[RESEND PATCH v5 0/2] Add a Himax HX8837 display controller driver

[RESEND PATCH v5 0/2] Add a Himax HX8837 display controller driver

[Lubomir Rintel]

Hi,

please take a look at the patches chained to this messages and consider
applying them. They add support for the controller that drives the panel
on the OLPC XO laptops.

The only change since the previous version is the Reviewed-by tag in DT
bindings.

Compared to v3 the bindings have been converted to YAML and the driver
itself has been rewritten without any fancy features such as the
self-refresh so that the bare minimum works before the rest can be figured
out. Detailed change logs are in individual patches.

Tested on an OLPC XO-1.75 laptop.

Thank you
Lubo

[RESEND PATCH v5 0/2] Add a Himax HX8837 display controller driver

[Lubomir Rintel]

Hi,

please take a look at the patches chained to this messages and consider
applying them. They add support for the controller that drives the panel
on the OLPC XO laptops.

The only change since the previous version is the Reviewed-by tag in DT
bindings.

Compared to v3 the bindings have been converted to YAML and the driver
itself has been rewritten without any fancy features such as the
self-refresh so that the bare minimum works before the rest can be figured
out. Detailed change logs are in individual patches.

Tested on an OLPC XO-1.75 laptop.

Thank you
Lubo



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[RESEND PATCH v5 1/2] dt-bindings: display: himax,hx8837: Add Himax HX8837 bindings

[Lubomir Rintel]

Himax HX8837 is a secondary display controller used to drive the panel
on OLPC platforms.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Rob Herring <robh@kernel.org>

---
Changes since v4:
- Rob's Reviewed-by

Changes since v3:
- Moved to bindings/display/
- Added the ports
- Converted to YAML
- Removed Pavel's Ack, because the changes are substantial

Changes since v2:
- s/betweend/between/

Changes since v1:
- s/load-gpio/load-gpios/
- Use interrupt bindings instead of gpio for the IRQ

 .../bindings/display/bridge/himax,hx8837.yaml | 96 +++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/himax,hx8837.yaml

diff --git a/Documentation/devicetree/bindings/display/bridge/himax,hx8837.yaml b/Documentation/devicetree/bindings/display/bridge/himax,hx8837.yaml
new file mode 100644
index 0000000000000..f5b0a00f5089d
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/himax,hx8837.yaml
@@ -0,0 +1,96 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2018,2019,2020 Lubomir Rintel <lkundrak@v3.sk>
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/himax,hx8837.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: HX8837 Display Controller Device Tree Bindings
+
+maintainers:
+  - Lubomir Rintel <lkundrak@v3.sk>
+
+properties:
+  compatible:
+    const: himax,hx8837
+
+  reg:
+    const: 0xd
+
+  load-gpios:
+    maxItems: 1
+    description: GPIO specifier of DCON_LOAD pin (active high)
+
+  stat-gpios:
+    minItems: 2
+    description: GPIO specifier of DCON_STAT0 and DCON_STAT1 pins (active high)
+
+  interrupts:
+    maxItems: 1
+    description: Interrupt specifier of DCON_IRQ pin (edge falling)
+
+  ports:
+    type: object
+
+    properties:
+      port@0:
+        type: object
+        description: |
+          Video port for RGB input.
+
+      port@1:
+        type: object
+        description: |
+          Video port connected to the panel.
+
+    required:
+      - port@0
+      - port@1
+
+required:
+  - compatible
+  - reg
+  - load-gpios
+  - stat-gpios
+  - interrupts
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        
+        lcd-controller@d {
+            compatible = "himax,hx8837";
+            reg = <0x0d>;
+            stat-gpios = <&gpio 100 GPIO_ACTIVE_HIGH>,
+                         <&gpio 101 GPIO_ACTIVE_HIGH>;
+            load-gpios = <&gpio 142 GPIO_ACTIVE_HIGH>;
+            interrupts = <&gpio 124 IRQ_TYPE_EDGE_FALLING>;
+    
+            ports {
+                #address-cells = <0x01>;
+                #size-cells = <0x00>;
+    
+                port@0 {
+                    reg = <0x00>;
+                    dcon_rgb_in: endpoint {
+                        remote-endpoint = <&lcd0_rgb_out>;
+                    };
+                };
+    
+                port@1 {
+                    reg = <0x01>;
+                    dcon_gettl_out: endpoint {
+                        remote-endpoint = <&panel_dettl_in>;
+                    };
+                };
+            };
+        };
+    };
-- 
2.26.2

[RESEND PATCH v5 1/2] dt-bindings: display: himax, hx8837: Add Himax HX8837 bindings

[Lubomir Rintel]

