// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for Sitronix ST7571, a 4 level gray scale dot matrix LCD controller
 *
 * Copyright (C) 2025 Marcus Folkesson <marcus.folkesson@gmail.com>
 */

#include <linux/bitfield.h>
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/regmap.h>

#include <drm/clients/drm_client_setup.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_connector.h>
#include <drm/drm_crtc_helper.h>
#include <drm/drm_damage_helper.h>
#include <drm/drm_drv.h>
#include <drm/drm_encoder.h>
#include <drm/drm_fb_helper.h>
#include <drm/drm_fbdev_shmem.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem_atomic_helper.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_gem_shmem_helper.h>
#include <drm/drm_modeset_helper_vtables.h>
#include <drm/drm_module.h>
#include <drm/drm_plane.h>
#include <drm/drm_probe_helper.h>

#include <video/display_timing.h>
#include <video/of_display_timing.h>

#include "st7571.h"

#define ST7571_COMMAND_MODE                     (0x00)
#define ST7571_DATA_MODE                        (0x40)

/* Normal mode command set */
#define ST7571_DISPLAY_OFF                      (0xae)
#define ST7571_DISPLAY_ON                       (0xaf)
#define ST7571_OSC_ON                           (0xab)
#define ST7571_SET_COLUMN_LSB(c)                (0x00 | FIELD_PREP(GENMASK(3, 0), (c)))
#define ST7571_SET_COLUMN_MSB(c)                (0x10 | FIELD_PREP(GENMASK(2, 0), (c) >> 4))
#define ST7571_SET_COM0_LSB(x)                  (FIELD_PREP(GENMASK(6, 0), (x)))
#define ST7571_SET_COM0_MSB                     (0x44)
#define ST7571_SET_COM_SCAN_DIR(d)              (0xc0 | FIELD_PREP(GENMASK(3, 3), (d)))
#define ST7571_SET_CONTRAST_LSB(c)              (FIELD_PREP(GENMASK(5, 0), (c)))
#define ST7571_SET_CONTRAST_MSB                 (0x81)
#define ST7571_SET_DISPLAY_DUTY_LSB(d)          (FIELD_PREP(GENMASK(7, 0), (d)))
#define ST7571_SET_DISPLAY_DUTY_MSB             (0x48)
#define ST7571_SET_ENTIRE_DISPLAY_ON(p)         (0xa4 | FIELD_PREP(GENMASK(0, 0), (p)))
#define ST7571_SET_LCD_BIAS(b)                  (0x50 | FIELD_PREP(GENMASK(2, 0), (b)))
#define ST7571_SET_MODE_LSB(m)                  (FIELD_PREP(GENMASK(7, 2), (m)))
#define ST7571_SET_MODE_MSB                     (0x38)
#define ST7571_SET_PAGE(p)                      (0xb0 | FIELD_PREP(GENMASK(3, 0), (p)))
#define ST7571_SET_POWER(p)                     (0x28 | FIELD_PREP(GENMASK(2, 0), (p)))
#define ST7571_SET_REGULATOR_REG(r)             (0x20 | FIELD_PREP(GENMASK(2, 0), (r)))
#define ST7571_SET_REVERSE(r)                   (0xa6 | FIELD_PREP(GENMASK(0, 0), (r)))
#define ST7571_SET_SEG_SCAN_DIR(d)              (0xa0 | FIELD_PREP(GENMASK(0, 0), (d)))
#define ST7571_SET_START_LINE_LSB(l)            (FIELD_PREP(GENMASK(6, 0), (l)))
#define ST7571_SET_START_LINE_MSB               (0x40)

/* Extension command set 3 */
#define ST7571_COMMAND_SET_3                    (0x7b)
#define ST7571_SET_COLOR_MODE(c)                (0x10 | FIELD_PREP(GENMASK(0, 0), (c)))
#define ST7571_COMMAND_SET_NORMAL               (0x00)

/* ST7567 commands */
#define ST7567_SET_LCD_BIAS(m) (0xa2 | FIELD_PREP(GENMASK(0, 0), (m)))

