[PATCH 1/2 v3] drm/panel: Augment the TPO TPG110 bindings

[PATCH 1/2 v3] drm/panel: Augment the TPO TPG110 bindings

[Linus Walleij]

The TPO TPG110 bindings were using the DPI bindings (popular
in the fbdev subsystem) but this misses the finer points
learned in the DRM subsystem.

We need to augment the bindings for proper DRM integration:
the timings are expressed by the hardware, not put into the
device tree. I.e. this hardware is self-describing and can
report the resolutions and timings needed. It should not
be described in the device tree.

Further the device was incorrectly modeled with GPIO lines
instead of an SPI child, even though the device was using
SPI.

No known deployments of the device using device tree
exist, so it should be fine to augment the bindings.

Cc: devicetree@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Rewrite to reflect the fact that the display should be
  an SPI child device using 3WIRE SPI.
ChangeLog v1->v2:
- Expand some sections to make it clear what kind of device
  this is and that the serial protocol it uses is not
  I2C.
---
 .../bindings/display/panel/tpo,tpg110.txt     | 83 ++++++++++++-------
 1 file changed, 54 insertions(+), 29 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/panel/tpo,tpg110.txt b/Documentation/devicetree/bindings/display/panel/tpo,tpg110.txt
index f5e3c6f2095a..4b90a0929a46 100644
--- a/Documentation/devicetree/bindings/display/panel/tpo,tpg110.txt
+++ b/Documentation/devicetree/bindings/display/panel/tpo,tpg110.txt
@@ -1,47 +1,72 @@
 TPO TPG110 Panel
 ================
 
-This binding builds on the DPI bindings, adding a few properties
-as a superset of a DPI. See panel-dpi.txt for the required DPI
-bindings.
+This panel driver is a component that acts as an intermediary
+between an RGB output and a variety of panels. The panel
+driver is strapped up in electronics to the desired resolution
+and other properties, and has a control interface over 3WIRE
+SPI. By talking to the TPG110 over SPI, the strapped properties
+can be discovered and the hardware is therefore mostly
+self-describing.
+
+       +--------+
+SPI -> |  TPO   | -> physical display
+RGB -> | TPG110 |
+       +--------+
+
+If some electrical strap or alternate resolution is desired,
+this can be set up by taking software control of the display
+over the SPI interface. The interface can also adjust
+for properties of the display such as gamma correction and
+certain electrical driving levels.
+
+The TPG110 does not know the physical dimensions of the panel
+connected, so this needs to be specified in the device tree.
+
+It requires a GPIO line for control of its reset line.
+
+The serial protocol has line names that resemble I2C but the
+protocol is not I2C but 3WIRE SPI.
 
 Required properties:
-- compatible : "tpo,tpg110"
+- compatible : one of:
+  "ste,nomadik-nhk15-display", "tpo,tpg110"
+  "tpo,tpg110"
 - grestb-gpios : panel reset GPIO
-- scen-gpios : serial control enable GPIO
-- scl-gpios : serial control clock line GPIO
-- sda-gpios : serial control data line GPIO
+- width-mm : see display/panel/panel-common.txt
+- height-mm : see display/panel/panel-common.txt
+
+The device needs to be a child of an SPI bus, see
+spi/spi-bus.txt. The SPI child must set the following
+properties:
+- spi-3wire
+- spi-3wire-high-impedance-turnaround
+- spi-max-frequency = <3000000>;
+as these are characteristics of this device.
 
-Required nodes:
-- Video port for DPI input, see panel-dpi.txt
-- Panel timing for DPI setup, see panel-dpi.txt
+The device node can contain one 'port' child node with one child
+'endpoint' node, according to the bindings defined in
+media/video-interfaces.txt. This node should describe panel's video bus.
 
