drm/tinydrm: Add RePaper e-ink driver

This adds support for the Pervasive Displays RePaper branded displays.
The controller code is taken from the userspace driver available
through repaper.org. Only the V231 film is supported since the others
are EOL.
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1496934875-51984-5-git-send-email-noralf@tronnes.org

MAINTAINERS

@@ -4453,6 +4453,12 @@ M:	Dave Airlie <airlied@redhat.com>
 S:	Odd Fixes
 F:	drivers/gpu/drm/mgag200/
 
+DRM DRIVER FOR PERVASIVE DISPLAYS REPAPER PANELS
+M:	Noralf Trønnes <noralf@tronnes.org>
+S:	Maintained
+F:	drivers/gpu/drm/tinydrm/repaper.c
+F:	Documentation/devicetree/bindings/display/repaper.txt
+
 DRM DRIVER FOR RAGE 128 VIDEO CARDS
 S:	Orphan / Obsolete
 F:	drivers/gpu/drm/r128/

drivers/gpu/drm/tinydrm/Kconfig

@@ -19,3 +19,15 @@ config TINYDRM_MI0283QT
 	help
 	  DRM driver for the Multi-Inno MI0283QT display panel
 	  If M is selected the module will be called mi0283qt.
+
+config TINYDRM_REPAPER
+	tristate "DRM support for Pervasive Displays RePaper panels (V231)"
+	depends on DRM_TINYDRM && SPI
+	help
+	  DRM driver for the following Pervasive Displays panels:
+	  1.44" TFT EPD Panel (E1144CS021)
+	  1.90" TFT EPD Panel (E1190CS021)
+	  2.00" TFT EPD Panel (E2200CS021)
+	  2.71" TFT EPD Panel (E2271CS021)
+
+	  If M is selected the module will be called repaper.