#define ST7571_PAGE_HEIGHT 8

#define DRIVER_NAME "st7571"
#define DRIVER_DESC "ST7571 DRM driver"
#define DRIVER_MAJOR 1
#define DRIVER_MINOR 0

static inline struct st7571_device *drm_to_st7571(struct drm_device *drm)
{
        return container_of(drm, struct st7571_device, drm);
}

static int st7571_send_command_list(struct st7571_device *st7571,
                                    const u8 *cmd_list, size_t len)
{
        int ret;

        for (int i = 0; i < len; i++) {
                ret = regmap_write(st7571->regmap, ST7571_COMMAND_MODE, cmd_list[i]);
                if (ret < 0)
                        return ret;
        }

        return ret;
}

static inline u8 st7571_transform_xy(const char *p, int x, int y, u8 bpp)
{
        int xrest = x % 8;
        u8 result = 0;
        u8 row_len = 16 * bpp;

        /*
         * Transforms an (x, y) pixel coordinate into a vertical 8-bit
         * column from the framebuffer. It calculates the corresponding byte in the
         * framebuffer, extracts the bit at the given x position across 8 consecutive
         * rows, and packs those bits into a single byte.
         *
         * Return an 8-bit value representing a vertical column of pixels.
         */
        x = x / 8;
        y = (y / 8) * 8;

        for (int i = 0; i < 8; i++) {
                int row_idx = y + i;
                u8 byte = p[row_idx * row_len + x];
                u8 bit = (byte >> xrest) & 1;

                result |= (bit << i);
        }

        return result;
}

static int st7571_set_position(struct st7571_device *st7571, int x, int y)
{
        u8 cmd_list[] = {
                ST7571_SET_COLUMN_LSB(x),
                ST7571_SET_COLUMN_MSB(x),
                ST7571_SET_PAGE(y / ST7571_PAGE_HEIGHT),
        };

        return st7571_send_command_list(st7571, cmd_list, ARRAY_SIZE(cmd_list));
}

static int st7571_fb_clear_screen(struct st7571_device *st7571)
{
        u32 npixels = st7571->ncols * round_up(st7571->nlines, ST7571_PAGE_HEIGHT) * st7571->bpp;
        char pixelvalue = 0x00;

        st7571_set_position(st7571, 0, 0);
        for (int i = 0; i < npixels; i++)
                regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, &pixelvalue, 1);

        return 0;
}

static void st7571_prepare_buffer_monochrome(struct st7571_device *st7571,
                                             const struct iosys_map *vmap,
                                             struct drm_framebuffer *fb,
                                             struct drm_rect *rect,
                                             struct drm_format_conv_state *fmtcnv_state)
{
        unsigned int dst_pitch;
        struct iosys_map dst;
        u32 size;

        switch (fb->format->format) {
        case DRM_FORMAT_XRGB8888:
                dst_pitch = DIV_ROUND_UP(drm_rect_width(rect), 8);
                iosys_map_set_vaddr(&dst, st7571->hwbuf);

                drm_fb_xrgb8888_to_mono(&dst, &dst_pitch, vmap, fb, rect, fmtcnv_state);
                break;

        case DRM_FORMAT_R1:
                size = (rect->x2 - rect->x1) * (rect->y2 - rect->y1) / 8;
                memcpy(st7571->hwbuf, vmap->vaddr, size);
                break;
        }
}

static void st7571_prepare_buffer_grayscale(struct st7571_device *st7571,
                                            const struct iosys_map *vmap,
                                            struct drm_framebuffer *fb,
                                            struct drm_rect *rect,
                                            struct drm_format_conv_state *fmtcnv_state)
{
        u32 size = (rect->x2 - rect->x1) * (rect->y2 - rect->y1) / 8;
        unsigned int dst_pitch;
        struct iosys_map dst;

        switch (fb->format->format) {
        case DRM_FORMAT_XRGB8888:
                dst_pitch = DIV_ROUND_UP(drm_rect_width(rect), 4);
                iosys_map_set_vaddr(&dst, st7571->hwbuf);

                drm_fb_xrgb8888_to_gray2(&dst, &dst_pitch, vmap, fb, rect, fmtcnv_state);
                break;

