/*
 * MIPI Display Bus Interface (DBI) LCD controller support
 *
 * Copyright 2016 Noralf Trønnes
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/tinydrm/mipi-dbi.h>
#include <drm/tinydrm/tinydrm-helpers.h>
#include <linux/debugfs.h>
#include <linux/dma-buf.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/regulator/consumer.h>
#include <linux/spi/spi.h>
#include <video/mipi_display.h>

#define MIPI_DBI_MAX_SPI_READ_SPEED 2000000 /* 2MHz */

#define DCS_POWER_MODE_DISPLAY                  BIT(2)
#define DCS_POWER_MODE_DISPLAY_NORMAL_MODE      BIT(3)
#define DCS_POWER_MODE_SLEEP_MODE               BIT(4)
#define DCS_POWER_MODE_PARTIAL_MODE             BIT(5)
#define DCS_POWER_MODE_IDLE_MODE                BIT(6)
#define DCS_POWER_MODE_RESERVED_MASK            (BIT(0) | BIT(1) | BIT(7))

/**
 * DOC: overview
 *
 * This library provides helpers for MIPI Display Bus Interface (DBI)
 * compatible display controllers.
 *
 * Many controllers for tiny lcd displays are MIPI compliant and can use this
 * library. If a controller uses registers 0x2A and 0x2B to set the area to
 * update and uses register 0x2C to write to frame memory, it is most likely
 * MIPI compliant.
 *
 * Only MIPI Type 1 displays are supported since a full frame memory is needed.
 *
 * There are 3 MIPI DBI implementation types:
 *
 * A. Motorola 6800 type parallel bus
 *
 * B. Intel 8080 type parallel bus
 *
 * C. SPI type with 3 options:
 *
 *    1. 9-bit with the Data/Command signal as the ninth bit
 *    2. Same as above except it's sent as 16 bits
 *    3. 8-bit with the Data/Command signal as a separate D/CX pin
 *
 * Currently mipi_dbi only supports Type C options 1 and 3 with
 * mipi_dbi_spi_init().
 */

#define MIPI_DBI_DEBUG_COMMAND(cmd, data, len) \
({ \
        if (!len) \
                DRM_DEBUG_DRIVER("cmd=%02x\n", cmd); \
        else if (len <= 32) \
                DRM_DEBUG_DRIVER("cmd=%02x, par=%*ph\n", cmd, (int)len, data);\
        else \
                DRM_DEBUG_DRIVER("cmd=%02x, len=%zu\n", cmd, len); \
})

static const u8 mipi_dbi_dcs_read_commands[] = {
        MIPI_DCS_GET_DISPLAY_ID,
        MIPI_DCS_GET_RED_CHANNEL,
        MIPI_DCS_GET_GREEN_CHANNEL,
        MIPI_DCS_GET_BLUE_CHANNEL,
        MIPI_DCS_GET_DISPLAY_STATUS,
        MIPI_DCS_GET_POWER_MODE,
        MIPI_DCS_GET_ADDRESS_MODE,
        MIPI_DCS_GET_PIXEL_FORMAT,
        MIPI_DCS_GET_DISPLAY_MODE,
        MIPI_DCS_GET_SIGNAL_MODE,
        MIPI_DCS_GET_DIAGNOSTIC_RESULT,
        MIPI_DCS_READ_MEMORY_START,
        MIPI_DCS_READ_MEMORY_CONTINUE,
        MIPI_DCS_GET_SCANLINE,
        MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
        MIPI_DCS_GET_CONTROL_DISPLAY,
        MIPI_DCS_GET_POWER_SAVE,
        MIPI_DCS_GET_CABC_MIN_BRIGHTNESS,
        MIPI_DCS_READ_DDB_START,
        MIPI_DCS_READ_DDB_CONTINUE,
        0, /* sentinel */
};

static bool mipi_dbi_command_is_read(struct mipi_dbi *mipi, u8 cmd)
{
        unsigned int i;

        if (!mipi->read_commands)
                return false;

        for (i = 0; i < 0xff; i++) {
                if (!mipi->read_commands[i])
                        return false;
                if (cmd == mipi->read_commands[i])
                        return true;
        }

        return false;
}

/**
 * mipi_dbi_command_read - MIPI DCS read command
 * @mipi: MIPI structure
 * @cmd: Command
 * @val: Value read
 *
 * Send MIPI DCS read command to the controller.
 *
 * Returns:
 * Zero on success, negative error code on failure.
 */
int mipi_dbi_command_read(struct mipi_dbi *mipi, u8 cmd, u8 *val)
{
        if (!mipi->read_commands)
                return -EACCES;

        if (!mipi_dbi_command_is_read(mipi, cmd))
                return -EINVAL;

        return mipi_dbi_command_buf(mipi, cmd, val, 1);
}
EXPORT_SYMBOL(mipi_dbi_command_read);