Himax HX8837 is a secondary display controller used to drive the panel
on OLPC platforms.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Rob Herring <robh@kernel.org>

---
Changes since v4:
- Rob's Reviewed-by

Changes since v3:
- Moved to bindings/display/
- Added the ports
- Converted to YAML
- Removed Pavel's Ack, because the changes are substantial

Changes since v2:
- s/betweend/between/

Changes since v1:
- s/load-gpio/load-gpios/
- Use interrupt bindings instead of gpio for the IRQ

 .../bindings/display/bridge/himax,hx8837.yaml | 96 +++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/himax,hx8837.yaml

diff --git a/Documentation/devicetree/bindings/display/bridge/himax,hx8837.yaml b/Documentation/devicetree/bindings/display/bridge/himax,hx8837.yaml
new file mode 100644
index 0000000000000..f5b0a00f5089d
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/himax,hx8837.yaml
@@ -0,0 +1,96 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2018,2019,2020 Lubomir Rintel <lkundrak@v3.sk>
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/himax,hx8837.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: HX8837 Display Controller Device Tree Bindings
+
+maintainers:
+  - Lubomir Rintel <lkundrak@v3.sk>
+
+properties:
+  compatible:
+    const: himax,hx8837
+
+  reg:
+    const: 0xd
+
+  load-gpios:
+    maxItems: 1
+    description: GPIO specifier of DCON_LOAD pin (active high)
+
+  stat-gpios:
+    minItems: 2
+    description: GPIO specifier of DCON_STAT0 and DCON_STAT1 pins (active high)
+
+  interrupts:
+    maxItems: 1
+    description: Interrupt specifier of DCON_IRQ pin (edge falling)
+
+  ports:
+    type: object
+
+    properties:
+      port@0:
+        type: object
+        description: |
+          Video port for RGB input.
+
+      port@1:
+        type: object
+        description: |
+          Video port connected to the panel.
+
+    required:
+      - port@0
+      - port@1
+
+required:
+  - compatible
+  - reg
+  - load-gpios
+  - stat-gpios
+  - interrupts
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        
+        lcd-controller@d {
+            compatible = "himax,hx8837";
+            reg = <0x0d>;
+            stat-gpios = <&gpio 100 GPIO_ACTIVE_HIGH>,
+                         <&gpio 101 GPIO_ACTIVE_HIGH>;
+            load-gpios = <&gpio 142 GPIO_ACTIVE_HIGH>;
+            interrupts = <&gpio 124 IRQ_TYPE_EDGE_FALLING>;
+    
+            ports {
+                #address-cells = <0x01>;
+                #size-cells = <0x00>;
+    
+                port@0 {
+                    reg = <0x00>;
+                    dcon_rgb_in: endpoint {
+                        remote-endpoint = <&lcd0_rgb_out>;
+                    };
+                };
+    
+                port@1 {
+                    reg = <0x01>;
+                    dcon_gettl_out: endpoint {
+                        remote-endpoint = <&panel_dettl_in>;
+                    };
+                };
+            };
+        };
+    };
-- 
2.26.2

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[RESEND PATCH v5 2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

[Lubomir Rintel]

Himax HX8837 is used to drive the LCD panel on OLPC platforms.

It controls the panel backlight and is able to refresh it when the LCD
controller (and the rest of the plaform) is powered off.

It also converts regular RGB color data from the LCDC so that it looks
reasonable on the OLPC LCD panel with a monochromatic layer on top of a
layer that can either reflect light (b/w sunlight readable mode) or light
pattern of red, green and blue pixels.

At this point, the driver is rather basic. The self-refresh mode is not
supported. There's no way of independently controlling the color swizzling,
antialiasing or b/w conversion, but it probably isn't too useful either.

There's another driver for the same hardware on OLPC XO-1.5 and XO-1.75
in drivers/staging/olpc_dcon. The display on that hardware doesn't utilize
DRM, so this driver doesn't replace the other one yet.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>

---
Changes since v3:
- Added this patch, in place of a driver derived from
  drivers/staging/olpc_dcon. Compared to the previous one this
  implements the bare minimum, without the fancy stuff such as
  self-refresh that need more work/thinking.

 drivers/gpu/drm/bridge/Kconfig        |  13 ++
 drivers/gpu/drm/bridge/Makefile       |   1 +
 drivers/gpu/drm/bridge/himax-hx8837.c | 325 ++++++++++++++++++++++++++
 3 files changed, 339 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/himax-hx8837.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index ef91646441b16..6a923dd56c1d5 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -48,6 +48,19 @@ config DRM_DISPLAY_CONNECTOR
 	  on ARM-based platforms. Saying Y here when this driver is not needed
 	  will not cause any issue.
 