        case DRM_FORMAT_R1:
                size = (rect->x2 - rect->x1) * (rect->y2 - rect->y1) / 8;
                memcpy(st7571->hwbuf, vmap->vaddr, size);
                break;

        case DRM_FORMAT_R2:
                size = (rect->x2 - rect->x1) * (rect->y2 - rect->y1) / 4;
                memcpy(st7571->hwbuf, vmap->vaddr, size);
                break;
        }
}

static int st7571_fb_update_rect_monochrome(struct drm_framebuffer *fb, struct drm_rect *rect)
{
        struct st7571_device *st7571 = drm_to_st7571(fb->dev);
        char *row = st7571->row;

        /* Align y to display page boundaries */
        rect->y1 = round_down(rect->y1, ST7571_PAGE_HEIGHT);
        rect->y2 = min_t(unsigned int, round_up(rect->y2, ST7571_PAGE_HEIGHT), st7571->nlines);

        for (int y = rect->y1; y < rect->y2; y += ST7571_PAGE_HEIGHT) {
                for (int x = rect->x1; x < rect->x2; x++)
                        row[x] = st7571_transform_xy(st7571->hwbuf, x, y, 1);

                st7571_set_position(st7571, rect->x1, y);

                /* TODO: Investige why we can't write multiple bytes at once */
                for (int x = rect->x1; x < rect->x2; x++)
                        regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, row + x, 1);
        }

        return 0;
}

static int st7571_fb_update_rect_grayscale(struct drm_framebuffer *fb, struct drm_rect *rect)
{
        struct st7571_device *st7571 = drm_to_st7571(fb->dev);
        u32 format = fb->format->format;
        char *row = st7571->row;
        int x1;
        int x2;

        /* Align y to display page boundaries */
        rect->y1 = round_down(rect->y1, ST7571_PAGE_HEIGHT);
        rect->y2 = min_t(unsigned int, round_up(rect->y2, ST7571_PAGE_HEIGHT), st7571->nlines);

        switch (format) {
        case DRM_FORMAT_R1:
                x1 = rect->x1 * 1;
                x2 = rect->x2 * 1;
                break;
        case DRM_FORMAT_R2:
                fallthrough;
        case DRM_FORMAT_XRGB8888:
                x1 = rect->x1 * 2;
                x2 = rect->x2 * 2;
                break;
        }

        for (int y = rect->y1; y < rect->y2; y += ST7571_PAGE_HEIGHT) {
                for (int x = x1; x < x2; x++)
                        row[x] = st7571_transform_xy(st7571->hwbuf, x, y, 2);

                st7571_set_position(st7571, rect->x1, y);

                /* TODO: Investige why we can't write multiple bytes at once */
                for (int x = x1; x < x2; x++) {
                        regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, row + x, 1);

                        /*
                         * As the display supports grayscale, all pixels must be written as two bits
                         * even if the format is monochrome.
                         *
                         * The bit values maps to the following grayscale:
                         * 0 0 = Black
                         * 0 1 = Dark gray
                         * 1 0 = Light gray
                         * 1 1 = White
                         *
                         * For monochrome formats, write the same value twice to get
                         * either a black or white pixel.
                         */
                        if (format == DRM_FORMAT_R1)
                                regmap_bulk_write(st7571->regmap, ST7571_DATA_MODE, row + x, 1);
                }
        }

        return 0;
}

static int st7571_connector_get_modes(struct drm_connector *conn)
{
        struct st7571_device *st7571 = drm_to_st7571(conn->dev);

        return drm_connector_helper_get_modes_fixed(conn, &st7571->mode);
}

static const struct drm_connector_helper_funcs st7571_connector_helper_funcs = {
        .get_modes = st7571_connector_get_modes,
};

static const struct st7571_panel_format st7571_monochrome = {
        .prepare_buffer = st7571_prepare_buffer_monochrome,
        .update_rect = st7571_fb_update_rect_monochrome,
        .mode = ST7571_COLOR_MODE_BLACKWHITE,
        .formats = {
                DRM_FORMAT_XRGB8888,
                DRM_FORMAT_R1,
        },
        .nformats = 2,
};