 Example
 -------
 
-panel {
-	compatible = "tpo,tpg110", "panel-dpi";
-	grestb-gpios = <&stmpe_gpio44 5 GPIO_ACTIVE_LOW>;
-	scen-gpios = <&gpio0 6 GPIO_ACTIVE_LOW>;
-	scl-gpios = <&gpio0 5 GPIO_ACTIVE_HIGH>;
-	sda-gpios = <&gpio0 4 GPIO_ACTIVE_HIGH>;
+panel: display@0 {
+	compatible = "tpo,tpg110";
+	reg = <0>;
+	spi-3wire;
+	spi-3wire-high-impedance-turnaround;
+	/* 320 ns min period ~= 3 MHz */
+	spi-max-frequency = <3000000>;
+	/* Width and height from data sheet */
+	width-mm = <116>;
+	height-mm = <87>;
+	grestb-gpios = <&foo_gpio 5 GPIO_ACTIVE_LOW>;
 	backlight = <&bl>;
 
 	port {
 		nomadik_clcd_panel: endpoint {
-			remote-endpoint = <&nomadik_clcd_pads>;
+			remote-endpoint = <&foo>;
 		};
 	};
-
-	panel-timing {
-		clock-frequency = <33200000>;
-		hactive = <800>;
-		hback-porch = <216>;
-		hfront-porch = <40>;
-		hsync-len = <1>;
-		vactive = <480>;
-		vback-porch = <35>;
-		vfront-porch = <10>;
-		vsync-len = <1>;
-	};
 };
-- 
2.17.1

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[PATCH 2/2 v3] drm/panel: Add a driver for the TPO TPG110

[Linus Walleij]

The TPO (Toppoly) TPG110 is a pretty generic display driver
similar in vein to the Ilitek 93xx devices. It is not a panel
per se but a driver used with several low-cost noname panels.

This is used on the Nomadik NHK15 combined with a OSD
OSD057VA01CT display for WVGA 800x480.

The driver is pretty minimalistic right now but can be
extended to handle non-default polarities, gamma correction
etc.

The driver is based on the baked-in code in
drivers/video/fbdev/amba-clcd-nomadik.c which will be
decomissioned once this us upstream.

The device tree bindings already exist in:
Documentation/devicetree/bindings/display/panel/tpo,tpg110.txt

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Rewrite as an SPI child device.
---
 MAINTAINERS                              |   7 +
 drivers/gpu/drm/panel/Kconfig            |  10 +
 drivers/gpu/drm/panel/Makefile           |   1 +
 drivers/gpu/drm/panel/panel-tpo-tpg110.c | 505 +++++++++++++++++++++++
 4 files changed, 523 insertions(+)
 create mode 100644 drivers/gpu/drm/panel/panel-tpo-tpg110.c

diff --git a/MAINTAINERS b/MAINTAINERS
index a5b256b25905..b3f95dc8f681 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4718,6 +4718,13 @@ DRM DRIVER FOR TDFX VIDEO CARDS
 S:	Orphan / Obsolete
 F:	drivers/gpu/drm/tdfx/
 
+DRM DRIVER FOR TPO TPG110 PANELS
+M:	Linus Walleij <linus.walleij@linaro.org>
+T:	git git://anongit.freedesktop.org/drm/drm-misc
+S:	Maintained
+F:	drivers/gpu/drm/panel/panel-tpo-tpg110.c
+F:	Documentation/devicetree/bindings/display/panel/tpo,tpg110.txt
+
 DRM DRIVER FOR USB DISPLAYLINK VIDEO ADAPTERS
 M:	Dave Airlie <airlied@redhat.com>
 S:	Odd Fixes
diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index 6020c30a33b3..b2c8b02894b1 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -186,4 +186,14 @@ config DRM_PANEL_SITRONIX_ST7789V
 	  Say Y here if you want to enable support for the Sitronix
 	  ST7789V controller for 240x320 LCD panels
 