+config DRM_HIMAX_HX8837
+        tristate "HiMax HX8837 OLPC Display Controller"
+	depends on OF
+	depends on OLPC || ARCH_MMP || COMPILE_TEST
+	select DRM_KMS_HELPER
+        select BACKLIGHT_LCD_SUPPORT
+        select BACKLIGHT_CLASS_DEVICE
+        help
+          Enable support for HiMax HX8837 Display Controller as found in the
+          OLPC XO laptops.
+
+          If your laptop doesn't have green ears, say "N"
+
 config DRM_LONTIUM_LT9611
 	tristate "Lontium LT9611 DSI/HDMI bridge"
 	select SND_SOC_HDMI_CODEC if SND_SOC
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 2b3aff104e466..21f72df3260db 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -2,6 +2,7 @@
 obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
 obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
 obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
+obj-$(CONFIG_DRM_HIMAX_HX8837) += himax-hx8837.o
 obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
 obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
 obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
diff --git a/drivers/gpu/drm/bridge/himax-hx8837.c b/drivers/gpu/drm/bridge/himax-hx8837.c
new file mode 100644
index 0000000000000..1e97fcb8ce505
--- /dev/null
+++ b/drivers/gpu/drm/bridge/himax-hx8837.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HiMax HX8837 Display Controller Driver
+ *
+ * Datasheet: http://wiki.laptop.org/images/0/09/DCON_datasheet_HX8837-A.pdf
+ *
+ * Copyright (C) 2020 Lubomir Rintel
+ */
+
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_panel.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_of.h>
+#include <drm/drm_print.h>
+#include <drm/drm_probe_helper.h>
+
+#define bridge_to_hx8837_priv(x) \
+	container_of(x, struct hx8837_priv, bridge)
+
+/* DCON registers */
+enum {
+	DCON_REG_ID		= 0x00,
+	DCON_REG_MODE		= 0x01,
+	DCON_REG_HRES		= 0x02,
+	DCON_REG_HTOTAL		= 0x03,
+	DCON_REG_HSYNC_WIDTH	= 0x04,
+	DCON_REG_VRES		= 0x05,
+	DCON_REG_VTOTAL		= 0x06,
+	DCON_REG_VSYNC_WIDTH	= 0x07,
+	DCON_REG_TIMEOUT	= 0x08,
+	DCON_REG_SCAN_INT	= 0x09,
+	DCON_REG_BRIGHT		= 0x0a,
+	DCON_REG_MEM_OPT_A	= 0x41,
+	DCON_REG_MEM_OPT_B	= 0x42,
+};
+
+/* DCON_REG_MODE */
+enum {
+	MODE_PASSTHRU		= BIT(0),
+	MODE_SLEEP		= BIT(1),
+	MODE_SLEEP_AUTO		= BIT(2),
+	MODE_BL_ENABLE		= BIT(3),
+	MODE_BLANK		= BIT(4),
+	MODE_CSWIZZLE		= BIT(5),
+	MODE_COL_AA		= BIT(6),
+	MODE_MONO_LUMA		= BIT(7),
+	MODE_SCAN_INT		= BIT(8),
+	MODE_CLOCKDIV		= BIT(9),
+	MODE_DEBUG		= BIT(14),
+	MODE_SELFTEST		= BIT(15),
+};
+
+struct hx8837_priv {
+	struct regmap *regmap;
+	struct gpio_desc *load_gpio;
+
+	struct drm_bridge *panel_bridge;
+	struct drm_panel *panel;
+	struct drm_bridge bridge;
+};
+
+static int hx8837_bridge_attach(struct drm_bridge *bridge,
+				enum drm_bridge_attach_flags flags)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+
+	return drm_bridge_attach(bridge->encoder, priv->panel_bridge,
+				 bridge, flags);
+}
+
+static enum drm_mode_status hx8837_bridge_mode_valid(
+				struct drm_bridge *bridge,
+				const struct drm_display_info *info,
+				const struct drm_display_mode *mode)
+{
+	if (mode->hdisplay > 0xffff)
+		return MODE_BAD_HVALUE;
+	if (mode->htotal > 0xffff)
+		return MODE_BAD_HVALUE;
+	if (mode->hsync_start - mode->hdisplay > 0xff)
+		return MODE_HBLANK_WIDE;
+	if (mode->hsync_end - mode->hsync_start > 0xff)
+		return MODE_HSYNC_WIDE;
+	if (mode->vdisplay > 0xffff)
+		return MODE_BAD_VVALUE;
+	if (mode->vtotal > 0xffff)
+		return MODE_BAD_VVALUE;
+	if (mode->vsync_start - mode->vdisplay > 0xff)
+		return MODE_VBLANK_WIDE;
+	if (mode->vsync_end - mode->vsync_start > 0xff)
+		return MODE_VSYNC_WIDE;
+
+	return MODE_OK;
+}
+
+static void hx8837_bridge_disable(struct drm_bridge *bridge)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+	int ret;
+
+	ret = gpiod_direction_output(priv->load_gpio, 0);
+	if (ret)
+		DRM_ERROR("error enabling the dcon load: %d\n", ret);
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP);
+	if (ret)
+		DRM_ERROR("error disabling the dcon: %d\n", ret);
+}
+
+static void hx8837_bridge_enable(struct drm_bridge *bridge)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+	int ret;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP |
+					       MODE_SLEEP_AUTO |
+					       MODE_BLANK |
+					       MODE_SCAN_INT |
+					       MODE_CLOCKDIV |
+					       MODE_DEBUG |
+					       MODE_SELFTEST,
+					       MODE_PASSTHRU);
+	if (ret)
+		DRM_ERROR("error enabling the dcon: %d\n", ret);
+
+	ret = gpiod_direction_output(priv->load_gpio, 1);
+	if (ret)
+		DRM_ERROR("error enabling the dcon load: %d\n", ret);
+}
+
+static void hx8837_bridge_mode_set(struct drm_bridge *bridge,