static const struct st7571_panel_format st7571_grayscale = {
        .prepare_buffer = st7571_prepare_buffer_grayscale,
        .update_rect = st7571_fb_update_rect_grayscale,
        .mode = ST7571_COLOR_MODE_GRAY,
        .formats = {
                DRM_FORMAT_XRGB8888,
                DRM_FORMAT_R1,
                DRM_FORMAT_R2,
        },
        .nformats = 3,
};

static const u64 st7571_primary_plane_fmtmods[] = {
        DRM_FORMAT_MOD_LINEAR,
        DRM_FORMAT_MOD_INVALID
};

static int st7571_primary_plane_helper_atomic_check(struct drm_plane *plane,
                                                    struct drm_atomic_state *state)
{
        struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(state, plane);
        struct drm_crtc *new_crtc = new_plane_state->crtc;
        struct drm_crtc_state *new_crtc_state = NULL;

        if (new_crtc)
                new_crtc_state = drm_atomic_get_new_crtc_state(state, new_crtc);

        return drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
                                                   DRM_PLANE_NO_SCALING,
                                                   DRM_PLANE_NO_SCALING,
                                                   false, false);
}

static void st7571_primary_plane_helper_atomic_update(struct drm_plane *plane,
                                                      struct drm_atomic_state *state)
{
        struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(state, plane);
        struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
        struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
        struct drm_framebuffer *fb = plane_state->fb;
        struct drm_atomic_helper_damage_iter iter;
        struct drm_device *drm = plane->dev;
        struct drm_rect damage;
        struct st7571_device *st7571 = drm_to_st7571(plane->dev);
        int ret, idx;

        if (!fb)
                return; /* no framebuffer; plane is disabled */

        ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
        if (ret)
                return;

        if (!drm_dev_enter(drm, &idx))
                goto out_drm_gem_fb_end_cpu_access;

        drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
        drm_atomic_for_each_plane_damage(&iter, &damage) {
                st7571->pformat->prepare_buffer(st7571,
                                                &shadow_plane_state->data[0],
                                                fb, &damage,
                                                &shadow_plane_state->fmtcnv_state);

                st7571->pformat->update_rect(fb, &damage);
        }

        drm_dev_exit(idx);

out_drm_gem_fb_end_cpu_access:
        drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
}

static void st7571_primary_plane_helper_atomic_disable(struct drm_plane *plane,
                                                       struct drm_atomic_state *state)
{
        struct drm_device *drm = plane->dev;
        struct st7571_device *st7571 = drm_to_st7571(plane->dev);
        int idx;

        if (!drm_dev_enter(drm, &idx))
                return;

        st7571_fb_clear_screen(st7571);
        drm_dev_exit(idx);
}

static const struct drm_plane_helper_funcs st7571_primary_plane_helper_funcs = {
        DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
        .atomic_check = st7571_primary_plane_helper_atomic_check,
        .atomic_update = st7571_primary_plane_helper_atomic_update,
        .atomic_disable = st7571_primary_plane_helper_atomic_disable,
};

static const struct drm_plane_funcs st7571_primary_plane_funcs = {
        .update_plane = drm_atomic_helper_update_plane,
        .disable_plane = drm_atomic_helper_disable_plane,
        .destroy = drm_plane_cleanup,
        DRM_GEM_SHADOW_PLANE_FUNCS,
};

/*
 * CRTC
 */

static enum drm_mode_status st7571_crtc_mode_valid(struct drm_crtc *crtc,
                                                   const struct drm_display_mode *mode)
{
        struct st7571_device *st7571 = drm_to_st7571(crtc->dev);

        return drm_crtc_helper_mode_valid_fixed(crtc, mode, &st7571->mode);
}

static const struct drm_crtc_helper_funcs st7571_crtc_helper_funcs = {
        .atomic_check = drm_crtc_helper_atomic_check,
        .mode_valid = st7571_crtc_mode_valid,
};

static const struct drm_crtc_funcs st7571_crtc_funcs = {
        .reset = drm_atomic_helper_crtc_reset,
        .destroy = drm_crtc_cleanup,
        .set_config = drm_atomic_helper_set_config,
        .page_flip = drm_atomic_helper_page_flip,
        .atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
        .atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
};

