// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * DRM driver for Pervasive Displays RePaper branded e-ink panels
 *
 * Copyright 2013-2017 Pervasive Displays, Inc.
 * Copyright 2017 Noralf Trønnes
 *
 * The driver supports:
 * Material Film: Aurora Mb (V231)
 * Driver IC: G2 (eTC)
 *
 * The controller code was taken from the userspace driver:
 * https://github.com/repaper/gratis
 */

#include <linux/delay.h>
#include <linux/dma-buf.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/property.h>
#include <linux/sched/clock.h>
#include <linux/spi/spi.h>
#include <linux/thermal.h>

#include <drm/drm_atomic_helper.h>
#include <drm/drm_connector.h>
#include <drm/drm_damage_helper.h>
#include <drm/drm_drv.h>
#include <drm/drm_fb_cma_helper.h>
#include <drm/drm_fb_helper.h>
#include <drm/drm_format_helper.h>
#include <drm/drm_gem_cma_helper.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_managed.h>
#include <drm/drm_modes.h>
#include <drm/drm_rect.h>
#include <drm/drm_probe_helper.h>
#include <drm/drm_simple_kms_helper.h>

#define REPAPER_RID_G2_COG_ID   0x12

enum repaper_model {
        /* 0 is reserved to avoid clashing with NULL */
        E1144CS021 = 1,
        E1190CS021,
        E2200CS021,
        E2271CS021,
};

enum repaper_stage {         /* Image pixel -> Display pixel */
        REPAPER_COMPENSATE,  /* B -> W, W -> B (Current Image) */
        REPAPER_WHITE,       /* B -> N, W -> W (Current Image) */
        REPAPER_INVERSE,     /* B -> N, W -> B (New Image) */
        REPAPER_NORMAL       /* B -> B, W -> W (New Image) */
};

enum repaper_epd_border_byte {
        REPAPER_BORDER_BYTE_NONE,
        REPAPER_BORDER_BYTE_ZERO,
        REPAPER_BORDER_BYTE_SET,
};

struct repaper_epd {
        struct drm_device drm;
        struct drm_simple_display_pipe pipe;
        const struct drm_display_mode *mode;
        struct drm_connector connector;
        struct spi_device *spi;

        struct gpio_desc *panel_on;
        struct gpio_desc *border;
        struct gpio_desc *discharge;
        struct gpio_desc *reset;
        struct gpio_desc *busy;

        struct thermal_zone_device *thermal;

        unsigned int height;
        unsigned int width;
        unsigned int bytes_per_scan;
        const u8 *channel_select;
        unsigned int stage_time;
        unsigned int factored_stage_time;
        bool middle_scan;
        bool pre_border_byte;
        enum repaper_epd_border_byte border_byte;

        u8 *line_buffer;
        void *current_frame;

        bool cleared;
        bool partial;
};

static inline struct repaper_epd *drm_to_epd(struct drm_device *drm)
{
        return container_of(drm, struct repaper_epd, drm);
}

static int repaper_spi_transfer(struct spi_device *spi, u8 header,
                                const void *tx, void *rx, size_t len)
{
        void *txbuf = NULL, *rxbuf = NULL;
        struct spi_transfer tr[2] = {};
        u8 *headerbuf;
        int ret;

        headerbuf = kmalloc(1, GFP_KERNEL);
        if (!headerbuf)
                return -ENOMEM;

        headerbuf[0] = header;
        tr[0].tx_buf = headerbuf;
        tr[0].len = 1;

        /* Stack allocated tx? */
        if (tx && len <= 32) {
                txbuf = kmemdup(tx, len, GFP_KERNEL);
                if (!txbuf) {
                        ret = -ENOMEM;
                        goto out_free;
                }
        }

        if (rx) {
                rxbuf = kmalloc(len, GFP_KERNEL);
                if (!rxbuf) {
                        ret = -ENOMEM;
                        goto out_free;
                }
        }

        tr[1].tx_buf = txbuf ? txbuf : tx;
        tr[1].rx_buf = rxbuf;
        tr[1].len = len;

        ndelay(80);
        ret = spi_sync_transfer(spi, tr, 2);
        if (rx && !ret)
                memcpy(rx, rxbuf, len);

out_free:
        kfree(headerbuf);
        kfree(txbuf);
        kfree(rxbuf);

        return ret;
}

static int repaper_write_buf(struct spi_device *spi, u8 reg,
                             const u8 *buf, size_t len)
{
        int ret;

        ret = repaper_spi_transfer(spi, 0x70, &reg, NULL, 1);
        if (ret)
                return ret;

        return repaper_spi_transfer(spi, 0x72, buf, NULL, len);
}

static int repaper_write_val(struct spi_device *spi, u8 reg, u8 val)
{
        return repaper_write_buf(spi, reg, &val, 1);
}

static int repaper_read_val(struct spi_device *spi, u8 reg)
{
        int ret;
        u8 val;

