x09: AVEE = -5.6V */
        .avee = { 0x09, 0x09, 0x09 },
        /* 0x24: NCK = Hsync/2, BTN =  -2 x VDDB */
        .bt2ctr = { 0x24, 0x24, 0x24 },
        /* 0x05 = 12V */
        .vgh = { 0x05, 0x05, 0x05 },
        /* 0x24: NCKA = Hsync/2, VGH = 2 x AVDD - AVEE */
        .bt4ctr = { 0x24, 0x24, 0x24 },
        /* 0x0B = -13V */
        .vgl = { 0x0B, 0x0B, 0x0B },
        /* 0x24: LCKA = Hsync, VGL = AVDD + VCL - AVDD */
        .bt5ctr = { 0x24, 0x24, 0x24 },
        /* VGMP: 0x0A3 = 5.0375V, VGSP = 0V */
        .vgp = { 0x00, 0xA3, 0x00 },
        /* VGMP: 0x0A3 = 5.0375V, VGSP = 0V */
        .vgn = { 0x00, 0xA3, 0x00 },
        /* SDEQCTR: source driver EQ mode 2, 2.5 us rise time on each step */
        .sdeqctr = { 0x01, 0x05, 0x05, 0x05 },
        /* SDVPCTR: Normal operation off color during v porch */
        .sdvpctr = 0x01,
        /* T1: number of pixel clocks on one scanline: 0x184 = 389 clocks */
        .t1 = 0x0184,
        /* VBP: vertical back porch toward the panel */
        .vbp = 7,
        /* VFP: vertical front porch toward the panel */
        .vfp = 50,
        /* PSEL: divide pixel clock 20MHz with 1 (no clock downscaling) */
        .psel = 0,
        /* DPTMCTR12: 0x03: LVGL = VGLX, overlap mode, swap R->L O->E */
        .dpmctr12 = { 0x03, 0x00, 0x00, },
        /* Default gamma correction values */
        .gamma_corr_pos_r = { NT35510_GAMMA_POS_DEFAULT },
        .gamma_corr_pos_g = { NT35510_GAMMA_POS_DEFAULT },
        .gamma_corr_pos_b = { NT35510_GAMMA_POS_DEFAULT },
        .gamma_corr_neg_r = { NT35510_GAMMA_NEG_DEFAULT },
        .gamma_corr_neg_g = { NT35510_GAMMA_NEG_DEFAULT },
        .gamma_corr_neg_b = { NT35510_GAMMA_NEG_DEFAULT },
};

static const struct of_device_id nt35510_of_match[] = {
        {
                .compatible = "hydis,hva40wv1",
                .data = &nt35510_hydis_hva40wv1,
        },
        { }
};
MODULE_DEVICE_TABLE(of, nt35510_of_match);

static struct mipi_dsi_driver nt35510_driver = {
        .probe = nt35510_probe,
        .remove = nt35510_remove,
        .driver = {
                .name = "panel-novatek-nt35510",
                .of_match_table = nt35510_of_match,
        },
};
module_mipi_dsi_driver(nt35510_driver);

MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
MODULE_DESCRIPTION("NT35510-based panel driver");
MODULE_LICENSE("GPL v2");