/**
 * mipi_dbi_command_buf - MIPI DCS command with parameter(s) in an array
 * @mipi: MIPI structure
 * @cmd: Command
 * @data: Parameter buffer
 * @len: Buffer length
 *
 * Returns:
 * Zero on success, negative error code on failure.
 */
int mipi_dbi_command_buf(struct mipi_dbi *mipi, u8 cmd, u8 *data, size_t len)
{
        int ret;

        mutex_lock(&mipi->cmdlock);
        ret = mipi->command(mipi, cmd, data, len);
        mutex_unlock(&mipi->cmdlock);

        return ret;
}
EXPORT_SYMBOL(mipi_dbi_command_buf);

static int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb,
                                struct drm_clip_rect *clip, bool swap)
{
        struct drm_gem_cma_object *cma_obj = drm_fb_cma_get_gem_obj(fb, 0);
        struct dma_buf_attachment *import_attach = cma_obj->base.import_attach;
        struct drm_format_name_buf format_name;
        void *src = cma_obj->vaddr;
        int ret = 0;

        if (import_attach) {
                ret = dma_buf_begin_cpu_access(import_attach->dmabuf,
                                               DMA_FROM_DEVICE);
                if (ret)
                        return ret;
        }

        switch (fb->format->format) {
        case DRM_FORMAT_RGB565:
                if (swap)
                        tinydrm_swab16(dst, src, fb, clip);
                else
                        tinydrm_memcpy(dst, src, fb, clip);
                break;
        case DRM_FORMAT_XRGB8888:
                tinydrm_xrgb8888_to_rgb565(dst, src, fb, clip, swap);
                break;
        default:
                dev_err_once(fb->dev->dev, "Format is not supported: %s\n",
                             drm_get_format_name(fb->format->format,
                                                 &format_name));
                return -EINVAL;
        }

        if (import_attach)
                ret = dma_buf_end_cpu_access(import_attach->dmabuf,
                                             DMA_FROM_DEVICE);
        return ret;
}

static int mipi_dbi_fb_dirty(struct drm_framebuffer *fb,
                             struct drm_file *file_priv,
                             unsigned int flags, unsigned int color,
                             struct drm_clip_rect *clips,
                             unsigned int num_clips)
{
        struct drm_gem_cma_object *cma_obj = drm_fb_cma_get_gem_obj(fb, 0);
        struct tinydrm_device *tdev = fb->dev->dev_private;
        struct mipi_dbi *mipi = mipi_dbi_from_tinydrm(tdev);
        bool swap = mipi->swap_bytes;
        struct drm_clip_rect clip;
        int ret = 0;
        bool full;
        void *tr;

        mutex_lock(&tdev->dirty_lock);

        if (!mipi->enabled)
                goto out_unlock;

        /* fbdev can flush even when we're not interested */
        if (tdev->pipe.plane.fb != fb)
                goto out_unlock;

        full = tinydrm_merge_clips(&clip, clips, num_clips, flags,
                                   fb->width, fb->height);

        DRM_DEBUG("Flushing [FB:%d] x1=%u, x2=%u, y1=%u, y2=%u\n", fb->base.id,
                  clip.x1, clip.x2, clip.y1, clip.y2);

        if (!mipi->dc || !full || swap ||
            fb->format->format == DRM_FORMAT_XRGB8888) {
                tr = mipi->tx_buf;
                ret = mipi_dbi_buf_copy(mipi->tx_buf, fb, &clip, swap);
                if (ret)
                        goto out_unlock;
        } else {
                tr = cma_obj->vaddr;
        }