        ret = repaper_spi_transfer(spi, 0x70, &reg, NULL, 1);
        if (ret)
                return ret;

        ret = repaper_spi_transfer(spi, 0x73, NULL, &val, 1);

        return ret ? ret : val;
}

static int repaper_read_id(struct spi_device *spi)
{
        int ret;
        u8 id;

        ret = repaper_spi_transfer(spi, 0x71, NULL, &id, 1);

        return ret ? ret : id;
}

static void repaper_spi_mosi_low(struct spi_device *spi)
{
        const u8 buf[1] = { 0 };

        spi_write(spi, buf, 1);
}

/* pixels on display are numbered from 1 so even is actually bits 1,3,5,... */
static void repaper_even_pixels(struct repaper_epd *epd, u8 **pp,
                                const u8 *data, u8 fixed_value, const u8 *mask,
                                enum repaper_stage stage)
{
        unsigned int b;

        for (b = 0; b < (epd->width / 8); b++) {
                if (data) {
                        u8 pixels = data[b] & 0xaa;
                        u8 pixel_mask = 0xff;
                        u8 p1, p2, p3, p4;

                        if (mask) {
                                pixel_mask = (mask[b] ^ pixels) & 0xaa;
                                pixel_mask |= pixel_mask >> 1;
                        }

                        switch (stage) {
                        case REPAPER_COMPENSATE: /* B -> W, W -> B (Current) */
                                pixels = 0xaa | ((pixels ^ 0xaa) >> 1);
                                break;
                        case REPAPER_WHITE:      /* B -> N, W -> W (Current) */
                                pixels = 0x55 + ((pixels ^ 0xaa) >> 1);
                                break;
                        case REPAPER_INVERSE:    /* B -> N, W -> B (New) */
                                pixels = 0x55 | (pixels ^ 0xaa);
                                break;
                        case REPAPER_NORMAL:     /* B -> B, W -> W (New) */
                                pixels = 0xaa | (pixels >> 1);
                                break;
                        }

                        pixels = (pixels & pixel_mask) | (~pixel_mask & 0x55);
                        p1 = (pixels >> 6) & 0x03;
                        p2 = (pixels >> 4) & 0x03;
                        p3 = (pixels >> 2) & 0x03;
                        p4 = (pixels >> 0) & 0x03;
                        pixels = (p1 << 0) | (p2 << 2) | (p3 << 4) | (p4 << 6);
                        *(*pp)++ = pixels;
                } else {
                        *(*pp)++ = fixed_value;
                }
        }
}

/* pixels on display are numbered from 1 so odd is actually bits 0,2,4,... */
static void repaper_odd_pixels(struct repaper_epd *epd, u8 **pp,
                               const u8 *data, u8 fixed_value, const u8 *mask,
                               enum repaper_stage stage)
{
        unsigned int b;

        for (b = epd->width / 8; b > 0; b--) {
                if (data) {
                        u8 pixels = data[b - 1] & 0x55;
                        u8 pixel_mask = 0xff;

                        if (mask) {
                                pixel_mask = (mask[b - 1] ^ pixels) & 0x55;
                                pixel_mask |= pixel_mask << 1;
                        }

                        switch (stage) {
                        case REPAPER_COMPENSATE: /* B -> W, W -> B (Current) */
                                pixels = 0xaa | (pixels ^ 0x55);
                                break;
                        case REPAPER_WHITE:      /* B -> N, W -> W (Current) */
                                pixels = 0x55 + (pixels ^ 0x55);
                                break;
                        case REPAPER_INVERSE:    /* B -> N, W -> B (New) */
                                pixels = 0x55 | ((pixels ^ 0x55) << 1);
                                break;
                        case REPAPER_NORMAL:     /* B -> B, W -> W (New) */
                                pixels = 0xaa | pixels;
                                break;
                        }

                        pixels = (pixels & pixel_mask) | (~pixel_mask & 0x55);
                        *(*pp)++ = pixels;
                } else {
                        *(*pp)++ = fixed_value;
                }
        }
}

/* interleave bits: (byte)76543210 -> (16 bit).7.6.5.4.3.2.1 */
static inline u16 repaper_interleave_bits(u16 value)
{
        value = (value | (value << 4)) & 0x0f0f;
        value = (value | (value << 2)) & 0x3333;
        value = (value | (value << 1)) & 0x5555;

        return value;
}

/* pixels on display are numbered from 1 */
static void repaper_all_pixels(struct repaper_epd *epd, u8 **pp,
                               const u8 *data, u8 fixed_value, const u8 *mask,
                               enum repaper_stage stage)
{
        unsigned int b;

        for (b = epd->width / 8; b > 0; b--) {
                if (data) {
                        u16 pixels = repaper_interleave_bits(data[b - 1]);
                        u16 pixel_mask = 0xffff;