+			   const struct drm_display_mode *mode,
+			   const struct drm_display_mode *adjusted_mode)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+
+	regmap_write(priv->regmap, DCON_REG_HRES, mode->hdisplay);
+	regmap_write(priv->regmap, DCON_REG_HTOTAL, mode->htotal);
+	regmap_write(priv->regmap, DCON_REG_HSYNC_WIDTH,
+			(mode->hsync_start - mode->hdisplay) << 8 |
+			(mode->hsync_end - mode->hsync_start));
+	regmap_write(priv->regmap, DCON_REG_VRES, mode->vdisplay);
+	regmap_write(priv->regmap, DCON_REG_VTOTAL, mode->vtotal);
+	regmap_write(priv->regmap, DCON_REG_VSYNC_WIDTH,
+			(mode->vsync_start - mode->vdisplay) << 8 |
+			(mode->vsync_end - mode->vsync_start));
+}
+
+static const struct drm_bridge_funcs hx8837_bridge_funcs = {
+	.attach = hx8837_bridge_attach,
+	.mode_valid = hx8837_bridge_mode_valid,
+	.disable = hx8837_bridge_disable,
+	.enable = hx8837_bridge_enable,
+	.mode_set = hx8837_bridge_mode_set,
+};
+
+static int hx8837_bl_update_status(struct backlight_device *bl)
+{
+	struct hx8837_priv *priv = bl_get_data(bl);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
+					       0x000f,
+					       bl->props.brightness);
+	if (ret) {
+		dev_err(&bl->dev, "error setting the backlight: %d\n", ret);
+		return ret;
+	}
+
+	if (bl->props.brightness)
+		val = MODE_CSWIZZLE | MODE_COL_AA;
+	else
+		val = MODE_MONO_LUMA;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_CSWIZZLE |
+					       MODE_COL_AA |
+					       MODE_MONO_LUMA,
+					       val);
+	if (ret) {
+		dev_err(&bl->dev, "error setting color mode: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct backlight_ops hx8837_bl_ops = {
+	.update_status = hx8837_bl_update_status,
+};
+
+static const struct regmap_config hx8837_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 0x4c,
+	.val_format_endian = REGMAP_ENDIAN_LITTLE,
+};
+
+static int hx8837_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct backlight_properties bl_props = {
+		.type = BACKLIGHT_RAW,
+		.max_brightness = 0xf,
+	};
+	struct device *dev = &client->dev;
+	struct backlight_device *bl;
+	struct hx8837_priv *priv;
+	unsigned int val;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, priv);
+
+	priv->load_gpio = devm_gpiod_get(dev, "load", GPIOD_ASIS);
+	if (IS_ERR(priv->load_gpio))
+		return PTR_ERR(priv->load_gpio);
+
+	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1,
+					  &priv->panel, NULL);
+	if (ret)
+		return ret;
+
+	if (priv->panel->backlight) {
+		dev_err(dev, "the panel already has a backlight controller\n");
+		return -ENODEV;
+	}
+
+	priv->panel_bridge = devm_drm_panel_bridge_add(dev, priv->panel);
+	if (IS_ERR(priv->panel_bridge))
+		return PTR_ERR(priv->panel_bridge);
+
+	priv->regmap = devm_regmap_init_i2c(client, &hx8837_regmap_config);
+	if (IS_ERR(priv->regmap)) {
+		dev_err(dev, "regmap init failed\n");
+		return PTR_ERR(priv->regmap);
+	}
+
+	ret = regmap_read(priv->regmap, DCON_REG_ID, &val);
+	if (ret < 0) {
+		dev_err(dev, "error reading the model id: %d\n", ret);
+		return ret;
+	}
+	if ((val & 0xff00) != 0xdc00) {
+		dev_err(dev, "the device is not a hx8837\n");
+		return -ENODEV;
+	}
+
+	ret = regmap_read(priv->regmap, DCON_REG_BRIGHT, &val);
+	if (ret < 0) {
+		dev_err(&bl->dev, "error getting the backlight: %d\n", ret);
+		return ret;
+	}
+	bl_props.brightness = val & 0xf;
+
+	bl = devm_backlight_device_register(dev, dev_name(dev), dev, priv,
+					    &hx8837_bl_ops, &bl_props);
+	if (IS_ERR(bl)) {
+		dev_err(dev, "failed to register backlight\n");
+		return PTR_ERR(bl);
+	}
+
+	priv->panel->backlight = bl;
+
+	INIT_LIST_HEAD(&priv->bridge.list);
+	priv->bridge.funcs = &hx8837_bridge_funcs;
+	priv->bridge.of_node = dev->of_node;
+	drm_bridge_add(&priv->bridge);
+
+	dev_info(dev, "HiMax HX8837 Display Controller Driver\n");
+	return 0;
+}
+
+static int hx8837_remove(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	drm_bridge_remove(&priv->bridge);
+	priv->panel->backlight = NULL;
+
+	return 0;
+}
+
+static const struct of_device_id hx8837_dt_ids[] = {
+	{ .compatible = "himax,hx8837", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
+
+static const struct i2c_device_id hx8837_ids[] = {
+	{ "hx8837", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, hx8837_ids);
+
+static struct i2c_driver hx8837_driver = {
+	.probe = hx8837_probe,
+	.remove = hx8837_remove,
+	.driver = {
+		.name = "hx8837",
+		.of_match_table = of_match_ptr(hx8837_dt_ids),
+	},
+	.id_table = hx8837_ids,
+};
+
+module_i2c_driver(hx8837_driver);
+
+MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
+MODULE_DESCRIPTION("HiMax HX8837 Display Controller Driver");
+MODULE_LICENSE("GPL");
-- 
2.26.2