/*
 * Encoder
 */

static void st7571_encoder_atomic_enable(struct drm_encoder *encoder,
                                         struct drm_atomic_state *state)
{
        struct drm_device *drm = encoder->dev;
        struct st7571_device *st7571 = drm_to_st7571(drm);
        u8 command = ST7571_DISPLAY_ON;
        int ret;

        ret = st7571->pdata->init(st7571);
        if (ret)
                return;

        st7571_send_command_list(st7571, &command, 1);
}

static void st7571_encoder_atomic_disable(struct drm_encoder *encoder,
                                          struct drm_atomic_state *state)
{
        struct drm_device *drm = encoder->dev;
        struct st7571_device *st7571 = drm_to_st7571(drm);
        u8 command = ST7571_DISPLAY_OFF;

        st7571_send_command_list(st7571, &command, 1);
}

static const struct drm_encoder_funcs st7571_encoder_funcs = {
        .destroy = drm_encoder_cleanup,

};

static const struct drm_encoder_helper_funcs st7571_encoder_helper_funcs = {
        .atomic_enable = st7571_encoder_atomic_enable,
        .atomic_disable = st7571_encoder_atomic_disable,
};

/*
 * Connector
 */

static const struct drm_connector_funcs st7571_connector_funcs = {
        .reset = drm_atomic_helper_connector_reset,
        .fill_modes = drm_helper_probe_single_connector_modes,
        .destroy = drm_connector_cleanup,
        .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
        .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
};

static const struct drm_mode_config_funcs st7571_mode_config_funcs = {
        .fb_create = drm_gem_fb_create_with_dirty,
        .atomic_check = drm_atomic_helper_check,
        .atomic_commit = drm_atomic_helper_commit,
};

static struct drm_display_mode st7571_mode(struct st7571_device *st7571)
{
        struct drm_display_mode mode = {
                DRM_SIMPLE_MODE(st7571->ncols, st7571->nlines,
                                st7571->width_mm, st7571->height_mm),
        };

        return mode;
}

static int st7571_mode_config_init(struct st7571_device *st7571)
{
        struct drm_device *drm = &st7571->drm;
        const struct st7571_panel_constraints *constraints = &st7571->pdata->constraints;
        int ret;

        ret = drmm_mode_config_init(drm);
        if (ret)
                return ret;

        drm->mode_config.min_width = constraints->min_ncols;
        drm->mode_config.min_height = constraints->min_nlines;
        drm->mode_config.max_width = constraints->max_ncols;
        drm->mode_config.max_height = constraints->max_nlines;
        drm->mode_config.preferred_depth = 24;
        drm->mode_config.funcs = &st7571_mode_config_funcs;

        return 0;
}

static int st7571_plane_init(struct st7571_device *st7571,
                             const struct st7571_panel_format *pformat)
{
        struct drm_plane *primary_plane = &st7571->primary_plane;
        struct drm_device *drm = &st7571->drm;
        int ret;

        ret = drm_universal_plane_init(drm, primary_plane, 0,
                                       &st7571_primary_plane_funcs,
                                       pformat->formats,
                                       pformat->nformats,
                                       st7571_primary_plane_fmtmods,
                                       DRM_PLANE_TYPE_PRIMARY, NULL);
        if (ret)
                return ret;

        drm_plane_helper_add(primary_plane, &st7571_primary_plane_helper_funcs);
        drm_plane_enable_fb_damage_clips(primary_plane);

        return 0;
}

static int st7571_crtc_init(struct st7571_device *st7571)
{
        struct drm_plane *primary_plane = &st7571->primary_plane;
        struct drm_crtc *crtc = &st7571->crtc;
        struct drm_device *drm = &st7571->drm;
        int ret;

        ret = drm_crtc_init_with_planes(drm, crtc, primary_plane, NULL,
                                        &st7571_crtc_funcs, NULL);
        if (ret)
                return ret;