+config DRM_PANEL_TPO_TPG110
+	tristate "TPO TPG 800x400 panel"
+	depends on OF && SPI && GPIOLIB
+	depends on BACKLIGHT_CLASS_DEVICE
+	select VIDEOMODE_HELPERS
+	help
+	  Say Y here if you want to enable support for TPO TPG110
+	  400CH LTPS TFT LCD Single Chip Digital Driver for up to
+	  800x400 LCD panels.
+
 endmenu
diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
index 5ccaaa9d13af..9b3a0629d255 100644
--- a/drivers/gpu/drm/panel/Makefile
+++ b/drivers/gpu/drm/panel/Makefile
@@ -19,3 +19,4 @@ obj-$(CONFIG_DRM_PANEL_SEIKO_43WVF1G) += panel-seiko-43wvf1g.o
 obj-$(CONFIG_DRM_PANEL_SHARP_LQ101R1SX01) += panel-sharp-lq101r1sx01.o
 obj-$(CONFIG_DRM_PANEL_SHARP_LS043T1LE01) += panel-sharp-ls043t1le01.o
 obj-$(CONFIG_DRM_PANEL_SITRONIX_ST7789V) += panel-sitronix-st7789v.o
+obj-$(CONFIG_DRM_PANEL_TPO_TPG110) += panel-tpo-tpg110.o
diff --git a/drivers/gpu/drm/panel/panel-tpo-tpg110.c b/drivers/gpu/drm/panel/panel-tpo-tpg110.c
new file mode 100644
index 000000000000..db3d52db61ca
--- /dev/null
+++ b/drivers/gpu/drm/panel/panel-tpo-tpg110.c
@@ -0,0 +1,505 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Panel driver for the TPO TPG110 400CH LTPS TFT LCD Single Chip
+ * Digital Driver.
+ *
+ * This chip drives a TFT LCD, so it does not know what kind of
+ * display is actually connected to it, so the width and height of that
+ * display needs to be supplied from the machine configuration.
+ *
+ * Author:
+ * Linus Walleij <linus.wallei@linaro.org>
+ */
+#include <drm/drmP.h>
+#include <drm/drm_panel.h>
+
+#include <linux/backlight.h>
+#include <linux/bitops.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/spi/spi.h>
+
+#include <video/of_videomode.h>
+#include <video/videomode.h>
+
+#define TPG110_TEST			0x00
+#define TPG110_CHIPID			0x01
+#define TPG110_CTRL1			0x02
+#define TPG110_RES_MASK			GENMASK(2, 0)
+#define TPG110_RES_800X480		0x07
+#define TPG110_RES_640X480		0x06
+#define TPG110_RES_480X272		0x05
+#define TPG110_RES_480X640		0x04
+#define TPG110_RES_480X272_D		0x01 /* Dual scan: outputs 800x480 */
+#define TPG110_RES_400X240_D		0x00 /* Dual scan: outputs 800x480 */
+#define TPG110_CTRL2			0x03
+#define TPG110_CTRL2_PM			BIT(0)
+#define TPG110_CTRL2_RES_PM_CTRL	BIT(7)
+
+/**
+ * struct tpg110_panel_mode - lookup struct for the supported modes
+ */
+struct tpg110_panel_mode {
+	/**
+	 * @name: the name of this panel
+	 */
+	const char *name;
+	/**
+	 * @magic: the magic value from the detection register
+	 */
+	u32 magic;
+	/**
+	 * @mode: the DRM display mode for this panel
+	 */
+	struct drm_display_mode mode;
+	/**
+	 * @bus_flags: the DRM bus flags for this panel e.g. inverted clock
+	 */
+	u32 bus_flags;
+};
+
+/**
+ * struct tpg110 - state container for the TPG110 panel
+ */
+struct tpg110 {
+	/**
+	 * @dev: the container device
+	 */
+	struct device *dev;
+	/**
+	 * @spi: the corresponding SPI device
+	 */
+	struct spi_device *spi;
+	/**
+	 * @panel: the DRM panel instance for this device
+	 */
+	struct drm_panel panel;
+	/**
+	 * @backlight: backlight for this panel
+	 */
+	struct backlight_device *backlight;
+	/**
+	 * @panel_type: the panel mode as detected
+	 */
+	const struct tpg110_panel_mode *panel_mode;
+	/**
+	 * @width: the width of this panel in mm
+	 */
+	u32 width;
+	/**
+	 * @height: the height of this panel in mm