[RESEND PATCH v5 2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

[Lubomir Rintel]

Himax HX8837 is used to drive the LCD panel on OLPC platforms.

It controls the panel backlight and is able to refresh it when the LCD
controller (and the rest of the plaform) is powered off.

It also converts regular RGB color data from the LCDC so that it looks
reasonable on the OLPC LCD panel with a monochromatic layer on top of a
layer that can either reflect light (b/w sunlight readable mode) or light
pattern of red, green and blue pixels.

At this point, the driver is rather basic. The self-refresh mode is not
supported. There's no way of independently controlling the color swizzling,
antialiasing or b/w conversion, but it probably isn't too useful either.

There's another driver for the same hardware on OLPC XO-1.5 and XO-1.75
in drivers/staging/olpc_dcon. The display on that hardware doesn't utilize
DRM, so this driver doesn't replace the other one yet.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>

---
Changes since v3:
- Added this patch, in place of a driver derived from
  drivers/staging/olpc_dcon. Compared to the previous one this
  implements the bare minimum, without the fancy stuff such as
  self-refresh that need more work/thinking.

 drivers/gpu/drm/bridge/Kconfig        |  13 ++
 drivers/gpu/drm/bridge/Makefile       |   1 +
 drivers/gpu/drm/bridge/himax-hx8837.c | 325 ++++++++++++++++++++++++++
 3 files changed, 339 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/himax-hx8837.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index ef91646441b16..6a923dd56c1d5 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -48,6 +48,19 @@ config DRM_DISPLAY_CONNECTOR
 	  on ARM-based platforms. Saying Y here when this driver is not needed
 	  will not cause any issue.
 