        mipi_dbi_command(mipi, MIPI_DCS_SET_COLUMN_ADDRESS,
                         (clip.x1 >> 8) & 0xFF, clip.x1 & 0xFF,
                         (clip.x2 >> 8) & 0xFF, (clip.x2 - 1) & 0xFF);
        mipi_dbi_command(mipi, MIPI_DCS_SET_PAGE_ADDRESS,
                         (clip.y1 >> 8) & 0xFF, clip.y1 & 0xFF,
                         (clip.y2 >> 8) & 0xFF, (clip.y2 - 1) & 0xFF);

        ret = mipi_dbi_command_buf(mipi, MIPI_DCS_WRITE_MEMORY_START, tr,
                                (clip.x2 - clip.x1) * (clip.y2 - clip.y1) * 2);

out_unlock:
        mutex_unlock(&tdev->dirty_lock);

        if (ret)
                dev_err_once(fb->dev->dev, "Failed to update display %d\n",
                             ret);

        return ret;
}

static const struct drm_framebuffer_funcs mipi_dbi_fb_funcs = {
        .destroy        = drm_gem_fb_destroy,
        .create_handle  = drm_gem_fb_create_handle,
        .dirty          = mipi_dbi_fb_dirty,
};

/**
 * mipi_dbi_pipe_enable - MIPI DBI pipe enable helper
 * @pipe: Display pipe
 * @crtc_state: CRTC state
 *
 * This function enables backlight. Drivers can use this as their
 * &drm_simple_display_pipe_funcs->enable callback.
 */
void mipi_dbi_pipe_enable(struct drm_simple_display_pipe *pipe,
                          struct drm_crtc_state *crtc_state)
{
        struct tinydrm_device *tdev = pipe_to_tinydrm(pipe);
        struct mipi_dbi *mipi = mipi_dbi_from_tinydrm(tdev);
        struct drm_framebuffer *fb = pipe->plane.fb;

        DRM_DEBUG_KMS("\n");

        mipi->enabled = true;
        if (fb)
                fb->funcs->dirty(fb, NULL, 0, 0, NULL, 0);

        tinydrm_enable_backlight(mipi->backlight);
}
EXPORT_SYMBOL(mipi_dbi_pipe_enable);

static void mipi_dbi_blank(struct mipi_dbi *mipi)
{
        struct drm_device *drm = mipi->tinydrm.drm;
        u16 height = drm->mode_config.min_height;
        u16 width = drm->mode_config.min_width;
        size_t len = width * height * 2;

        memset(mipi->tx_buf, 0, len);

        mipi_dbi_command(mipi, MIPI_DCS_SET_COLUMN_ADDRESS, 0, 0,
                         (width >> 8) & 0xFF, (width - 1) & 0xFF);
        mipi_dbi_command(mipi, MIPI_DCS_SET_PAGE_ADDRESS, 0, 0,
                         (height >> 8) & 0xFF, (height - 1) & 0xFF);
        mipi_dbi_command_buf(mipi, MIPI_DCS_WRITE_MEMORY_START,
                             (u8 *)mipi->tx_buf, len);
}

/**
 * mipi_dbi_pipe_disable - MIPI DBI pipe disable helper
 * @pipe: Display pipe
 *
 * This function disables backlight if present or if not the
 * display memory is blanked. Drivers can use this as their
 * &drm_simple_display_pipe_funcs->disable callback.
 */
void mipi_dbi_pipe_disable(struct drm_simple_display_pipe *pipe)
{
        struct tinydrm_device *tdev = pipe_to_tinydrm(pipe);
        struct mipi_dbi *mipi = mipi_dbi_from_tinydrm(tdev);

        DRM_DEBUG_KMS("\n");

        mipi->enabled = false;

        if (mipi->backlight)
                tinydrm_disable_backlight(mipi->backlight);
        else
                mipi_dbi_blank(mipi);
}
EXPORT_SYMBOL(mipi_dbi_pipe_disable);

static const uint32_t mipi_dbi_formats[] = {
        DRM_FORMAT_RGB565,
        DRM_FORMAT_XRGB8888,
};