                        if (mask) {
                                pixel_mask = repaper_interleave_bits(mask[b - 1]);

                                pixel_mask = (pixel_mask ^ pixels) & 0x5555;
                                pixel_mask |= pixel_mask << 1;
                        }

                        switch (stage) {
                        case REPAPER_COMPENSATE: /* B -> W, W -> B (Current) */
                                pixels = 0xaaaa | (pixels ^ 0x5555);
                                break;
                        case REPAPER_WHITE:      /* B -> N, W -> W (Current) */
                                pixels = 0x5555 + (pixels ^ 0x5555);
                                break;
                        case REPAPER_INVERSE:    /* B -> N, W -> B (New) */
                                pixels = 0x5555 | ((pixels ^ 0x5555) << 1);
                                break;
                        case REPAPER_NORMAL:     /* B -> B, W -> W (New) */
                                pixels = 0xaaaa | pixels;
                                break;
                        }

                        pixels = (pixels & pixel_mask) | (~pixel_mask & 0x5555);
                        *(*pp)++ = pixels >> 8;
                        *(*pp)++ = pixels;
                } else {
                        *(*pp)++ = fixed_value;
                        *(*pp)++ = fixed_value;
                }
        }
}

/* output one line of scan and data bytes to the display */
static void repaper_one_line(struct repaper_epd *epd, unsigned int line,
                             const u8 *data, u8 fixed_value, const u8 *mask,
                             enum repaper_stage stage)
{
        u8 *p = epd->line_buffer;
        unsigned int b;

        repaper_spi_mosi_low(epd->spi);

        if (epd->pre_border_byte)
                *p++ = 0x00;

        if (epd->middle_scan) {
                /* data bytes */
                repaper_odd_pixels(epd, &p, data, fixed_value, mask, stage);

                /* scan line */
                for (b = epd->bytes_per_scan; b > 0; b--) {
                        if (line / 4 == b - 1)
                                *p++ = 0x03 << (2 * (line & 0x03));
                        else
                                *p++ = 0x00;
                }

                /* data bytes */
                repaper_even_pixels(epd, &p, data, fixed_value, mask, stage);
        } else {
                /*
                 * even scan line, but as lines on display are numbered from 1,
                 * line: 1,3,5,...
                 */
                for (b = 0; b < epd->bytes_per_scan; b++) {
                        if (0 != (line & 0x01) && line / 8 == b)
                                *p++ = 0xc0 >> (line & 0x06);
                        else
                                *p++ = 0x00;
                }

                /* data bytes */
                repaper_all_pixels(epd, &p, data, fixed_value, mask, stage);

                /*
                 * odd scan line, but as lines on display are numbered from 1,
                 * line: 0,2,4,6,...
                 */
                for (b = epd->bytes_per_scan; b > 0; b--) {
                        if (0 == (line & 0x01) && line / 8 == b - 1)
                                *p++ = 0x03 << (line & 0x06);
                        else
                                *p++ = 0x00;
                }
        }

        switch (epd->border_byte) {
        case REPAPER_BORDER_BYTE_NONE:
                break;

        case REPAPER_BORDER_BYTE_ZERO:
                *p++ = 0x00;
                break;

        case REPAPER_BORDER_BYTE_SET:
                switch (stage) {
                case REPAPER_COMPENSATE:
                case REPAPER_WHITE:
                case REPAPER_INVERSE:
                        *p++ = 0x00;
                        break;
                case REPAPER_NORMAL:
                        *p++ = 0xaa;
                        break;
                }
                break;
        }

        repaper_write_buf(epd->spi, 0x0a, epd->line_buffer,
                          p - epd->line_buffer);

        /* Output data to panel */
        repaper_write_val(epd->spi, 0x02, 0x07);

        repaper_spi_mosi_low(epd->spi);
}

static void repaper_frame_fixed(struct repaper_epd *epd, u8 fixed_value,
                                enum repaper_stage stage)
{
        unsigned int line;

        for (line = 0; line < epd->height; line++)
                repaper_one_line(epd, line, NULL, fixed_value, NULL, stage);
}

static void repaper_frame_data(struct repaper_epd *epd, const u8 *image,
                               const u8 *mask, enum repaper_stage stage)
{
        unsigned int line;

        if (!mask) {
                for (line = 0; line < epd->height; line++) {
                        repaper_one_line(epd, line,
                                         &image[line * (epd->width / 8)],
                                         0, NULL, stage);
                }
        } else {
                for (line = 0; line < epd->height; line++) {
                        size_t n = line * epd->width / 8;

