[PATCH 0/4] drm/tinydrm: Add support for Pervasive Displays RePaper monochrome e-ink panels

[PATCH 0/4] drm/tinydrm: Add support for Pervasive Displays RePaper monochrome e-ink panels

[Noralf Trønnes]

This adds support for the 1.44", 1.9", 2.0" and 2.7" Pervasive Diplays
monochrome e-ink panels. The code was taken from the userspace driver
available through repaper.org.

Monochrome
Since drm doesn't have support for monochrome, I have added a helper to
convert XRGB8888 to greyscale8. XRGB8888 is very common so that's why I
chose that format, but maybe some YUV format is better suited, I don't
know. There are some greyscale e-ink panels, so that's why I chose
greyscale instead of going directly to monochrome.

I have hacked together a python drm library to make it easy to use these
displays, mainly targeted at the maker community:
https://github.com/notro/pydrm

Noralf.

Noralf Trønnes (4):
  of: Add vendor prefix for Pervasive Displays
  dt-bindings: Add Pervasive Displays RePaper bindings
  drm/tinydrm: Add tinydrm_xrgb8888_to_gray8() helper
  drm/tinydrm: Add RePaper e-ink driver

 .../devicetree/bindings/display/repaper.txt        |   52 +
 .../devicetree/bindings/vendor-prefixes.txt        |    1 +
 MAINTAINERS                                        |    6 +
 drivers/gpu/drm/tinydrm/Kconfig                    |   12 +
 drivers/gpu/drm/tinydrm/Makefile                   |    1 +
 drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c     |   74 +-
 drivers/gpu/drm/tinydrm/repaper.c                  | 1095 ++++++++++++++++++++
 include/drm/tinydrm/tinydrm-helpers.h              |    1 +
 8 files changed, 1240 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/display/repaper.txt
 create mode 100644 drivers/gpu/drm/tinydrm/repaper.c

-- 
2.7.4

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[PATCH 1/4] of: Add vendor prefix for Pervasive Displays

[Noralf Trønnes]

Pervasive Displays Inc. designs, develops, and manufactures low-power
electrophoretic (e-ink) display modules and supporting electronics for
commercial and industrial display applications.

Signed-off-by: Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
---
 Documentation/devicetree/bindings/vendor-prefixes.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/vendor-prefixes.txt b/Documentation/devicetree/bindings/vendor-prefixes.txt
index c03d201..6885c75 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.txt
+++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
@@ -240,6 +240,7 @@ oxsemi	Oxford Semiconductor, Ltd.
 panasonic	Panasonic Corporation
 parade	Parade Technologies Inc.
 pericom	Pericom Technology Inc.
+pervasive	Pervasive Displays, Inc.
 phytec	PHYTEC Messtechnik GmbH
 picochip	Picochip Ltd
 pine64	Pine64
-- 
2.7.4

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[PATCH 2/4] dt-bindings: Add Pervasive Displays RePaper bindings

[Noralf Trønnes]

Add device-tree binding documentation for the 1.44", 1.9", 2.0" and 2.7"
display panels.

Signed-off-by: Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
---
 .../devicetree/bindings/display/repaper.txt        | 52 ++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/repaper.txt