+config DRM_HIMAX_HX8837
+        tristate "HiMax HX8837 OLPC Display Controller"
+	depends on OF
+	depends on OLPC || ARCH_MMP || COMPILE_TEST
+	select DRM_KMS_HELPER
+        select BACKLIGHT_LCD_SUPPORT
+        select BACKLIGHT_CLASS_DEVICE
+        help
+          Enable support for HiMax HX8837 Display Controller as found in the
+          OLPC XO laptops.
+
+          If your laptop doesn't have green ears, say "N"
+
 config DRM_LONTIUM_LT9611
 	tristate "Lontium LT9611 DSI/HDMI bridge"
 	select SND_SOC_HDMI_CODEC if SND_SOC
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 2b3aff104e466..21f72df3260db 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -2,6 +2,7 @@
 obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
 obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
 obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
+obj-$(CONFIG_DRM_HIMAX_HX8837) += himax-hx8837.o
 obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
 obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
 obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
diff --git a/drivers/gpu/drm/bridge/himax-hx8837.c b/drivers/gpu/drm/bridge/himax-hx8837.c
new file mode 100644
index 0000000000000..1e97fcb8ce505
--- /dev/null
+++ b/drivers/gpu/drm/bridge/himax-hx8837.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HiMax HX8837 Display Controller Driver
+ *
+ * Datasheet: http://wiki.laptop.org/images/0/09/DCON_datasheet_HX8837-A.pdf
+ *
+ * Copyright (C) 2020 Lubomir Rintel
+ */
+
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_panel.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_of.h>
+#include <drm/drm_print.h>
+#include <drm/drm_probe_helper.h>
+
+#define bridge_to_hx8837_priv(x) \
+	container_of(x, struct hx8837_priv, bridge)
+
+/* DCON registers */
+enum {
+	DCON_REG_ID		= 0x00,
+	DCON_REG_MODE		= 0x01,
+	DCON_REG_HRES		= 0x02,
+	DCON_REG_HTOTAL		= 0x03,
+	DCON_REG_HSYNC_WIDTH	= 0x04,
+	DCON_REG_VRES		= 0x05,
+	DCON_REG_VTOTAL		= 0x06,
+	DCON_REG_VSYNC_WIDTH	= 0x07,
+	DCON_REG_TIMEOUT	= 0x08,
+	DCON_REG_SCAN_INT	= 0x09,
+	DCON_REG_BRIGHT		= 0x0a,
+	DCON_REG_MEM_OPT_A	= 0x41,
+	DCON_REG_MEM_OPT_B	= 0x42,
+};
+
+/* DCON_REG_MODE */
+enum {
+	MODE_PASSTHRU		= BIT(0),
+	MODE_SLEEP		= BIT(1),
+	MODE_SLEEP_AUTO		= BIT(2),
+	MODE_BL_ENABLE		= BIT(3),
+	MODE_BLANK		= BIT(4),
+	MODE_CSWIZZLE		= BIT(5),
+	MODE_COL_AA		= BIT(6),
+	MODE_MONO_LUMA		= BIT(7),
+	MODE_SCAN_INT		= BIT(8),
+	MODE_CLOCKDIV		= BIT(9),
+	MODE_DEBUG		= BIT(14),
+	MODE_SELFTEST		= BIT(15),
+};
+
+struct hx8837_priv {
+	struct regmap *regmap;
+	struct gpio_desc *load_gpio;
+
+	struct drm_bridge *panel_bridge;
+	struct drm_panel *panel;
+	struct drm_bridge bridge;
+};
+
+static int hx8837_bridge_attach(struct drm_bridge *bridge,
+				enum drm_bridge_attach_flags flags)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+
+	return drm_bridge_attach(bridge->encoder, priv->panel_bridge,
+				 bridge, flags);
+}
+
+static enum drm_mode_status hx8837_bridge_mode_valid(
+				struct drm_bridge *bridge,
+				const struct drm_display_info *info,
+				const struct drm_display_mode *mode)
+{
+	if (mode->hdisplay > 0xffff)
+		return MODE_BAD_HVALUE;
+	if (mode->htotal > 0xffff)
+		return MODE_BAD_HVALUE;
+	if (mode->hsync_start - mode->hdisplay > 0xff)
+		return MODE_HBLANK_WIDE;
+	if (mode->hsync_end - mode->hsync_start > 0xff)
+		return MODE_HSYNC_WIDE;
+	if (mode->vdisplay > 0xffff)
+		return MODE_BAD_VVALUE;
+	if (mode->vtotal > 0xffff)
+		return MODE_BAD_VVALUE;
+	if (mode->vsync_start - mode->vdisplay > 0xff)
+		return MODE_VBLANK_WIDE;
+	if (mode->vsync_end - mode->vsync_start > 0xff)
+		return MODE_VSYNC_WIDE;
+
+	return MODE_OK;
+}
+
+static void hx8837_bridge_disable(struct drm_bridge *bridge)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+	int ret;
+
+	ret = gpiod_direction_output(priv->load_gpio, 0);
+	if (ret)
+		DRM_ERROR("error enabling the dcon load: %d\n", ret);
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP);
+	if (ret)
+		DRM_ERROR("error disabling the dcon: %d\n", ret);
+}
+
+static void hx8837_bridge_enable(struct drm_bridge *bridge)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+	int ret;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP |
+					       MODE_SLEEP_AUTO |
+					       MODE_BLANK |
+					       MODE_SCAN_INT |
+					       MODE_CLOCKDIV |
+					       MODE_DEBUG |
+					       MODE_SELFTEST,
+					       MODE_PASSTHRU);
+	if (ret)
+		DRM_ERROR("error enabling the dcon: %d\n", ret);
+
+	ret = gpiod_direction_output(priv->load_gpio, 1);
+	if (ret)
+		DRM_ERROR("error enabling the dcon load: %d\n", ret);
+}
+
+static void hx8837_bridge_mode_set(struct drm_bridge *bridge,