/**
 * mipi_dbi_init - MIPI DBI initialization
 * @dev: Parent device
 * @mipi: &mipi_dbi structure to initialize
 * @pipe_funcs: Display pipe functions
 * @driver: DRM driver
 * @mode: Display mode
 * @rotation: Initial rotation in degrees Counter Clock Wise
 *
 * This function initializes a &mipi_dbi structure and it's underlying
 * @tinydrm_device. It also sets up the display pipeline.
 *
 * Supported formats: Native RGB565 and emulated XRGB8888.
 *
 * Objects created by this function will be automatically freed on driver
 * detach (devres).
 *
 * Returns:
 * Zero on success, negative error code on failure.
 */
int mipi_dbi_init(struct device *dev, struct mipi_dbi *mipi,
                  const struct drm_simple_display_pipe_funcs *pipe_funcs,
                  struct drm_driver *driver,
                  const struct drm_display_mode *mode, unsigned int rotation)
{
        size_t bufsize = mode->vdisplay * mode->hdisplay * sizeof(u16);
        struct tinydrm_device *tdev = &mipi->tinydrm;
        int ret;

        if (!mipi->command)
                return -EINVAL;

        mutex_init(&mipi->cmdlock);

        mipi->tx_buf = devm_kmalloc(dev, bufsize, GFP_KERNEL);
        if (!mipi->tx_buf)
                return -ENOMEM;

        ret = devm_tinydrm_init(dev, tdev, &mipi_dbi_fb_funcs, driver);
        if (ret)
                return ret;

        /* TODO: Maybe add DRM_MODE_CONNECTOR_SPI */
        ret = tinydrm_display_pipe_init(tdev, pipe_funcs,
                                        DRM_MODE_CONNECTOR_VIRTUAL,
                                        mipi_dbi_formats,
                                        ARRAY_SIZE(mipi_dbi_formats), mode,
                                        rotation);
        if (ret)
                return ret;

        tdev->drm->mode_config.preferred_depth = 16;
        mipi->rotation = rotation;

        drm_mode_config_reset(tdev->drm);

        DRM_DEBUG_KMS("preferred_depth=%u, rotation = %u\n",
                      tdev->drm->mode_config.preferred_depth, rotation);

        return 0;
}
EXPORT_SYMBOL(mipi_dbi_init);

/**
 * mipi_dbi_hw_reset - Hardware reset of controller
 * @mipi: MIPI DBI structure
 *
 * Reset controller if the &mipi_dbi->reset gpio is set.
 */
void mipi_dbi_hw_reset(struct mipi_dbi *mipi)
{
        if (!mipi->reset)
                return;

        gpiod_set_value_cansleep(mipi->reset, 0);
        msleep(20);
        gpiod_set_value_cansleep(mipi->reset, 1);
        msleep(120);
}
EXPORT_SYMBOL(mipi_dbi_hw_reset);

/**
 * mipi_dbi_display_is_on - Check if display is on
 * @mipi: MIPI DBI structure
 *
 * This function checks the Power Mode register (if readable) to see if
 * display output is turned on. This can be used to see if the bootloader
 * has already turned on the display avoiding flicker when the pipeline is
 * enabled.
 *
 * Returns:
 * true if the display can be verified to be on, false otherwise.
 */
bool mipi_dbi_display_is_on(struct mipi_dbi *mipi)
{
        u8 val;

        if (mipi_dbi_command_read(mipi, MIPI_DCS_GET_POWER_MODE, &val))
                return false;

        val &= ~DCS_POWER_MODE_RESERVED_MASK;

        if (val != (DCS_POWER_MODE_DISPLAY |
            DCS_POWER_MODE_DISPLAY_NORMAL_MODE | DCS_POWER_MODE_SLEEP_MODE))
                return false;

        DRM_DEBUG_DRIVER("Display is ON\n");

        return true;
}
EXPORT_SYMBOL(mipi_dbi_display_is_on);

#if IS_ENABLED(CONFIG_SPI)

/*
 * Many controllers have a max speed of 10MHz, but can be pushed way beyond
 * that. Increase reliability by running pixel data at max speed and the rest
 * at 10MHz, preventing transfer glitches from messing up the init settings.
 */
static u32 mipi_dbi_spi_cmd_max_speed(struct spi_device *spi, size_t len)
{
        if (len > 64)
                return 0; /* use default */

        return min_t(u32, 10000000, spi->max_speed_hz);
}

/*
 * MIPI DBI Type C Option 1
 *
 * If the SPI controller doesn't have 9 bits per word support,
 * use blocks of 9 bytes to send 8x 9-bit words using a 8-bit SPI transfer.
 * Pad partial blocks with MIPI_DCS_NOP (zero).
 * This is how the D/C bit (x) is added:
 *     x7654321
 *     0x765432
 *     10x76543
 *     210x7654
 *     3210x765
 *     43210x76
 *     543210x7
 *     6543210x
 *     76543210
 */