+	 */
+	u32 height;
+	/**
+	 * @grestb: reset GPIO line
+	 */
+	struct gpio_desc *grestb;
+};
+
+/*
+ * TPG110 modes, these are the simple modes, the dualscan modes that
+ * take 400x240 or 480x272 in and display as 800x480 are not listed.
+ */
+static const struct tpg110_panel_mode tpg110_modes[] = {
+	{
+		.name = "800x480 RGB",
+		.magic = TPG110_RES_800X480,
+		.mode = {
+			.clock = 33200,
+			.hdisplay = 800,
+			.hsync_start = 800 + 40,
+			.hsync_end = 800 + 40 + 1,
+			.htotal = 800 + 40 + 1 + 216,
+			.vdisplay = 480,
+			.vsync_start = 480 + 10,
+			.vsync_end = 480 + 10 + 1,
+			.vtotal = 480 + 10 + 1 + 35,
+			.vrefresh = 60,
+		},
+	},
+	{
+		.name = "640x480 RGB",
+		.magic = TPG110_RES_640X480,
+		.mode = {
+			.clock = 25200,
+			.hdisplay = 640,
+			.hsync_start = 640 + 24,
+			.hsync_end = 640 + 24 + 1,
+			.htotal = 640 + 24 + 1 + 136,
+			.vdisplay = 480,
+			.vsync_start = 480 + 18,
+			.vsync_end = 480 + 18 + 1,
+			.vtotal = 480 + 18 + 1 + 27,
+			.vrefresh = 60,
+		},
+	},
+	{
+		.name = "480x272 RGB",
+		.magic = TPG110_RES_480X272,
+		.mode = {
+			.clock = 9000,
+			.hdisplay = 480,
+			.hsync_start = 480 + 2,
+			.hsync_end = 480 + 2 + 1,
+			.htotal = 480 + 2 + 1 + 43,
+			.vdisplay = 272,
+			.vsync_start = 272 + 2,
+			.vsync_end = 272 + 2 + 1,
+			.vtotal = 272 + 2 + 1 + 12,
+			.vrefresh = 60,
+		},
+	},
+	{
+		.name = "480x640 RGB",
+		.magic = TPG110_RES_480X640,
+		.mode = {
+			.clock = 20500,
+			.hdisplay = 480,
+			.hsync_start = 480 + 2,
+			.hsync_end = 480 + 2 + 1,
+			.htotal = 480 + 2 + 1 + 43,
+			.vdisplay = 640,
+			.vsync_start = 640 + 4,
+			.vsync_end = 640 + 4 + 1,
+			.vtotal = 640 + 4 + 1 + 8,
+			.vrefresh = 60,
+		},
+	},
+	{
+		.name = "400x240 RGB",
+		.magic = TPG110_RES_400X240_D,
+		.mode = {
+			.clock = 8300,
+			.hdisplay = 400,
+			.hsync_start = 400 + 20,
+			.hsync_end = 400 + 20 + 1,
+			.htotal = 400 + 20 + 1 + 108,
+			.vdisplay = 240,
+			.vsync_start = 240 + 2,
+			.vsync_end = 240 + 2 + 1,
+			.vtotal = 240 + 2 + 1 + 20,
+			.vrefresh = 60,
+		},
+	},
+};
+
+static inline struct tpg110 *
+to_tpg110(struct drm_panel *panel)
+{
+	return container_of(panel, struct tpg110, panel);
+}
+
+static u8 tpg110_readwrite_reg(struct tpg110 *tpg, bool write,
+			       u8 address, u8 outval)
+{
+	struct spi_message m;
+	struct spi_transfer t[2];
+	u8 buf[2];
+	int ret;
+
+	spi_message_init(&m);
+	memset(t, 0, sizeof(t));
+
+	if (write) {
+		/*
+		 * Clear address bit 0, 1 when writing, just to be sure
+		 * The actual bit indicating a write here is bit 1, bit
+		 * 0 is just surplus to pad it up to 8 bits.
+		 */
+		buf[0] = address << 2;
+		buf[0] &= ~0x03;
+		buf[1] = outval;
+
+		t[0].bits_per_word = 8;
+		t[0].tx_buf = &buf[0];
+		t[0].len = 1;
+
+		t[1].tx_buf = &buf[1];
+		t[1].len = 1;
+		t[1].bits_per_word = 8;
+	} else {
+		/* Set address bit 0 to 1 to read */
+		buf[0] = address << 1;
+		buf[0] |= 0x01;
+
+		/*
+		 * The last bit/clock is Hi-Z turnaround cycle, so we need
+		 * to send only 7 bits here. The 8th bit is the high impedance
+		 * turn-around cycle.
+		 */
+		t[0].bits_per_word = 7;
+		t[0].tx_buf = &buf[0];
+		t[0].len = 1;
+
+		t[1].rx_buf = &buf[1];
+		t[1].len = 1;
+		t[1].bits_per_word = 8;
+	}
+
+	spi_message_add_tail(&t[0], &m);
+	spi_message_add_tail(&t[1], &m);