diff --git a/Documentation/devicetree/bindings/display/repaper.txt b/Documentation/devicetree/bindings/display/repaper.txt
new file mode 100644
index 0000000..f5f9f9c
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/repaper.txt
@@ -0,0 +1,52 @@
+Pervasive Displays RePaper branded e-ink displays
+
+Required properties:
+- compatible:		"pervasive,e1144cs021" for 1.44" display
+			"pervasive,e1190cs021" for 1.9" display
+			"pervasive,e2200cs021" for 2.0" display
+			"pervasive,e2271cs021" for 2.7" display
+
+- panel-on-gpios:	Timing controller power control
+- discharge-gpios:	Discharge control
+- reset-gpios:		RESET pin
+- busy-gpios:		BUSY pin
+
+Required property for e2271cs021:
+- border-gpios:		Border control
+
+The node for this driver must be a child node of a SPI controller, hence
+all mandatory properties described in ../spi/spi-bus.txt must be specified.
+
+Optional property:
+- pervasive,thermal-zone:	name of thermometer's thermal zone
+
+Example:
+
+	display_temp: lm75@48 {
+		compatible = "lm75b";
+		reg = <0x48>;
+		#thermal-sensor-cells = <0>;
+	};
+
+	thermal-zones {
+		display {
+			polling-delay-passive = <0>;
+			polling-delay = <0>;
+			thermal-sensors = <&display_temp>;
+		};
+	};
+
+	papirus27@0{
+		compatible = "pervasive,e2271cs021";
+		reg = <0>;
+
+		spi-max-frequency = <8000000>;
+
+		panel-on-gpios = <&gpio 23 0>;
+		border-gpios = <&gpio 14 0>;
+		discharge-gpios = <&gpio 15 0>;
+		reset-gpios = <&gpio 24 0>;
+		busy-gpios = <&gpio 25 0>;
+
+		pervasive,thermal-zone = "display";
+	};
-- 
2.7.4

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[PATCH 3/4] drm/tinydrm: Add tinydrm_xrgb8888_to_gray8() helper

[Noralf Trønnes]

Drm has no monochrome or greyscale support so add a conversion
from the common format XR24.

Also reorder includes into the common order.

Signed-off-by: Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
---
 drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 74 +++++++++++++++++++++++++-
 include/drm/tinydrm/tinydrm-helpers.h          |  1 +
 2 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
index d4cda33..75808bb 100644
--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
@@ -7,13 +7,15 @@
  * (at your option) any later version.
  */
 
-#include <drm/tinydrm/tinydrm.h>
-#include <drm/tinydrm/tinydrm-helpers.h>
 #include <linux/backlight.h>
+#include <linux/dma-buf.h>
 #include <linux/pm.h>
 #include <linux/spi/spi.h>
 #include <linux/swab.h>
 
+#include <drm/tinydrm/tinydrm.h>
+#include <drm/tinydrm/tinydrm-helpers.h>
+
 static unsigned int spi_max;
 module_param(spi_max, uint, 0400);
 MODULE_PARM_DESC(spi_max, "Set a lower SPI max transfer size");
@@ -181,6 +183,74 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
 EXPORT_SYMBOL(tinydrm_xrgb8888_to_rgb565);
 
 /**
+ * tinydrm_xrgb8888_to_gray8 - Convert XRGB8888 to grayscale
+ * @dst: 8-bit grayscale destination buffer
+ * @fb: DRM framebuffer
+ *
+ * Drm doesn't have native monochrome or grayscale support.
+ * Such drivers can announce the commonly supported XR24 format to userspace
+ * and use this function to convert to the native format.
+ *
+ * Monochrome drivers will use the most significant bit,
+ * where 1 means foreground color and 0 background color.
+ *
+ * ITU BT.601 is used for the RGB -> luma (brightness) conversion.
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int tinydrm_xrgb8888_to_gray8(u8 *dst, 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;
+	unsigned int x, y, pitch = fb->pitches[0];
+	int ret = 0;
+	void *buf;
+	u32 *src;
+
+	if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
+		return -EINVAL;
+	/*
+	 * The cma memory is write-combined so reads are uncached.
+	 * Speed up by fetching one line at a time.
+	 */
+	buf = kmalloc(pitch, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	if (import_attach) {
+		ret = dma_buf_begin_cpu_access(import_attach->dmabuf,
+					       DMA_FROM_DEVICE);
+		if (ret)
+			goto err_free;
+	}
+
+	for (y = 0; y < fb->height; y++) {
+		src = cma_obj->vaddr + (y * pitch);
+		memcpy(buf, src, pitch);
+		src = buf;
+		for (x = 0; x < fb->width; x++) {
+			u8 r = (*src & 0x00ff0000) >> 16;
+			u8 g = (*src & 0x0000ff00) >> 8;
+			u8 b =  *src & 0x000000ff;
+
+			/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
+			*dst++ = (3 * r + 6 * g + b) / 10;
+			src++;
+		}
+	}
+
+	if (import_attach)
+		ret = dma_buf_end_cpu_access(import_attach->dmabuf,
+					     DMA_FROM_DEVICE);
+err_free:
+	kfree(buf);
+
+	return ret;
+}
+EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
+
+/**
  * tinydrm_of_find_backlight - Find backlight device in device-tree
  * @dev: Device
  *
diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
index 9b9b6cf..a6c387f 100644
--- a/include/drm/tinydrm/tinydrm-helpers.h
+++ b/include/drm/tinydrm/tinydrm-helpers.h
@@ -43,6 +43,7 @@ void tinydrm_swab16(u16 *dst, void *vaddr, struct drm_framebuffer *fb,
 void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
 				struct drm_framebuffer *fb,
 				struct drm_clip_rect *clip, bool swap);
+int tinydrm_xrgb8888_to_gray8(u8 *dst, struct drm_framebuffer *fb);
 
 struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
 int tinydrm_enable_backlight(struct backlight_device *backlight);
-- 
2.7.4

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[PATCH 4/4] drm/tinydrm: Add RePaper e-ink driver

[Noralf Trønnes]

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.

Signed-off-by: Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
---
 MAINTAINERS                       |    6 +
 drivers/gpu/drm/tinydrm/Kconfig   |   12 +
 drivers/gpu/drm/tinydrm/Makefile  |    1 +
 drivers/gpu/drm/tinydrm/repaper.c | 1095 +++++++++++++++++++++++++++++++++++++
 4 files changed, 1114 insertions(+)
 create mode 100644 drivers/gpu/drm/tinydrm/repaper.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 757d487..800afa2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4446,6 +4446,12 @@ M:	Dave Airlie <airlied-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
 S:	Odd Fixes
 F:	drivers/gpu/drm/mgag200/
 
+DRM DRIVER FOR PERVASIVE DISPLAYS REPAPER PANELS
+M:	Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.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/
diff --git a/drivers/gpu/drm/tinydrm/Kconfig b/drivers/gpu/drm/tinydrm/Kconfig
index 3504c53..9596e44 100644
--- a/drivers/gpu/drm/tinydrm/Kconfig
+++ b/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.
diff --git a/drivers/gpu/drm/tinydrm/Makefile b/drivers/gpu/drm/tinydrm/Makefile
index 7a3604c..95bb4d4 100644
--- a/drivers/gpu/drm/tinydrm/Makefile
+++ b/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
diff --git a/drivers/gpu/drm/tinydrm/repaper.c b/drivers/gpu/drm/tinydrm/repaper.c
new file mode 100644
index 0000000..d1eaa88
--- /dev/null
+++ b/drivers/gpu/drm/tinydrm/repaper.c
@@ -0,0 +1,1095 @@
+/*
+ * 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) {
+				u16 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");
-- 
2.7.4

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Re: [PATCH 4/4] drm/tinydrm: Add RePaper e-ink driver

[Emil Velikov]

Hi Noralf,

Small drive-by comment, noticed while going through my morning coffee.
By no means a full review.

On 2 June 2017 at 12:49, Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org> wrote:


> +/* 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) {
> +                               u16 pixel_mask = repaper_interleave_bits(mask[b - 1]);
> +
> +                               pixel_mask = (pixel_mask ^ pixels) & 0x5555;
> +                               pixel_mask |= pixel_mask << 1;

The second u16 pixel_mask seems very suspicious - likely a copy/paste mistake ?

-Emil
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Re: [PATCH 4/4] drm/tinydrm: Add RePaper e-ink driver

[Noralf Trønnes]

Hi Emil,


Den 07.06.2017 11.30, skrev Emil Velikov:
> Hi Noralf,
>
> Small drive-by comment, noticed while going through my morning coffee.
> By no means a full review.
>
> On 2 June 2017 at 12:49, Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org> wrote:
>
>
>> +/* 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) {
>> +                               u16 pixel_mask = repaper_interleave_bits(mask[b - 1]);
>> +
>> +                               pixel_mask = (pixel_mask ^ pixels) & 0x5555;
>> +                               pixel_mask |= pixel_mask << 1;
> The second u16 pixel_mask seems very suspicious - likely a copy/paste mistake ?