static int mipi_dbi_spi1e_transfer(struct mipi_dbi *mipi, int dc,
                                   const void *buf, size_t len,
                                   unsigned int bpw)
{
        bool swap_bytes = (bpw == 16 && tinydrm_machine_little_endian());
        size_t chunk, max_chunk = mipi->tx_buf9_len;
        struct spi_device *spi = mipi->spi;
        struct spi_transfer tr = {
                .tx_buf = mipi->tx_buf9,
                .bits_per_word = 8,
        };
        struct spi_message m;
        const u8 *src = buf;
        int i, ret;
        u8 *dst;

        if (drm_debug & DRM_UT_DRIVER)
                pr_debug("[drm:%s] dc=%d, max_chunk=%zu, transfers:\n",
                         __func__, dc, max_chunk);

        tr.speed_hz = mipi_dbi_spi_cmd_max_speed(spi, len);
        spi_message_init_with_transfers(&m, &tr, 1);

        if (!dc) {
                if (WARN_ON_ONCE(len != 1))
                        return -EINVAL;

                /* Command: pad no-op's (zeroes) at beginning of block */
                dst = mipi->tx_buf9;
                memset(dst, 0, 9);
                dst[8] = *src;
                tr.len = 9;

                tinydrm_dbg_spi_message(spi, &m);

                return spi_sync(spi, &m);
        }

        /* max with room for adding one bit per byte */
        max_chunk = max_chunk / 9 * 8;
        /* but no bigger than len */
        max_chunk = min(max_chunk, len);
        /* 8 byte blocks */
        max_chunk = max_t(size_t, 8, max_chunk & ~0x7);

        while (len) {
                size_t added = 0;

                chunk = min(len, max_chunk);
                len -= chunk;
                dst = mipi->tx_buf9;

                if (chunk < 8) {
                        u8 val, carry = 0;

                        /* Data: pad no-op's (zeroes) at end of block */
                        memset(dst, 0, 9);

                        if (swap_bytes) {
                                for (i = 1; i < (chunk + 1); i++) {
                                        val = src[1];
                                        *dst++ = carry | BIT(8 - i) | (val >> i);
                                        carry = val << (8 - i);
                                        i++;
                                        val = src[0];
                                        *dst++ = carry | BIT(8 - i) | (val >> i);
                                        carry = val << (8 - i);
                                        src += 2;
                                }
                                *dst++ = carry;
                        } else {
                                for (i = 1; i < (chunk + 1); i++) {
                                        val = *src++;
                                        *dst++ = carry | BIT(8 - i) | (val >> i);
                                        carry = val << (8 - i);
                                }
                                *dst++ = carry;
                        }

                        chunk = 8;
                        added = 1;
                } else {
                        for (i = 0; i < chunk; i += 8) {
                                if (swap_bytes) {
                                        *dst++ =                 BIT(7) | (src[1] >> 1);
                                        *dst++ = (src[1] << 7) | BIT(6) | (src[0] >> 2);
                                        *dst++ = (src[0] << 6) | BIT(5) | (src[3] >> 3);
                                        *dst++ = (src[3] << 5) | BIT(4) | (src[2] >> 4);
                                        *dst++ = (src[2] << 4) | BIT(3) | (src[5] >> 5);
                                        *dst++ = (src[5] << 3) | BIT(2) | (src[4] >> 6);
                                        *dst++ = (src[4] << 2) | BIT(1) | (src[7] >> 7);
                                        *dst++ = (src[7] << 1) | BIT(0);
                                        *dst++ = src[6];
                                } else {
                                        *dst++ =                 BIT(7) | (src[0] >> 1);
                                        *dst++ = (src[0] << 7) | BIT(6) | (src[1] >> 2);
                                        *dst++ = (src[1] << 6) | BIT(5) | (src[2] >> 3);
                                        *dst++ = (src[2] << 5) | BIT(4) | (src[3] >> 4);
                                        *dst++ = (src[3] << 4) | BIT(3) | (src[4] >> 5);
                                        *dst++ = (src[4] << 3) | BIT(2) | (src[5] >> 6);
                                        *dst++ = (src[5] << 2) | BIT(1) | (src[6] >> 7);
                                        *dst++ = (src[6] << 1) | BIT(0);
                                        *dst++ = src[7];
                                }