+	ret = spi_sync(tpg->spi, &m);
+	if (ret) {
+		dev_err(tpg->dev, "SPI message error %d\n", ret);
+		return ret;
+	}
+	if (write)
+		return 0;
+	/* Read */
+	return buf[1];
+}
+
+static u8 tpg110_read_reg(struct tpg110 *tpg, u8 address)
+{
+	return tpg110_readwrite_reg(tpg, false, address, 0);
+}
+
+static void tpg110_write_reg(struct tpg110 *tpg, u8 address, u8 outval)
+{
+	tpg110_readwrite_reg(tpg, true, address, outval);
+}
+
+static int tpg110_startup(struct tpg110 *tpg)
+{
+	u8 val;
+	int i;
+
+	/* De-assert the reset signal */
+	gpiod_set_value_cansleep(tpg->grestb, 0);
+	mdelay(1);
+	dev_info(tpg->dev, "de-asserted GRESTB\n");
+
+	/* Test display communication */
+	tpg110_write_reg(tpg, TPG110_TEST, 0x55);
+	val = tpg110_read_reg(tpg, TPG110_TEST);
+	if (val != 0x55) {
+		dev_err(tpg->dev, "failed communication test\n");
+		return -ENODEV;
+	}
+
+	val = tpg110_read_reg(tpg, TPG110_CHIPID);
+	dev_info(tpg->dev, "TPG110 chip ID: %d version: %d\n",
+		 val >> 4, val & 0x0f);
+
+	/* Show display resolution */
+	val = tpg110_read_reg(tpg, TPG110_CTRL1);
+	val &= TPG110_RES_MASK;
+	switch (val) {
+	case TPG110_RES_400X240_D:
+		dev_info(tpg->dev,
+			 "IN 400x240 RGB -> OUT 800x480 RGB (dual scan)");
+		break;
+	case TPG110_RES_480X272_D:
+		dev_info(tpg->dev,
+			 "IN 480x272 RGB -> OUT 800x480 RGB (dual scan)");
+		break;
+	case TPG110_RES_480X640:
+		dev_info(tpg->dev, "480x640 RGB");
+		break;
+	case TPG110_RES_480X272:
+		dev_info(tpg->dev, "480x272 RGB");
+		break;
+	case TPG110_RES_640X480:
+		dev_info(tpg->dev, "640x480 RGB");
+		break;
+	case TPG110_RES_800X480:
+		dev_info(tpg->dev, "800x480 RGB");
+		break;
+	default:
+		dev_info(tpg->dev, "ILLEGAL RESOLUTION");
+		break;
+	}
+
+	/* From the producer side, this is the same resolution */
+	if (val == TPG110_RES_480X272_D)
+		val = TPG110_RES_480X272;
+
+	for (i = 0; i < ARRAY_SIZE(tpg110_modes); i++) {
+		const struct tpg110_panel_mode *pm;
+
+		pm = &tpg110_modes[i];
+		if (pm->magic == val) {
+			tpg->panel_mode = pm;
+			break;
+		}
+	}
+	if (i == ARRAY_SIZE(tpg110_modes)) {
+		dev_err(tpg->dev, "unsupported mode (%02x) detected\n",
+			val);
+		return -ENODEV;
+	}
+
+	val = tpg110_read_reg(tpg, TPG110_CTRL2);
+	dev_info(tpg->dev, "resolution and standby is controlled by %s\n",
+		 (val & TPG110_CTRL2_RES_PM_CTRL) ? "software" : "hardware");
+	/* Take control over resolution and standby */
+	val |= TPG110_CTRL2_RES_PM_CTRL;
+	tpg110_write_reg(tpg, TPG110_CTRL2, val);
+
+	return 0;
+}
+
+static int tpg110_disable(struct drm_panel *panel)
+{
+	struct tpg110 *tpg = to_tpg110(panel);
+	u8 val;
+
+	/* Put chip into standby */
+	val = tpg110_read_reg(tpg, TPG110_CTRL2_PM);
+	val &= ~TPG110_CTRL2_PM;
+	tpg110_write_reg(tpg, TPG110_CTRL2_PM, val);
+
+	if (tpg->backlight) {
+		tpg->backlight->props.power = FB_BLANK_POWERDOWN;
+		tpg->backlight->props.state |= BL_CORE_FBBLANK;
+		backlight_update_status(tpg->backlight);
+	}
+
+	return 0;
+}
+
+static int tpg110_enable(struct drm_panel *panel)
+{
+	struct tpg110 *tpg = to_tpg110(panel);
+	u8 val;
+
+	if (tpg->backlight) {
+		tpg->backlight->props.state &= ~BL_CORE_FBBLANK;
+		tpg->backlight->props.power = FB_BLANK_UNBLANK;
+		backlight_update_status(tpg->backlight);
+	}
+
+	/* Take chip out of standby */
+	val = tpg110_read_reg(tpg, TPG110_CTRL2_PM);