Actually it's a correct copy. The same pattern is used in three places.
I did look at the datasheet to try and understand what was going on,
but the current and previous frame is applied in normal and inverted
form in several stages, the pixels are converted to black/white/nochange
and then I lost track of it all.
So I decided that the Pervasive people who wrote the driver probably
knew what they where doing. At least it works!

Noralf.

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Re: [PATCH 4/4] drm/tinydrm: Add RePaper e-ink driver

[Ilia Mirkin]

On Wed, Jun 7, 2017 at 7:52 AM, Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org> wrote:
> Hi Emil,
>
>
> Den 07.06.2017 11.30, skrev Emil Velikov:
>>
>> Hi Noralf,
>>
>> Small drive-by comment, noticed while going through my morning coffee.
>> By no means a full review.
>>
>> On 2 June 2017 at 12:49, Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org> wrote:
>>
>>
>>> +/* 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) {
>>> +                               u16 pixel_mask =
>>> repaper_interleave_bits(mask[b - 1]);
>>> +
>>> +                               pixel_mask = (pixel_mask ^ pixels) &
>>> 0x5555;
>>> +                               pixel_mask |= pixel_mask << 1;
>>
>> The second u16 pixel_mask seems very suspicious - likely a copy/paste
>> mistake ?
>
>
> Actually it's a correct copy. The same pattern is used in three places.
> I did look at the datasheet to try and understand what was going on,
> but the current and previous frame is applied in normal and inverted
> form in several stages, the pixels are converted to black/white/nochange
> and then I lost track of it all.
> So I decided that the Pervasive people who wrote the driver probably
> knew what they where doing. At least it works!

It's doubling up the bits... 0x5555 is a 0101010101010101 pattern, so
pixel_mask |= pixel_mask << 1 (after pixel_mask is x & 0x5555) is just
saying that the same bit should be repeated twice.

As for why you'd want to do that ... no clue. Maybe it's a
2-bit-per-pixel packed mask and you want to set each pixel to 11 or 00
here?
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Re: [PATCH 4/4] drm/tinydrm: Add RePaper e-ink driver

[Emil Velikov]

On 7 June 2017 at 12:52, Noralf Trønnes <noralf@tronnes.org> wrote:
> Hi Emil,
>
>
> Den 07.06.2017 11.30, skrev Emil Velikov:
>>
>> Hi Noralf,
>>
>> Small drive-by comment, noticed while going through my morning coffee.
>> By no means a full review.
>>
>> On 2 June 2017 at 12:49, Noralf Trønnes <noralf@tronnes.org> wrote:
>>
>>
>>> +/* 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) {
>>> +                               u16 pixel_mask =
>>> repaper_interleave_bits(mask[b - 1]);
>>> +
>>> +                               pixel_mask = (pixel_mask ^ pixels) &
>>> 0x5555;
>>> +                               pixel_mask |= pixel_mask << 1;
>>
>> The second u16 pixel_mask seems very suspicious - likely a copy/paste
>> mistake ?
>
>
> Actually it's a correct copy. The same pattern is used in three places.
> I did look at the datasheet to try and understand what was going on,
> but the current and previous frame is applied in normal and inverted
> form in several stages, the pixels are converted to black/white/nochange
> and then I lost track of it all.
> So I decided that the Pervasive people who wrote the driver probably
> knew what they where doing. At least it works!
>
What I meant was:

Within the 'if (mask)' block you have a second, shadowing declaration
of pixel_mask.
Hence all the calculation done within is discarded and not used
further down in the code.

Am I missing something?

-Emil
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Re: [PATCH 4/4] drm/tinydrm: Add RePaper e-ink driver

[Noralf Trønnes]