        drm_crtc_helper_add(crtc, &st7571_crtc_helper_funcs);

        return 0;
}

static int st7571_encoder_init(struct st7571_device *st7571)
{
        struct drm_encoder *encoder = &st7571->encoder;
        struct drm_crtc *crtc = &st7571->crtc;
        struct drm_device *drm = &st7571->drm;
        int ret;

        ret = drm_encoder_init(drm, encoder, &st7571_encoder_funcs, DRM_MODE_ENCODER_NONE, NULL);
        if (ret)
                return ret;

        drm_encoder_helper_add(encoder, &st7571_encoder_helper_funcs);

        encoder->possible_crtcs = drm_crtc_mask(crtc);

        return 0;
}

static int st7571_connector_init(struct st7571_device *st7571)
{
        struct drm_connector *connector = &st7571->connector;
        struct drm_encoder *encoder = &st7571->encoder;
        struct drm_device *drm = &st7571->drm;
        int ret;

        ret = drm_connector_init(drm, connector, &st7571_connector_funcs,
                                 DRM_MODE_CONNECTOR_Unknown);
        if (ret)
                return ret;

        drm_connector_helper_add(connector, &st7571_connector_helper_funcs);

        return drm_connector_attach_encoder(connector, encoder);
}

DEFINE_DRM_GEM_FOPS(st7571_fops);

static const struct drm_driver st7571_driver = {
        .driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC,

        .name            = DRIVER_NAME,
        .desc            = DRIVER_DESC,
        .major           = DRIVER_MAJOR,
        .minor           = DRIVER_MINOR,

        .fops            = &st7571_fops,
        DRM_GEM_SHMEM_DRIVER_OPS,
        DRM_FBDEV_SHMEM_DRIVER_OPS,
};

static int st7571_validate_parameters(struct st7571_device *st7571)
{
        struct device *dev = st7571->dev;
        const struct st7571_panel_constraints *constraints = &st7571->pdata->constraints;

        if (st7571->width_mm  == 0) {
                dev_err(dev, "Invalid panel width\n");
                return -EINVAL;
        }

        if (st7571->height_mm == 0) {
                dev_err(dev, "Invalid panel height\n");
                return -EINVAL;
        }

        if (st7571->nlines < constraints->min_nlines ||
            st7571->nlines > constraints->max_nlines) {
                dev_err(dev, "Invalid timing configuration.\n");
                return -EINVAL;
        }

        if (st7571->startline + st7571->nlines > constraints->max_nlines) {
                dev_err(dev, "Invalid timing configuration.\n");
                return -EINVAL;
        }

        if (st7571->ncols < constraints->min_ncols ||
            st7571->ncols > constraints->max_ncols) {
                dev_err(dev, "Invalid timing configuration.\n");
                return -EINVAL;
        }

        if (st7571->grayscale && !constraints->support_grayscale) {
                dev_err(dev, "Grayscale not supported\n");
                return -EINVAL;
        }

        return 0;
}

static int st7567_parse_dt(struct st7571_device *st7567)
{
        struct device *dev = st7567->dev;
        struct device_node *np = dev->of_node;
        struct display_timing dt;
        int ret;

        ret = of_get_display_timing(np, "panel-timing", &dt);
        if (ret) {
                dev_err(dev, "Failed to get display timing from DT\n");
                return ret;
        }

        of_property_read_u32(np, "width-mm", &st7567->width_mm);
        of_property_read_u32(np, "height-mm", &st7567->height_mm);
        st7567->inverted = of_property_read_bool(np, "sitronix,inverted");

        st7567->pformat = &st7571_monochrome;
        st7567->bpp = 1;

        st7567->startline = dt.vfront_porch.typ;
        st7567->nlines = dt.vactive.typ;
        st7567->ncols = dt.hactive.typ;

        return 0;
}

static int st7571_parse_dt(struct st7571_device *st7571)
{
        struct device *dev = st7571->dev;
        struct device_node *np = dev->of_node;
        struct display_timing dt;
        int ret;

        ret = of_get_display_timing(np, "panel-timing", &dt);
        if (ret) {
                dev_err(dev, "Failed to get display timing from DT\n");
                return ret;
        }