+			   const struct drm_display_mode *mode,
+			   const struct drm_display_mode *adjusted_mode)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+
+	regmap_write(priv->regmap, DCON_REG_HRES, mode->hdisplay);
+	regmap_write(priv->regmap, DCON_REG_HTOTAL, mode->htotal);
+	regmap_write(priv->regmap, DCON_REG_HSYNC_WIDTH,
+			(mode->hsync_start - mode->hdisplay) << 8 |
+			(mode->hsync_end - mode->hsync_start));
+	regmap_write(priv->regmap, DCON_REG_VRES, mode->vdisplay);
+	regmap_write(priv->regmap, DCON_REG_VTOTAL, mode->vtotal);
+	regmap_write(priv->regmap, DCON_REG_VSYNC_WIDTH,
+			(mode->vsync_start - mode->vdisplay) << 8 |
+			(mode->vsync_end - mode->vsync_start));
+}
+
+static const struct drm_bridge_funcs hx8837_bridge_funcs = {
+	.attach = hx8837_bridge_attach,
+	.mode_valid = hx8837_bridge_mode_valid,
+	.disable = hx8837_bridge_disable,
+	.enable = hx8837_bridge_enable,
+	.mode_set = hx8837_bridge_mode_set,
+};
+
+static int hx8837_bl_update_status(struct backlight_device *bl)
+{
+	struct hx8837_priv *priv = bl_get_data(bl);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
+					       0x000f,
+					       bl->props.brightness);
+	if (ret) {
+		dev_err(&bl->dev, "error setting the backlight: %d\n", ret);
+		return ret;
+	}
+
+	if (bl->props.brightness)
+		val = MODE_CSWIZZLE | MODE_COL_AA;
+	else
+		val = MODE_MONO_LUMA;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_CSWIZZLE |
+					       MODE_COL_AA |
+					       MODE_MONO_LUMA,
+					       val);
+	if (ret) {
+		dev_err(&bl->dev, "error setting color mode: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct backlight_ops hx8837_bl_ops = {
+	.update_status = hx8837_bl_update_status,
+};
+
+static const struct regmap_config hx8837_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 0x4c,
+	.val_format_endian = REGMAP_ENDIAN_LITTLE,
+};
+
+static int hx8837_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct backlight_properties bl_props = {
+		.type = BACKLIGHT_RAW,
+		.max_brightness = 0xf,
+	};
+	struct device *dev = &client->dev;
+	struct backlight_device *bl;
+	struct hx8837_priv *priv;
+	unsigned int val;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, priv);
+
+	priv->load_gpio = devm_gpiod_get(dev, "load", GPIOD_ASIS);
+	if (IS_ERR(priv->load_gpio))
+		return PTR_ERR(priv->load_gpio);
+
+	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1,
+					  &priv->panel, NULL);
+	if (ret)
+		return ret;
+
+	if (priv->panel->backlight) {
+		dev_err(dev, "the panel already has a backlight controller\n");
+		return -ENODEV;
+	}
+
+	priv->panel_bridge = devm_drm_panel_bridge_add(dev, priv->panel);
+	if (IS_ERR(priv->panel_bridge))
+		return PTR_ERR(priv->panel_bridge);
+
+	priv->regmap = devm_regmap_init_i2c(client, &hx8837_regmap_config);
+	if (IS_ERR(priv->regmap)) {
+		dev_err(dev, "regmap init failed\n");
+		return PTR_ERR(priv->regmap);
+	}
+
+	ret = regmap_read(priv->regmap, DCON_REG_ID, &val);
+	if (ret < 0) {
+		dev_err(dev, "error reading the model id: %d\n", ret);
+		return ret;
+	}
+	if ((val & 0xff00) != 0xdc00) {
+		dev_err(dev, "the device is not a hx8837\n");
+		return -ENODEV;
+	}
+
+	ret = regmap_read(priv->regmap, DCON_REG_BRIGHT, &val);
+	if (ret < 0) {
+		dev_err(&bl->dev, "error getting the backlight: %d\n", ret);
+		return ret;
+	}
+	bl_props.brightness = val & 0xf;
+
+	bl = devm_backlight_device_register(dev, dev_name(dev), dev, priv,
+					    &hx8837_bl_ops, &bl_props);
+	if (IS_ERR(bl)) {
+		dev_err(dev, "failed to register backlight\n");
+		return PTR_ERR(bl);
+	}
+
+	priv->panel->backlight = bl;
+
+	INIT_LIST_HEAD(&priv->bridge.list);
+	priv->bridge.funcs = &hx8837_bridge_funcs;
+	priv->bridge.of_node = dev->of_node;
+	drm_bridge_add(&priv->bridge);
+
+	dev_info(dev, "HiMax HX8837 Display Controller Driver\n");
+	return 0;
+}
+
+static int hx8837_remove(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	drm_bridge_remove(&priv->bridge);
+	priv->panel->backlight = NULL;
+
+	return 0;
+}
+
+static const struct of_device_id hx8837_dt_ids[] = {
+	{ .compatible = "himax,hx8837", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
+
+static const struct i2c_device_id hx8837_ids[] = {
+	{ "hx8837", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, hx8837_ids);
+
+static struct i2c_driver hx8837_driver = {
+	.probe = hx8837_probe,
+	.remove = hx8837_remove,
+	.driver = {
+		.name = "hx8837",
+		.of_match_table = of_match_ptr(hx8837_dt_ids),
+	},
+	.id_table = hx8837_ids,
+};
+
+module_i2c_driver(hx8837_driver);
+
+MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
+MODULE_DESCRIPTION("HiMax HX8837 Display Controller Driver");
+MODULE_LICENSE("GPL");
-- 
2.26.2