+	val |= TPG110_CTRL2_PM;
+	tpg110_write_reg(tpg, TPG110_CTRL2_PM, val);
+
+	return 0;
+}
+
+/**
+ * tpg110_get_modes() - return the appropriate mode
+ * @panel: the panel to get the mode for
+ *
+ * This currently does not present a forest of modes, instead it
+ * presents the mode that is configured for the system under use,
+ * and which is detected by reading the registers of the display.
+ */
+static int tpg110_get_modes(struct drm_panel *panel)
+{
+	struct drm_connector *connector = panel->connector;
+	struct tpg110 *tpg = to_tpg110(panel);
+	struct drm_display_mode *mode;
+
+	strncpy(connector->display_info.name, tpg->panel_mode->name,
+		DRM_DISPLAY_INFO_LEN);
+	connector->display_info.width_mm = tpg->width;
+	connector->display_info.height_mm = tpg->height;
+	connector->display_info.bus_flags = tpg->panel_mode->bus_flags;
+
+	mode = drm_mode_duplicate(panel->drm, &tpg->panel_mode->mode);
+	drm_mode_set_name(mode);
+	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
+
+	mode->width_mm = tpg->width;
+	mode->height_mm = tpg->height;
+
+	drm_mode_probed_add(connector, mode);
+
+	return 1;
+}
+
+static const struct drm_panel_funcs tpg110_drm_funcs = {
+	.disable = tpg110_disable,
+	.enable = tpg110_enable,
+	.get_modes = tpg110_get_modes,
+};
+
+static int tpg110_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *backlight;
+	struct tpg110 *tpg;
+	int ret;
+
+	tpg = devm_kzalloc(dev, sizeof(*tpg), GFP_KERNEL);
+	if (!tpg)
+		return -ENOMEM;
+	tpg->dev = dev;
+
+	/* We get the physical display dimensions from the DT */
+	ret = of_property_read_u32(np, "width-mm", &tpg->width);
+	if (ret)
+		dev_err(dev, "no panel width specified\n");
+	ret = of_property_read_u32(np, "height-mm", &tpg->height);
+	if (ret)
+		dev_err(dev, "no panel height specified\n");
+
+	/* Look for some optional backlight */
+	backlight = of_parse_phandle(np, "backlight", 0);
+	if (backlight) {
+		tpg->backlight = of_find_backlight_by_node(backlight);
+		of_node_put(backlight);
+
+		if (!tpg->backlight)
+			return -EPROBE_DEFER;
+	}
+
+	/* This asserts the GRESTB signal, putting the display into reset */
+	tpg->grestb = devm_gpiod_get(dev, "grestb", GPIOD_OUT_HIGH);
+	if (IS_ERR(tpg->grestb)) {
+		dev_err(dev, "no GRESTB GPIO\n");
+		return -ENODEV;
+	}
+
+	spi->bits_per_word = 8;
+	ret = spi_setup(spi);
+	if (ret < 0) {
+		dev_err(dev, "spi setup failed.\n");
+		return ret;
+	}
+	tpg->spi = spi;
+
+	ret = tpg110_startup(tpg);
+	if (ret)
+		return ret;
+
+	drm_panel_init(&tpg->panel);
+	tpg->panel.dev = dev;
+	tpg->panel.funcs = &tpg110_drm_funcs;
+	spi_set_drvdata(spi, tpg);
+
+	return drm_panel_add(&tpg->panel);
+}
+
+static int tpg110_remove(struct spi_device *spi)
+{
+	struct tpg110 *tpg = spi_get_drvdata(spi);
+
+	drm_panel_remove(&tpg->panel);
+	return 0;
+}
+
+static const struct of_device_id tpg110_match[] = {
+	{ .compatible = "tpo,tpg110", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, tpg110_match);
+
+static struct spi_driver tpg110_driver = {
+	.probe		= tpg110_probe,
+	.remove		= tpg110_remove,
+	.driver		= {
+		.name	= "tpo-tpg110-panel",
+		.of_match_table = tpg110_match,
+	},
+};
+module_spi_driver(tpg110_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("TPO TPG110 panel driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1