        of_property_read_u32(np, "width-mm", &st7571->width_mm);
        of_property_read_u32(np, "height-mm", &st7571->height_mm);
        st7571->grayscale = of_property_read_bool(np, "sitronix,grayscale");
        st7571->inverted = of_property_read_bool(np, "sitronix,inverted");

        if (st7571->grayscale) {
                st7571->pformat = &st7571_grayscale;
                st7571->bpp = 2;
        } else {
                st7571->pformat = &st7571_monochrome;
                st7571->bpp = 1;
        }

        st7571->startline = dt.vfront_porch.typ;
        st7571->nlines = dt.vactive.typ;
        st7571->ncols = dt.hactive.typ;

        st7571->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
        if (IS_ERR(st7571->reset))
                return dev_err_probe(dev, PTR_ERR(st7571->reset),
                                     "Failed to get reset gpio\n");

        return 0;
}

static void st7571_reset(struct st7571_device *st7571)
{
        gpiod_set_value_cansleep(st7571->reset, 1);
        fsleep(20);
        gpiod_set_value_cansleep(st7571->reset, 0);
}

static int st7567_lcd_init(struct st7571_device *st7567)
{
        /*
         * Most of the initialization sequence is taken directly from the
         * referential initial code in the ST7567 datasheet.
         */
        u8 commands[] = {
                ST7571_DISPLAY_OFF,

                ST7567_SET_LCD_BIAS(1),

                ST7571_SET_SEG_SCAN_DIR(0),
                ST7571_SET_COM_SCAN_DIR(1),

                ST7571_SET_REGULATOR_REG(4),
                ST7571_SET_CONTRAST_MSB,
                ST7571_SET_CONTRAST_LSB(0x20),

                ST7571_SET_START_LINE_MSB,
                ST7571_SET_START_LINE_LSB(st7567->startline),

                ST7571_SET_POWER(0x4),  /* Power Control, VC: ON, VR: OFF, VF: OFF */
                ST7571_SET_POWER(0x6),  /* Power Control, VC: ON, VR: ON, VF: OFF */
                ST7571_SET_POWER(0x7),  /* Power Control, VC: ON, VR: ON, VF: ON */

                ST7571_SET_REVERSE(st7567->inverted ? 1 : 0),
                ST7571_SET_ENTIRE_DISPLAY_ON(0),
        };

        return st7571_send_command_list(st7567, commands, ARRAY_SIZE(commands));
}

static int st7571_lcd_init(struct st7571_device *st7571)
{
        /*
         * Most of the initialization sequence is taken directly from the
         * referential initial code in the ST7571 datasheet.
         */
        u8 commands[] = {
                ST7571_DISPLAY_OFF,

                ST7571_SET_MODE_MSB,
                ST7571_SET_MODE_LSB(0x2e),

                ST7571_SET_SEG_SCAN_DIR(0),
                ST7571_SET_COM_SCAN_DIR(1),

                ST7571_SET_COM0_MSB,
                ST7571_SET_COM0_LSB(0x00),

                ST7571_SET_START_LINE_MSB,
                ST7571_SET_START_LINE_LSB(st7571->startline),

                ST7571_OSC_ON,
                ST7571_SET_REGULATOR_REG(5),
                ST7571_SET_CONTRAST_MSB,
                ST7571_SET_CONTRAST_LSB(0x33),
                ST7571_SET_LCD_BIAS(0x04),
                ST7571_SET_DISPLAY_DUTY_MSB,
                ST7571_SET_DISPLAY_DUTY_LSB(st7571->nlines),

                ST7571_SET_POWER(0x4),  /* Power Control, VC: ON, VR: OFF, VF: OFF */
                ST7571_SET_POWER(0x6),  /* Power Control, VC: ON, VR: ON, VF: OFF */
                ST7571_SET_POWER(0x7),  /* Power Control, VC: ON, VR: ON, VF: ON */

                ST7571_COMMAND_SET_3,
                ST7571_SET_COLOR_MODE(st7571->pformat->mode),
                ST7571_COMMAND_SET_NORMAL,