                        repaper_one_line(epd, line, &image[n], 0, &mask[n],
                                         stage);
                }
        }
}

static void repaper_frame_fixed_repeat(struct repaper_epd *epd, u8 fixed_value,
                                       enum repaper_stage stage)
{
        u64 start = local_clock();
        u64 end = start + (epd->factored_stage_time * 1000 * 1000);

        do {
                repaper_frame_fixed(epd, fixed_value, stage);
        } while (local_clock() < end);
}

static void repaper_frame_data_repeat(struct repaper_epd *epd, const u8 *image,
                                      const u8 *mask, enum repaper_stage stage)
{
        u64 start = local_clock();
        u64 end = start + (epd->factored_stage_time * 1000 * 1000);

        do {
                repaper_frame_data(epd, image, mask, stage);
        } while (local_clock() < end);
}

static void repaper_get_temperature(struct repaper_epd *epd)
{
        int ret, temperature = 0;
        unsigned int factor10x;

        if (!epd->thermal)
                return;

        ret = thermal_zone_get_temp(epd->thermal, &temperature);
        if (ret) {
                DRM_DEV_ERROR(&epd->spi->dev, "Failed to get temperature (%d)\n", ret);
                return;
        }

        temperature /= 1000;

        if (temperature <= -10)
                factor10x = 170;
        else if (temperature <= -5)
                factor10x = 120;
        else if (temperature <= 5)
                factor10x = 80;
        else if (temperature <= 10)
                factor10x = 40;
        else if (temperature <= 15)
                factor10x = 30;
        else if (temperature <= 20)
                factor10x = 20;
        else if (temperature <= 40)
                factor10x = 10;
        else
                factor10x = 7;

        epd->factored_stage_time = epd->stage_time * factor10x / 10;
}

static void repaper_gray8_to_mono_reversed(u8 *buf, u32 width, u32 height)
{
        u8 *gray8 = buf, *mono = buf;
        int y, xb, i;

        for (y = 0; y < height; y++)
                for (xb = 0; xb < width / 8; xb++) {
                        u8 byte = 0x00;

                        for (i = 0; i < 8; i++) {
                                int x = xb * 8 + i;

                                byte >>= 1;
                                if (gray8[y * width + x] >> 7)
                                        byte |= BIT(7);
                        }
                        *mono++ = byte;
                }
}

static int repaper_fb_dirty(struct drm_framebuffer *fb)
{
        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 repaper_epd *epd = drm_to_epd(fb->dev);
        struct drm_rect clip;
        int idx, ret = 0;
        u8 *buf = NULL;

        if (!drm_dev_enter(fb->dev, &idx))
                return -ENODEV;

        /* repaper can't do partial updates */
        clip.x1 = 0;
        clip.x2 = fb->width;
        clip.y1 = 0;
        clip.y2 = fb->height;

        repaper_get_temperature(epd);

        DRM_DEBUG("Flushing [FB:%d] st=%ums\n", fb->base.id,
                  epd->factored_stage_time);

        buf = kmalloc_array(fb->width, fb->height, GFP_KERNEL);
        if (!buf) {
                ret = -ENOMEM;
                goto out_exit;
        }

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

        drm_fb_xrgb8888_to_gray8(buf, cma_obj->vaddr, fb, &clip);

        if (import_attach) {
                ret = dma_buf_end_cpu_access(import_attach->dmabuf,
                                             DMA_FROM_DEVICE);
                if (ret)
                        goto out_free;
        }

        repaper_gray8_to_mono_reversed(buf, fb->width, fb->height);

        if (epd->partial) {
                repaper_frame_data_repeat(epd, buf, epd->current_frame,
                                          REPAPER_NORMAL);
        } else if (epd->cleared) {
                repaper_frame_data_repeat(epd, epd->current_frame, NULL,
                                          REPAPER_COMPENSATE);
                repaper_frame_data_repeat(epd, epd->current_frame, NULL,
                                          REPAPER_WHITE);
                repaper_frame_data_repeat(epd, buf, NULL, REPAPER_INVERSE);
                repaper_frame_data_repeat(epd, buf, NULL, REPAPER_NORMAL);

                epd->partial = true;
        } else {
                /* Clear display (anything -> white) */
                repaper_frame_fixed_repeat(epd, 0xff, REPAPER_COMPENSATE);
                repaper_frame_fixed_repeat(epd, 0xff, REPAPER_WHITE);
                repaper_frame_fixed_repeat(epd, 0xaa, REPAPER_INVERSE);
                repaper_frame_fixed_repeat(epd, 0xaa, REPAPER_NORMAL);

                /* Assuming a clear (white) screen output an image */
                repaper_frame_fixed_repeat(epd, 0xaa, REPAPER_COMPENSATE);
                repaper_frame_fixed_repeat(epd, 0xaa, REPAPER_WHITE);
                repaper_frame_data_repeat(epd, buf, NULL, REPAPER_INVERSE);
                repaper_frame_data_repeat(epd, buf, NULL, REPAPER_NORMAL);

                epd->cleared = true;
                epd->partial = true;
        }

        memcpy(epd->current_frame, buf, fb->width * fb->height / 8);