                                src += 8;
                                added++;
                        }
                }

                tr.len = chunk + added;

                tinydrm_dbg_spi_message(spi, &m);
                ret = spi_sync(spi, &m);
                if (ret)
                        return ret;
        }

        return 0;
}

static int mipi_dbi_spi1_transfer(struct mipi_dbi *mipi, int dc,
                                  const void *buf, size_t len,
                                  unsigned int bpw)
{
        struct spi_device *spi = mipi->spi;
        struct spi_transfer tr = {
                .bits_per_word = 9,
        };
        const u16 *src16 = buf;
        const u8 *src8 = buf;
        struct spi_message m;
        size_t max_chunk;
        u16 *dst16;
        int ret;

        if (!tinydrm_spi_bpw_supported(spi, 9))
                return mipi_dbi_spi1e_transfer(mipi, dc, buf, len, bpw);

        tr.speed_hz = mipi_dbi_spi_cmd_max_speed(spi, len);
        max_chunk = mipi->tx_buf9_len;
        dst16 = mipi->tx_buf9;

        if (drm_debug & DRM_UT_DRIVER)
                pr_debug("[drm:%s] dc=%d, max_chunk=%zu, transfers:\n",
                         __func__, dc, max_chunk);

        max_chunk = min(max_chunk / 2, len);

        spi_message_init_with_transfers(&m, &tr, 1);
        tr.tx_buf = dst16;

        while (len) {
                size_t chunk = min(len, max_chunk);
                unsigned int i;

                if (bpw == 16 && tinydrm_machine_little_endian()) {
                        for (i = 0; i < (chunk * 2); i += 2) {
                                dst16[i]     = *src16 >> 8;
                                dst16[i + 1] = *src16++ & 0xFF;
                                if (dc) {
                                        dst16[i]     |= 0x0100;
                                        dst16[i + 1] |= 0x0100;
                                }
                        }
                } else {
                        for (i = 0; i < chunk; i++) {
                                dst16[i] = *src8++;
                                if (dc)
                                        dst16[i] |= 0x0100;
                        }
                }

                tr.len = chunk;
                len -= chunk;

                tinydrm_dbg_spi_message(spi, &m);
                ret = spi_sync(spi, &m);
                if (ret)
                        return ret;
        }

        return 0;
}

static int mipi_dbi_typec1_command(struct mipi_dbi *mipi, u8 cmd,
                                   u8 *parameters, size_t num)
{
        unsigned int bpw = (cmd == MIPI_DCS_WRITE_MEMORY_START) ? 16 : 8;
        int ret;

        if (mipi_dbi_command_is_read(mipi, cmd))
                return -ENOTSUPP;

        MIPI_DBI_DEBUG_COMMAND(cmd, parameters, num);

        ret = mipi_dbi_spi1_transfer(mipi, 0, &cmd, 1, 8);
        if (ret || !num)
                return ret;

        return mipi_dbi_spi1_transfer(mipi, 1, parameters, num, bpw);
}

/* MIPI DBI Type C Option 3 */

static int mipi_dbi_typec3_command_read(struct mipi_dbi *mipi, u8 cmd,
                                        u8 *data, size_t len)
{
        struct spi_device *spi = mipi->spi;
        u32 speed_hz = min_t(u32, MIPI_DBI_MAX_SPI_READ_SPEED,
                             spi->max_speed_hz / 2);
        struct spi_transfer tr[2] = {
                {
                        .speed_hz = speed_hz,
                        .tx_buf = &cmd,
                        .len = 1,
                }, {
                        .speed_hz = speed_hz,
                        .len = len,
                },
        };
        struct spi_message m;
        u8 *buf;
        int ret;

        if (!len)
                return -EINVAL;

        /*
         * Support non-standard 24-bit and 32-bit Nokia read commands which
         * start with a dummy clock, so we need to read an extra byte.
         */
        if (cmd == MIPI_DCS_GET_DISPLAY_ID ||
            cmd == MIPI_DCS_GET_DISPLAY_STATUS) {
                if (!(len == 3 || len == 4))
                        return -EINVAL;

                tr[1].len = len + 1;
        }

        buf = kmalloc(tr[1].len, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        tr[1].rx_buf = buf;
        gpiod_set_value_cansleep(mipi->dc, 0);

        spi_message_init_with_transfers(&m, tr, ARRAY_SIZE(tr));
        ret = spi_sync(spi, &m);
        if (ret)
                goto err_free;

        tinydrm_dbg_spi_message(spi, &m);

        if (tr[1].len == len) {
                memcpy(data, buf, len);
        } else {
                unsigned int i;

                for (i = 0; i < len; i++)
                        data[i] = (buf[i] << 1) | !!(buf[i + 1] & BIT(7));
        }