Den 07.06.2017 14.11, skrev Ilia Mirkin:
> On Wed, Jun 7, 2017 at 7:52 AM, Noralf Trønnes <noralf@tronnes.org> wrote:
>> Hi Emil,
>>
>>
>> Den 07.06.2017 11.30, skrev Emil Velikov:
>>> Hi Noralf,
>>>
>>> Small drive-by comment, noticed while going through my morning coffee.
>>> By no means a full review.
>>>
>>> On 2 June 2017 at 12:49, Noralf Trønnes <noralf@tronnes.org> wrote:
>>>
>>>
>>>> +/* 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) {
>>>> +                               u16 pixel_mask =
>>>> repaper_interleave_bits(mask[b - 1]);
>>>> +
>>>> +                               pixel_mask = (pixel_mask ^ pixels) &
>>>> 0x5555;
>>>> +                               pixel_mask |= pixel_mask << 1;
>>> The second u16 pixel_mask seems very suspicious - likely a copy/paste
>>> mistake ?
>>
>> Actually it's a correct copy. The same pattern is used in three places.
>> I did look at the datasheet to try and understand what was going on,
>> but the current and previous frame is applied in normal and inverted
>> form in several stages, the pixels are converted to black/white/nochange
>> and then I lost track of it all.
>> So I decided that the Pervasive people who wrote the driver probably
>> knew what they where doing. At least it works!
> It's doubling up the bits... 0x5555 is a 0101010101010101 pattern, so
> pixel_mask |= pixel_mask << 1 (after pixel_mask is x & 0x5555) is just
> saying that the same bit should be repeated twice.
>
> As for why you'd want to do that ... no clue. Maybe it's a
> 2-bit-per-pixel packed mask and you want to set each pixel to 11 or 00
> here?
>

Yes each pixel is represented with 2 bits:
11 - black
10 - white
00 - nothing

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Re: [PATCH 4/4] drm/tinydrm: Add RePaper e-ink driver

[Noralf Trønnes]

Den 07.06.2017 14.14, skrev Emil Velikov:
> On 7 June 2017 at 12:52, Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org> wrote:
>> Hi Emil,
>>
>>
>> Den 07.06.2017 11.30, skrev Emil Velikov:
>>> Hi Noralf,
>>>
>>> Small drive-by comment, noticed while going through my morning coffee.
>>> By no means a full review.
>>>
>>> On 2 June 2017 at 12:49, Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org> wrote:
>>>
>>>
>>>> +/* 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) {
>>>> +                               u16 pixel_mask =
>>>> repaper_interleave_bits(mask[b - 1]);
>>>> +
>>>> +                               pixel_mask = (pixel_mask ^ pixels) &
>>>> 0x5555;
>>>> +                               pixel_mask |= pixel_mask << 1;
>>> The second u16 pixel_mask seems very suspicious - likely a copy/paste
>>> mistake ?
>>
>> Actually it's a correct copy. The same pattern is used in three places.
>> I did look at the datasheet to try and understand what was going on,
>> but the current and previous frame is applied in normal and inverted
>> form in several stages, the pixels are converted to black/white/nochange
>> and then I lost track of it all.
>> So I decided that the Pervasive people who wrote the driver probably
>> knew what they where doing. At least it works!
>>
> What I meant was:
>
> Within the 'if (mask)' block you have a second, shadowing declaration
> of pixel_mask.
> Hence all the calculation done within is discarded and not used
> further down in the code.

Ah, I see, it's indeed lost and useless.
I'll see what happens if I don't shadow the variable.
Thanks.

Noralf.

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Re: [PATCH 1/4] of: Add vendor prefix for Pervasive Displays

[Rob Herring]

On Fri, Jun 02, 2017 at 01:49:12PM +0200, Noralf Trønnes wrote:
> Pervasive Displays Inc. designs, develops, and manufactures low-power
> electrophoretic (e-ink) display modules and supporting electronics for
> commercial and industrial display applications.
> 
> Signed-off-by: Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
> ---
>  Documentation/devicetree/bindings/vendor-prefixes.txt | 1 +
>  1 file changed, 1 insertion(+)

Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
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Re: [PATCH 2/4] dt-bindings: Add Pervasive Displays RePaper bindings

[Rob Herring]

On Fri, Jun 02, 2017 at 01:49:13PM +0200, Noralf Trønnes wrote:
> Add device-tree binding documentation for the 1.44", 1.9", 2.0" and 2.7"
> display panels.
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> ---
>  .../devicetree/bindings/display/repaper.txt        | 52 ++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/repaper.txt

Acked-by: Rob Herring <robh@kernel.org>
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