        /*
         * An extra frame write is needed if pixels are set in the bottom line,
         * or else grey lines rises up from the pixels
         */
        if (epd->pre_border_byte) {
                unsigned int x;

                for (x = 0; x < (fb->width / 8); x++)
                        if (buf[x + (fb->width * (fb->height - 1) / 8)]) {
                                repaper_frame_data_repeat(epd, buf,
                                                          epd->current_frame,
                                                          REPAPER_NORMAL);
                                break;
                        }
        }

out_free:
        kfree(buf);
out_exit:
        drm_dev_exit(idx);

        return ret;
}

static void power_off(struct repaper_epd *epd)
{
        /* Turn off power and all signals */
        gpiod_set_value_cansleep(epd->reset, 0);
        gpiod_set_value_cansleep(epd->panel_on, 0);
        if (epd->border)
                gpiod_set_value_cansleep(epd->border, 0);

        /* Ensure SPI MOSI and CLOCK are Low before CS Low */
        repaper_spi_mosi_low(epd->spi);

        /* Discharge pulse */
        gpiod_set_value_cansleep(epd->discharge, 1);
        msleep(150);
        gpiod_set_value_cansleep(epd->discharge, 0);
}

static void repaper_pipe_enable(struct drm_simple_display_pipe *pipe,
                                struct drm_crtc_state *crtc_state,
                                struct drm_plane_state *plane_state)
{
        struct repaper_epd *epd = drm_to_epd(pipe->crtc.dev);
        struct spi_device *spi = epd->spi;
        struct device *dev = &spi->dev;
        bool dc_ok = false;
        int i, ret, idx;

        if (!drm_dev_enter(pipe->crtc.dev, &idx))
                return;

        DRM_DEBUG_DRIVER("\n");

        /* Power up sequence */
        gpiod_set_value_cansleep(epd->reset, 0);
        gpiod_set_value_cansleep(epd->panel_on, 0);
        gpiod_set_value_cansleep(epd->discharge, 0);
        if (epd->border)
                gpiod_set_value_cansleep(epd->border, 0);
        repaper_spi_mosi_low(spi);
        usleep_range(5000, 10000);

        gpiod_set_value_cansleep(epd->panel_on, 1);
        /*
         * This delay comes from the repaper.org userspace driver, it's not
         * mentioned in the datasheet.
         */
        usleep_range(10000, 15000);
        gpiod_set_value_cansleep(epd->reset, 1);
        if (epd->border)
                gpiod_set_value_cansleep(epd->border, 1);
        usleep_range(5000, 10000);
        gpiod_set_value_cansleep(epd->reset, 0);
        usleep_range(5000, 10000);
        gpiod_set_value_cansleep(epd->reset, 1);
        usleep_range(5000, 10000);

        /* Wait for COG to become ready */
        for (i = 100; i > 0; i--) {
                if (!gpiod_get_value_cansleep(epd->busy))
                        break;

                usleep_range(10, 100);
        }

        if (!i) {
                DRM_DEV_ERROR(dev, "timeout waiting for panel to become ready.\n");
                power_off(epd);
                goto out_exit;
        }

        repaper_read_id(spi);
        ret = repaper_read_id(spi);
        if (ret != REPAPER_RID_G2_COG_ID) {
                if (ret < 0)
                        dev_err(dev, "failed to read chip (%d)\n", ret);
                else
                        dev_err(dev, "wrong COG ID 0x%02x\n", ret);
                power_off(epd);
                goto out_exit;
        }

        /* Disable OE */
        repaper_write_val(spi, 0x02, 0x40);

        ret = repaper_read_val(spi, 0x0f);
        if (ret < 0 || !(ret & 0x80)) {
                if (ret < 0)
                        DRM_DEV_ERROR(dev, "failed to read chip (%d)\n", ret);
                else
                        DRM_DEV_ERROR(dev, "panel is reported broken\n");
                power_off(epd);
                goto out_exit;
        }

        /* Power saving mode */
        repaper_write_val(spi, 0x0b, 0x02);
        /* Channel select */
        repaper_write_buf(spi, 0x01, epd->channel_select, 8);
        /* High power mode osc */
        repaper_write_val(spi, 0x07, 0xd1);
        /* Power setting */
        repaper_write_val(spi, 0x08, 0x02);
        /* Vcom level */
        repaper_write_val(spi, 0x09, 0xc2);
        /* Power setting */
        repaper_write_val(spi, 0x04, 0x03);
        /* Driver latch on */
        repaper_write_val(spi, 0x03, 0x01);
        /* Driver latch off */
        repaper_write_val(spi, 0x03, 0x00);
        usleep_range(5000, 10000);

        /* Start chargepump */
        for (i = 0; i < 4; ++i) {
                /* Charge pump positive voltage on - VGH/VDL on */
                repaper_write_val(spi, 0x05, 0x01);
                msleep(240);

                /* Charge pump negative voltage on - VGL/VDL on */
                repaper_write_val(spi, 0x05, 0x03);
                msleep(40);