drivers/gpu/drm/tinydrm/Makefile

@@ -5,3 +5,4 @@ obj-$(CONFIG_TINYDRM_MIPI_DBI)		+= mipi-dbi.o
 
 # Displays
 obj-$(CONFIG_TINYDRM_MI0283QT)		+= mi0283qt.o
+obj-$(CONFIG_TINYDRM_REPAPER)		+= repaper.o

drivers/gpu/drm/tinydrm/repaper.c

+/*
+ * 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
+ *
+ * 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 <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/sched/clock.h>
+#include <linux/spi/spi.h>
+#include <linux/thermal.h>
+
+#include <drm/tinydrm/tinydrm.h>
+#include <drm/tinydrm/tinydrm-helpers.h>
+
+#define REPAPER_RID_G2_COG_ID	0x12
+
+enum repaper_model {
+	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 tinydrm_device tinydrm;
+	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 enabled;
+	bool cleared;
+	bool partial;
+};
+
+static inline struct repaper_epd *
+epd_from_tinydrm(struct tinydrm_device *tdev)
+{
+	return container_of(tdev, struct repaper_epd, tinydrm);
+}
+
+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 = kmalloc(len, GFP_KERNEL);
+		if (!txbuf) {
+			ret = -ENOMEM;
+			goto out_free;
+		}
+		memcpy(txbuf, tx, len);
+	}
+
+	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) {
+		dev_err(&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_file *file_priv,
+			    unsigned int flags, unsigned int color,
+			    struct drm_clip_rect *clips,
+			    unsigned int num_clips)
+{
+	struct tinydrm_device *tdev = fb->dev->dev_private;
+	struct repaper_epd *epd = epd_from_tinydrm(tdev);
+	u8 *buf = NULL;
+	int ret = 0;
+
+	mutex_lock(&tdev->dirty_lock);
+
+	if (!epd->enabled)
+		goto out_unlock;
+
+	/* fbdev can flush even when we're not interested */
+	if (tdev->pipe.plane.fb != fb)
+		goto out_unlock;
+
+	repaper_get_temperature(epd);
+
+	DRM_DEBUG("Flushing [FB:%d] st=%ums\n", fb->base.id,
+		  epd->factored_stage_time);
+
+	buf = kmalloc(fb->width * fb->height, GFP_KERNEL);
+	if (!buf) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	ret = tinydrm_xrgb8888_to_gray8(buf, fb);
+	if (ret)
+		goto out_unlock;
+
+	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_unlock:
+	mutex_unlock(&tdev->dirty_lock);
+
+	if (ret)
+		dev_err(fb->dev->dev, "Failed to update display (%d)\n", ret);
+	kfree(buf);
+
+	return ret;
+}
+
+static const struct drm_framebuffer_funcs repaper_fb_funcs = {
+	.destroy	= drm_fb_cma_destroy,
+	.create_handle	= drm_fb_cma_create_handle,
+	.dirty		= repaper_fb_dirty,
+};
+
+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 tinydrm_device *tdev = pipe_to_tinydrm(pipe);
+	struct repaper_epd *epd = epd_from_tinydrm(tdev);
+	struct spi_device *spi = epd->spi;
+	struct device *dev = &spi->dev;
+	bool dc_ok = false;
+	int i, ret;
+
+	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) {
+		dev_err(dev, "timeout waiting for panel to become ready.\n");
+		power_off(epd);
+		return;
+	}
+
+	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);
+		return;
+	}
+
+	/* Disable OE */
+	repaper_write_val(spi, 0x02, 0x40);
+
+	ret = repaper_read_val(spi, 0x0f);
+	if (ret < 0 || !(ret & 0x80)) {
+		if (ret < 0)
+			dev_err(dev, "failed to read chip (%d)\n", ret);
+		else
+			dev_err(dev, "panel is reported broken\n");
+		power_off(epd);
+		return;
+	}
+
+	/* 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) {
+			dev_err(dev, "failed to read chip (%d)\n", ret);
+			power_off(epd);
+			return;
+		}
+
+		if (ret & 0x40) {
+			dc_ok = true;
+			break;
+		}
+	}
+
+	if (!dc_ok) {
+		dev_err(dev, "dc/dc failed\n");
+		power_off(epd);
+		return;
+	}
+
+	/*
+	 * Output enable to disable
+	 * The userspace driver sets this to 0x04, but the datasheet says 0x06
+	 */
+	repaper_write_val(spi, 0x02, 0x04);
+
+	epd->enabled = true;
+	epd->partial = false;
+}
+
+static void repaper_pipe_disable(struct drm_simple_display_pipe *pipe)
+{
+	struct tinydrm_device *tdev = pipe_to_tinydrm(pipe);
+	struct repaper_epd *epd = epd_from_tinydrm(tdev);
+	struct spi_device *spi = epd->spi;
+	unsigned int line;
+
+	DRM_DEBUG_DRIVER("\n");
+
+	mutex_lock(&tdev->dirty_lock);
+	epd->enabled = false;
+	mutex_unlock(&tdev->dirty_lock);
+
+	/* 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 const struct drm_simple_display_pipe_funcs repaper_pipe_funcs = {
+	.enable = repaper_pipe_enable,
+	.disable = repaper_pipe_disable,
+	.update = tinydrm_display_pipe_update,
+	.prepare_fb = tinydrm_display_pipe_prepare_fb,
+};
+
+static const uint32_t repaper_formats[] = {
+	DRM_FORMAT_XRGB8888,
+};
+
+static const struct drm_display_mode repaper_e1144cs021_mode = {
+	TINYDRM_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 = {
+	TINYDRM_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 = {
+	TINYDRM_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 = {
+	TINYDRM_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 struct drm_driver repaper_driver = {
+	.driver_features	= DRIVER_GEM | DRIVER_MODESET | DRIVER_PRIME |
+				  DRIVER_ATOMIC,
+	.fops			= &repaper_fops,
+	TINYDRM_GEM_DRIVER_OPS,
+	.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;
+	const struct of_device_id *match;
+	struct device *dev = &spi->dev;
+	struct tinydrm_device *tdev;
+	enum repaper_model model;
+	const char *thermal_zone;
+	struct repaper_epd *epd;
+	size_t line_buffer_size;
+	int ret;
+
+	match = of_match_device(repaper_of_match, dev);
+	if (match) {
+		model = (enum repaper_model)match->data;
+	} else {
+		spi_id = spi_get_device_id(spi);
+		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_kzalloc(dev, sizeof(*epd), GFP_KERNEL);
+	if (!epd)
+		return -ENOMEM;
+
+	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)
+			dev_err(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)
+			dev_err(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)
+			dev_err(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)
+			dev_err(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)) {
+			dev_err(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)
+				dev_err(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->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;
+
+	tdev = &epd->tinydrm;
+
+	ret = devm_tinydrm_init(dev, tdev, &repaper_fb_funcs, &repaper_driver);
+	if (ret)
+		return ret;
+
+	ret = tinydrm_display_pipe_init(tdev, &repaper_pipe_funcs,
+					DRM_MODE_CONNECTOR_VIRTUAL,
+					repaper_formats,
+					ARRAY_SIZE(repaper_formats), mode, 0);
+	if (ret)
+		return ret;
+
+	drm_mode_config_reset(tdev->drm);
+
+	ret = devm_tinydrm_register(tdev);
+	if (ret)
+		return ret;
+
+	spi_set_drvdata(spi, tdev);
+
+	DRM_DEBUG_DRIVER("Initialized %s:%s @%uMHz on minor %d\n",
+			 tdev->drm->driver->name, dev_name(dev),
+			 spi->max_speed_hz / 1000000,
+			 tdev->drm->primary->index);
+
+	return 0;
+}
+
+static void repaper_shutdown(struct spi_device *spi)
+{
+	struct tinydrm_device *tdev = spi_get_drvdata(spi);
+
+	tinydrm_shutdown(tdev);
+}
+
+static struct spi_driver repaper_spi_driver = {
+	.driver = {
+		.name = "repaper",
+		.owner = THIS_MODULE,
+		.of_match_table = repaper_of_match,
+	},
+	.id_table = repaper_id,
+	.probe = repaper_probe,
+	.shutdown = repaper_shutdown,
+};
+module_spi_driver(repaper_spi_driver);
+
+MODULE_DESCRIPTION("Pervasive Displays RePaper DRM driver");
+MODULE_AUTHOR("Noralf Trønnes");
+MODULE_LICENSE("GPL");