                ST7571_SET_REVERSE(st7571->inverted ? 1 : 0),
                ST7571_SET_ENTIRE_DISPLAY_ON(0),
        };

        /* Perform a reset before initializing the controller */
        st7571_reset(st7571);

        return st7571_send_command_list(st7571, commands, ARRAY_SIZE(commands));
}

struct st7571_device *st7571_probe(struct device *dev,
                                   struct regmap *regmap)
{
        struct st7571_device *st7571;
        struct drm_device *drm;
        int ret;

        st7571 = devm_drm_dev_alloc(dev, &st7571_driver,
                                    struct st7571_device, drm);
        if (IS_ERR(st7571))
                return st7571;

        drm = &st7571->drm;
        st7571->dev = dev;
        st7571->pdata = device_get_match_data(st7571->dev);

        ret = st7571->pdata->parse_dt(st7571);
        if (ret)
                return ERR_PTR(ret);

        ret = st7571_validate_parameters(st7571);
        if (ret)
                return ERR_PTR(ret);

        st7571->mode = st7571_mode(st7571);
        st7571->regmap = regmap;

        st7571->hwbuf = devm_kzalloc(st7571->dev,
                                     (st7571->nlines * st7571->ncols * st7571->bpp) / 8,
                                     GFP_KERNEL);
        if (!st7571->hwbuf)
                return ERR_PTR(-ENOMEM);

        st7571->row = devm_kzalloc(st7571->dev,
                                   (st7571->ncols * st7571->bpp),
                                   GFP_KERNEL);
        if (!st7571->row)
                return ERR_PTR(-ENOMEM);

        ret = st7571_mode_config_init(st7571);
        if (ret) {
                dev_err(st7571->dev, "Failed to initialize mode config\n");
                return ERR_PTR(ret);
        }

        ret = st7571_plane_init(st7571, st7571->pformat);
        if (ret) {
                dev_err(st7571->dev, "Failed to initialize primary plane\n");
                return ERR_PTR(ret);
        }

        ret = st7571_crtc_init(st7571);
        if (ret < 0) {
                dev_err(st7571->dev, "Failed to initialize CRTC\n");
                return ERR_PTR(ret);
        }

        ret = st7571_encoder_init(st7571);
        if (ret < 0) {
                dev_err(st7571->dev, "Failed to initialize encoder\n");
                return ERR_PTR(ret);
        }

        ret = st7571_connector_init(st7571);
        if (ret < 0) {
                dev_err(st7571->dev, "Failed to initialize connector\n");
                return ERR_PTR(ret);
        }

        drm_mode_config_reset(drm);

        ret = drm_dev_register(drm, 0);
        if (ret) {
                dev_err(st7571->dev, "Failed to register DRM device\n");
                return ERR_PTR(ret);
        }

        drm_client_setup(drm, NULL);
        return st7571;
}
EXPORT_SYMBOL_GPL(st7571_probe);

void st7571_remove(struct st7571_device *st7571)
{
        drm_dev_unplug(&st7571->drm);
}
EXPORT_SYMBOL_GPL(st7571_remove);

const struct st7571_panel_data st7567_config = {
        .init = st7567_lcd_init,
        .parse_dt = st7567_parse_dt,
        .constraints = {
                .min_nlines = 1,
                .max_nlines = 64,
                .min_ncols = 128,
                .max_ncols = 128,
                .support_grayscale = false,
        },
};
EXPORT_SYMBOL_NS_GPL(st7567_config, "DRM_ST7571");

const struct st7571_panel_data st7571_config = {
        .init = st7571_lcd_init,
        .parse_dt = st7571_parse_dt,
        .constraints = {
                .min_nlines = 1,
                .max_nlines = 128,
                .min_ncols = 128,
                .max_ncols = 128,
                .support_grayscale = true,
        },
};
EXPORT_SYMBOL_NS_GPL(st7571_config, "DRM_ST7571");

MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@gmail.com>");
MODULE_DESCRIPTION("DRM Driver for Sitronix ST7571 LCD controller");
MODULE_LICENSE("GPL");