                /* Charge pump Vcom on - Vcom driver on */
                repaper_write_val(spi, 0x05, 0x0f);
                msleep(40);

                /* check DC/DC */
                ret = repaper_read_val(spi, 0x0f);
                if (ret < 0) {
                        DRM_DEV_ERROR(dev, "failed to read chip (%d)\n", ret);
                        power_off(epd);
                        goto out_exit;
                }

                if (ret & 0x40) {
                        dc_ok = true;
                        break;
                }
        }

        if (!dc_ok) {
                DRM_DEV_ERROR(dev, "dc/dc failed\n");
                power_off(epd);
                goto out_exit;
        }

        /*
         * Output enable to disable
         * The userspace driver sets this to 0x04, but the datasheet says 0x06
         */
        repaper_write_val(spi, 0x02, 0x04);

        epd->partial = false;
out_exit:
        drm_dev_exit(idx);
}

static void repaper_pipe_disable(struct drm_simple_display_pipe *pipe)
{
        struct repaper_epd *epd = drm_to_epd(pipe->crtc.dev);
        struct spi_device *spi = epd->spi;
        unsigned int line;

        /*
         * This callback is not protected by drm_dev_enter/exit since we want to
         * turn off the display on regular driver unload. It's highly unlikely
         * that the underlying SPI controller is gone should this be called after
         * unplug.
         */

        DRM_DEBUG_DRIVER("\n");

        /* Nothing frame */
        for (line = 0; line < epd->height; line++)
                repaper_one_line(epd, 0x7fffu, NULL, 0x00, NULL,
                                 REPAPER_COMPENSATE);

        /* 2.7" */
        if (epd->border) {
                /* Dummy line */
                repaper_one_line(epd, 0x7fffu, NULL, 0x00, NULL,
                                 REPAPER_COMPENSATE);
                msleep(25);
                gpiod_set_value_cansleep(epd->border, 0);
                msleep(200);
                gpiod_set_value_cansleep(epd->border, 1);
        } else {
                /* Border dummy line */
                repaper_one_line(epd, 0x7fffu, NULL, 0x00, NULL,
                                 REPAPER_NORMAL);
                msleep(200);
        }

        /* not described in datasheet */
        repaper_write_val(spi, 0x0b, 0x00);
        /* Latch reset turn on */
        repaper_write_val(spi, 0x03, 0x01);
        /* Power off charge pump Vcom */
        repaper_write_val(spi, 0x05, 0x03);
        /* Power off charge pump neg voltage */
        repaper_write_val(spi, 0x05, 0x01);
        msleep(120);
        /* Discharge internal */
        repaper_write_val(spi, 0x04, 0x80);
        /* turn off all charge pumps */
        repaper_write_val(spi, 0x05, 0x00);
        /* Turn off osc */
        repaper_write_val(spi, 0x07, 0x01);
        msleep(50);

        power_off(epd);
}

static void repaper_pipe_update(struct drm_simple_display_pipe *pipe,
                                struct drm_plane_state *old_state)
{
        struct drm_plane_state *state = pipe->plane.state;
        struct drm_rect rect;

        if (!pipe->crtc.state->active)
                return;

        if (drm_atomic_helper_damage_merged(old_state, state, &rect))
                repaper_fb_dirty(state->fb);
}

static const struct drm_simple_display_pipe_funcs repaper_pipe_funcs = {
        .enable = repaper_pipe_enable,
        .disable = repaper_pipe_disable,
        .update = repaper_pipe_update,
        .prepare_fb = drm_gem_fb_simple_display_pipe_prepare_fb,
};

static int repaper_connector_get_modes(struct drm_connector *connector)
{
        struct repaper_epd *epd = drm_to_epd(connector->dev);
        struct drm_display_mode *mode;

        mode = drm_mode_duplicate(connector->dev, epd->mode);
        if (!mode) {
                DRM_ERROR("Failed to duplicate mode\n");
                return 0;
        }

        drm_mode_set_name(mode);
        mode->type |= DRM_MODE_TYPE_PREFERRED;
        drm_mode_probed_add(connector, mode);

        connector->display_info.width_mm = mode->width_mm;
        connector->display_info.height_mm = mode->height_mm;

        return 1;
}

static const struct drm_connector_helper_funcs repaper_connector_hfuncs = {
        .get_modes = repaper_connector_get_modes,
};

static const struct drm_connector_funcs repaper_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 repaper_mode_config_funcs = {
        .fb_create = drm_gem_fb_create_with_dirty,
        .atomic_check = drm_atomic_helper_check,
        .atomic_commit = drm_atomic_helper_commit,
};

static const uint32_t repaper_formats[] = {
        DRM_FORMAT_XRGB8888,
};

static const struct drm_display_mode repaper_e1144cs021_mode = {
        DRM_SIMPLE_MODE(128, 96, 29, 22),
};