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Re: [PATCH 1/2 v3] drm/panel: Augment the TPO TPG110 bindings

[Rob Herring]

On Tue, 25 Sep 2018 16:35:58 +0200, Linus Walleij wrote:
> The TPO TPG110 bindings were using the DPI bindings (popular
> in the fbdev subsystem) but this misses the finer points
> learned in the DRM subsystem.
> 
> We need to augment the bindings for proper DRM integration:
> the timings are expressed by the hardware, not put into the
> device tree. I.e. this hardware is self-describing and can
> report the resolutions and timings needed. It should not
> be described in the device tree.
> 
> Further the device was incorrectly modeled with GPIO lines
> instead of an SPI child, even though the device was using
> SPI.
> 
> No known deployments of the device using device tree
> exist, so it should be fine to augment the bindings.
> 
> Cc: devicetree@vger.kernel.org
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Rewrite to reflect the fact that the display should be
>   an SPI child device using 3WIRE SPI.
> ChangeLog v1->v2:
> - Expand some sections to make it clear what kind of device
>   this is and that the serial protocol it uses is not
>   I2C.
> ---
>  .../bindings/display/panel/tpo,tpg110.txt     | 83 ++++++++++++-------
>  1 file changed, 54 insertions(+), 29 deletions(-)
> 

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