        MIPI_DBI_DEBUG_COMMAND(cmd, data, len);

err_free:
        kfree(buf);

        return ret;
}

static int mipi_dbi_typec3_command(struct mipi_dbi *mipi, u8 cmd,
                                   u8 *par, size_t num)
{
        struct spi_device *spi = mipi->spi;
        unsigned int bpw = 8;
        u32 speed_hz;
        int ret;

        if (mipi_dbi_command_is_read(mipi, cmd))
                return mipi_dbi_typec3_command_read(mipi, cmd, par, num);

        MIPI_DBI_DEBUG_COMMAND(cmd, par, num);

        gpiod_set_value_cansleep(mipi->dc, 0);
        speed_hz = mipi_dbi_spi_cmd_max_speed(spi, 1);
        ret = tinydrm_spi_transfer(spi, speed_hz, NULL, 8, &cmd, 1);
        if (ret || !num)
                return ret;

        if (cmd == MIPI_DCS_WRITE_MEMORY_START && !mipi->swap_bytes)
                bpw = 16;

        gpiod_set_value_cansleep(mipi->dc, 1);
        speed_hz = mipi_dbi_spi_cmd_max_speed(spi, num);

        return tinydrm_spi_transfer(spi, speed_hz, NULL, bpw, par, num);
}

/**
 * mipi_dbi_spi_init - Initialize MIPI DBI SPI interfaced controller
 * @spi: SPI device
 * @mipi: &mipi_dbi structure to initialize
 * @dc: D/C gpio (optional)
 *
 * This function sets &mipi_dbi->command, enables &mipi->read_commands for the
 * usual read commands. It should be followed by a call to mipi_dbi_init() or
 * a driver-specific init.
 *
 * If @dc is set, a Type C Option 3 interface is assumed, if not
 * Type C Option 1.
 *
 * If the SPI master driver doesn't support the necessary bits per word,
 * the following transformation is used:
 *
 * - 9-bit: reorder buffer as 9x 8-bit words, padded with no-op command.
 * - 16-bit: if big endian send as 8-bit, if little endian swap bytes
 *
 * Returns:
 * Zero on success, negative error code on failure.
 */
int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *mipi,
                      struct gpio_desc *dc)
{
        size_t tx_size = tinydrm_spi_max_transfer_size(spi, 0);
        struct device *dev = &spi->dev;
        int ret;

        if (tx_size < 16) {
                DRM_ERROR("SPI transmit buffer too small: %zu\n", tx_size);
                return -EINVAL;
        }

        /*
         * Even though it's not the SPI device that does DMA (the master does),
         * the dma mask is necessary for the dma_alloc_wc() in
         * drm_gem_cma_create(). The dma_addr returned will be a physical
         * adddress which might be different from the bus address, but this is
         * not a problem since the address will not be used.
         * The virtual address is used in the transfer and the SPI core
         * re-maps it on the SPI master device using the DMA streaming API
         * (spi_map_buf()).
         */
        if (!dev->coherent_dma_mask) {
                ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(32));
                if (ret) {
                        dev_warn(dev, "Failed to set dma mask %d\n", ret);
                        return ret;
                }
        }

        mipi->spi = spi;
        mipi->read_commands = mipi_dbi_dcs_read_commands;

        if (dc) {
                mipi->command = mipi_dbi_typec3_command;
                mipi->dc = dc;
                if (tinydrm_machine_little_endian() &&
                    !tinydrm_spi_bpw_supported(spi, 16))
                        mipi->swap_bytes = true;
        } else {
                mipi->command = mipi_dbi_typec1_command;
                mipi->tx_buf9_len = tx_size;
                mipi->tx_buf9 = devm_kmalloc(dev, tx_size, GFP_KERNEL);
                if (!mipi->tx_buf9)
                        return -ENOMEM;
        }