static const u8 repaper_e1144cs021_cs[] = { 0x00, 0x00, 0x00, 0x00,
                                            0x00, 0x0f, 0xff, 0x00 };

static const struct drm_display_mode repaper_e1190cs021_mode = {
        DRM_SIMPLE_MODE(144, 128, 36, 32),
};

static const u8 repaper_e1190cs021_cs[] = { 0x00, 0x00, 0x00, 0x03,
                                            0xfc, 0x00, 0x00, 0xff };

static const struct drm_display_mode repaper_e2200cs021_mode = {
        DRM_SIMPLE_MODE(200, 96, 46, 22),
};

static const u8 repaper_e2200cs021_cs[] = { 0x00, 0x00, 0x00, 0x00,
                                            0x01, 0xff, 0xe0, 0x00 };

static const struct drm_display_mode repaper_e2271cs021_mode = {
        DRM_SIMPLE_MODE(264, 176, 57, 38),
};

static const u8 repaper_e2271cs021_cs[] = { 0x00, 0x00, 0x00, 0x7f,
                                            0xff, 0xfe, 0x00, 0x00 };

DEFINE_DRM_GEM_CMA_FOPS(repaper_fops);

static const struct drm_driver repaper_driver = {
        .driver_features        = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
        .fops                   = &repaper_fops,
        DRM_GEM_CMA_DRIVER_OPS_VMAP,
        .name                   = "repaper",
        .desc                   = "Pervasive Displays RePaper e-ink panels",
        .date                   = "20170405",
        .major                  = 1,
        .minor                  = 0,
};

static const struct of_device_id repaper_of_match[] = {
        { .compatible = "pervasive,e1144cs021", .data = (void *)E1144CS021 },
        { .compatible = "pervasive,e1190cs021", .data = (void *)E1190CS021 },
        { .compatible = "pervasive,e2200cs021", .data = (void *)E2200CS021 },
        { .compatible = "pervasive,e2271cs021", .data = (void *)E2271CS021 },
        {},
};
MODULE_DEVICE_TABLE(of, repaper_of_match);

static const struct spi_device_id repaper_id[] = {
        { "e1144cs021", E1144CS021 },
        { "e1190cs021", E1190CS021 },
        { "e2200cs021", E2200CS021 },
        { "e2271cs021", E2271CS021 },
        { },
};
MODULE_DEVICE_TABLE(spi, repaper_id);

static int repaper_probe(struct spi_device *spi)
{
        const struct drm_display_mode *mode;
        const struct spi_device_id *spi_id;
        struct device *dev = &spi->dev;
        enum repaper_model model;
        const char *thermal_zone;
        struct repaper_epd *epd;
        size_t line_buffer_size;
        struct drm_device *drm;
        const void *match;
        int ret;

        match = device_get_match_data(dev);
        if (match) {
                model = (enum repaper_model)match;
        } else {
                spi_id = spi_get_device_id(spi);
                model = (enum repaper_model)spi_id->driver_data;
        }

        /* The SPI device is used to allocate dma memory */
        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;
                }
        }

        epd = devm_drm_dev_alloc(dev, &repaper_driver,
                                 struct repaper_epd, drm);
        if (IS_ERR(epd))

                return PTR_ERR(epd);

        drm = &epd->drm;

        ret = drmm_mode_config_init(drm);
        if (ret)
                return ret;
        drm->mode_config.funcs = &repaper_mode_config_funcs;

        epd->spi = spi;

        epd->panel_on = devm_gpiod_get(dev, "panel-on", GPIOD_OUT_LOW);
        if (IS_ERR(epd->panel_on)) {
                ret = PTR_ERR(epd->panel_on);
                if (ret != -EPROBE_DEFER)
                        DRM_DEV_ERROR(dev, "Failed to get gpio 'panel-on'\n");
                return ret;
        }

        epd->discharge = devm_gpiod_get(dev, "discharge", GPIOD_OUT_LOW);
        if (IS_ERR(epd->discharge)) {
                ret = PTR_ERR(epd->discharge);
                if (ret != -EPROBE_DEFER)
                        DRM_DEV_ERROR(dev, "Failed to get gpio 'discharge'\n");
                return ret;
        }

        epd->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
        if (IS_ERR(epd->reset)) {
                ret = PTR_ERR(epd->reset);
                if (ret != -EPROBE_DEFER)
                        DRM_DEV_ERROR(dev, "Failed to get gpio 'reset'\n");
                return ret;
        }

        epd->busy = devm_gpiod_get(dev, "busy", GPIOD_IN);
        if (IS_ERR(epd->busy)) {
                ret = PTR_ERR(epd->busy);
                if (ret != -EPROBE_DEFER)
                        DRM_DEV_ERROR(dev, "Failed to get gpio 'busy'\n");
                return ret;
        }