        DRM_DEBUG_DRIVER("SPI speed: %uMHz\n", spi->max_speed_hz / 1000000);

        return 0;
}
EXPORT_SYMBOL(mipi_dbi_spi_init);

#endif /* CONFIG_SPI */

#ifdef CONFIG_DEBUG_FS

static ssize_t mipi_dbi_debugfs_command_write(struct file *file,
                                              const char __user *ubuf,
                                              size_t count, loff_t *ppos)
{
        struct seq_file *m = file->private_data;
        struct mipi_dbi *mipi = m->private;
        u8 val, cmd = 0, parameters[64];
        char *buf, *pos, *token;
        unsigned int i;
        int ret;

        buf = memdup_user_nul(ubuf, count);
        if (IS_ERR(buf))
                return PTR_ERR(buf);

        /* strip trailing whitespace */
        for (i = count - 1; i > 0; i--)
                if (isspace(buf[i]))
                        buf[i] = '\0';
                else
                        break;
        i = 0;
        pos = buf;
        while (pos) {
                token = strsep(&pos, " ");
                if (!token) {
                        ret = -EINVAL;
                        goto err_free;
                }

                ret = kstrtou8(token, 16, &val);
                if (ret < 0)
                        goto err_free;

                if (token == buf)
                        cmd = val;
                else
                        parameters[i++] = val;

                if (i == 64) {
                        ret = -E2BIG;
                        goto err_free;
                }
        }

        ret = mipi_dbi_command_buf(mipi, cmd, parameters, i);

err_free:
        kfree(buf);

        return ret < 0 ? ret : count;
}

static int mipi_dbi_debugfs_command_show(struct seq_file *m, void *unused)
{
        struct mipi_dbi *mipi = m->private;
        u8 cmd, val[4];
        size_t len;
        int ret;

        for (cmd = 0; cmd < 255; cmd++) {
                if (!mipi_dbi_command_is_read(mipi, cmd))
                        continue;

                switch (cmd) {
                case MIPI_DCS_READ_MEMORY_START:
                case MIPI_DCS_READ_MEMORY_CONTINUE:
                        len = 2;
                        break;
                case MIPI_DCS_GET_DISPLAY_ID:
                        len = 3;
                        break;
                case MIPI_DCS_GET_DISPLAY_STATUS:
                        len = 4;
                        break;
                default:
                        len = 1;
                        break;
                }

                seq_printf(m, "%02x: ", cmd);
                ret = mipi_dbi_command_buf(mipi, cmd, val, len);
                if (ret) {
                        seq_puts(m, "XX\n");
                        continue;
                }
                seq_printf(m, "%*phN\n", (int)len, val);
        }

        return 0;
}

static int mipi_dbi_debugfs_command_open(struct inode *inode,
                                         struct file *file)
{
        return single_open(file, mipi_dbi_debugfs_command_show,
                           inode->i_private);
}

static const struct file_operations mipi_dbi_debugfs_command_fops = {
        .owner = THIS_MODULE,
        .open = mipi_dbi_debugfs_command_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
        .write = mipi_dbi_debugfs_command_write,
};

static const struct drm_info_list mipi_dbi_debugfs_list[] = {
        { "fb",   drm_fb_cma_debugfs_show, 0 },
};

/**
 * mipi_dbi_debugfs_init - Create debugfs entries
 * @minor: DRM minor
 *
 * This function creates a 'command' debugfs file for sending commands to the
 * controller or getting the read command values.
 * Drivers can use this as their &drm_driver->debugfs_init callback.
 *
 * Returns:
 * Zero on success, negative error code on failure.
 */
int mipi_dbi_debugfs_init(struct drm_minor *minor)
{
        struct tinydrm_device *tdev = minor->dev->dev_private;
        struct mipi_dbi *mipi = mipi_dbi_from_tinydrm(tdev);
        umode_t mode = S_IFREG | S_IWUSR;

        if (mipi->read_commands)
                mode |= S_IRUGO;
        debugfs_create_file("command", mode, minor->debugfs_root, mipi,
                            &mipi_dbi_debugfs_command_fops);

        return drm_debugfs_create_files(mipi_dbi_debugfs_list,
                                        ARRAY_SIZE(mipi_dbi_debugfs_list),
                                        minor->debugfs_root, minor);
}
EXPORT_SYMBOL(mipi_dbi_debugfs_init);

#endif

MODULE_LICENSE("GPL");