        if (!device_property_read_string(dev, "pervasive,thermal-zone",
                                         &thermal_zone)) {
                epd->thermal = thermal_zone_get_zone_by_name(thermal_zone);
                if (IS_ERR(epd->thermal)) {
                        DRM_DEV_ERROR(dev, "Failed to get thermal zone: %s\n", thermal_zone);
                        return PTR_ERR(epd->thermal);
                }
        }

        switch (model) {
        case E1144CS021:
                mode = &repaper_e1144cs021_mode;
                epd->channel_select = repaper_e1144cs021_cs;
                epd->stage_time = 480;
                epd->bytes_per_scan = 96 / 4;
                epd->middle_scan = true; /* data-scan-data */
                epd->pre_border_byte = false;
                epd->border_byte = REPAPER_BORDER_BYTE_ZERO;
                break;

        case E1190CS021:
                mode = &repaper_e1190cs021_mode;
                epd->channel_select = repaper_e1190cs021_cs;
                epd->stage_time = 480;
                epd->bytes_per_scan = 128 / 4 / 2;
                epd->middle_scan = false; /* scan-data-scan */
                epd->pre_border_byte = false;
                epd->border_byte = REPAPER_BORDER_BYTE_SET;
                break;

        case E2200CS021:
                mode = &repaper_e2200cs021_mode;
                epd->channel_select = repaper_e2200cs021_cs;
                epd->stage_time = 480;
                epd->bytes_per_scan = 96 / 4;
                epd->middle_scan = true; /* data-scan-data */
                epd->pre_border_byte = true;
                epd->border_byte = REPAPER_BORDER_BYTE_NONE;
                break;

        case E2271CS021:
                epd->border = devm_gpiod_get(dev, "border", GPIOD_OUT_LOW);
                if (IS_ERR(epd->border)) {
                        ret = PTR_ERR(epd->border);
                        if (ret != -EPROBE_DEFER)
                                DRM_DEV_ERROR(dev, "Failed to get gpio 'border'\n");
                        return ret;
                }

                mode = &repaper_e2271cs021_mode;
                epd->channel_select = repaper_e2271cs021_cs;
                epd->stage_time = 630;
                epd->bytes_per_scan = 176 / 4;
                epd->middle_scan = true; /* data-scan-data */
                epd->pre_border_byte = true;
                epd->border_byte = REPAPER_BORDER_BYTE_NONE;
                break;

        default:
                return -ENODEV;
        }

        epd->mode = mode;
        epd->width = mode->hdisplay;
        epd->height = mode->vdisplay;
        epd->factored_stage_time = epd->stage_time;

        line_buffer_size = 2 * epd->width / 8 + epd->bytes_per_scan + 2;
        epd->line_buffer = devm_kzalloc(dev, line_buffer_size, GFP_KERNEL);
        if (!epd->line_buffer)
                return -ENOMEM;

        epd->current_frame = devm_kzalloc(dev, epd->width * epd->height / 8,
                                          GFP_KERNEL);
        if (!epd->current_frame)
                return -ENOMEM;

        drm->mode_config.min_width = mode->hdisplay;
        drm->mode_config.max_width = mode->hdisplay;
        drm->mode_config.min_height = mode->vdisplay;
        drm->mode_config.max_height = mode->vdisplay;

        drm_connector_helper_add(&epd->connector, &repaper_connector_hfuncs);
        ret = drm_connector_init(drm, &epd->connector, &repaper_connector_funcs,
                                 DRM_MODE_CONNECTOR_SPI);
        if (ret)
                return ret;

        ret = drm_simple_display_pipe_init(drm, &epd->pipe, &repaper_pipe_funcs,
                                           repaper_formats, ARRAY_SIZE(repaper_formats),
                                           NULL, &epd->connector);
        if (ret)
                return ret;

        drm_mode_config_reset(drm);

        ret = drm_dev_register(drm, 0);
        if (ret)
                return ret;

        spi_set_drvdata(spi, drm);

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

        drm_fbdev_generic_setup(drm, 0);

        return 0;
}

static int repaper_remove(struct spi_device *spi)
{
        struct drm_device *drm = spi_get_drvdata(spi);

        drm_dev_unplug(drm);
        drm_atomic_helper_shutdown(drm);

        return 0;
}

static void repaper_shutdown(struct spi_device *spi)
{
        drm_atomic_helper_shutdown(spi_get_drvdata(spi));
}

static struct spi_driver repaper_spi_driver = {
        .driver = {
                .name = "repaper",
                .of_match_table = repaper_of_match,
        },
        .id_table = repaper_id,
        .probe = repaper_probe,
        .remove = repaper_remove,
        .shutdown = repaper_shutdown,
};
module_spi_driver(repaper_spi_driver);

MODULE_DESCRIPTION("Pervasive Displays RePaper DRM driver");
MODULE_AUTHOR("Noralf Trønnes");
MODULE_LICENSE("GPL");