_______________________________________________
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dri-devel@lists.freedesktop.org
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Re: [RESEND PATCH v5 2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

[Sam Ravnborg]

Hi Lubomir.

On Sat, Sep 26, 2020 at 02:07:19AM +0200, Lubomir Rintel wrote:
> Himax HX8837 is used to drive the LCD panel on OLPC platforms.
> 
> It controls the panel backlight and is able to refresh it when the LCD
> controller (and the rest of the plaform) is powered off.
> 
> It also converts regular RGB color data from the LCDC so that it looks
> reasonable on the OLPC LCD panel with a monochromatic layer on top of a
> layer that can either reflect light (b/w sunlight readable mode) or light
> pattern of red, green and blue pixels.
> 
> At this point, the driver is rather basic. The self-refresh mode is not
> supported. There's no way of independently controlling the color swizzling,
> antialiasing or b/w conversion, but it probably isn't too useful either.
> 
> There's another driver for the same hardware on OLPC XO-1.5 and XO-1.75
> in drivers/staging/olpc_dcon. The display on that hardware doesn't utilize
> DRM, so this driver doesn't replace the other one yet.
> 
> Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>

A little feedback follows.

	Sam

> 
> ---
> Changes since v3:
> - Added this patch, in place of a driver derived from
>   drivers/staging/olpc_dcon. Compared to the previous one this
>   implements the bare minimum, without the fancy stuff such as
>   self-refresh that need more work/thinking.
> 
>  drivers/gpu/drm/bridge/Kconfig        |  13 ++
>  drivers/gpu/drm/bridge/Makefile       |   1 +
>  drivers/gpu/drm/bridge/himax-hx8837.c | 325 ++++++++++++++++++++++++++
>  3 files changed, 339 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/himax-hx8837.c
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index ef91646441b16..6a923dd56c1d5 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -48,6 +48,19 @@ config DRM_DISPLAY_CONNECTOR
>  	  on ARM-based platforms. Saying Y here when this driver is not needed
>  	  will not cause any issue.
>  
> +config DRM_HIMAX_HX8837
> +        tristate "HiMax HX8837 OLPC Display Controller"
> +	depends on OF
> +	depends on OLPC || ARCH_MMP || COMPILE_TEST
> +	select DRM_KMS_HELPER
> +        select BACKLIGHT_LCD_SUPPORT
> +        select BACKLIGHT_CLASS_DEVICE
> +        help
> +          Enable support for HiMax HX8837 Display Controller as found in the
> +          OLPC XO laptops.
> +
> +          If your laptop doesn't have green ears, say "N"

There is a mixture of tabs and spaces for indent - use tabs only (and
tabs + 2 spaces for the help text).


> +
>  config DRM_LONTIUM_LT9611
>  	tristate "Lontium LT9611 DSI/HDMI bridge"
>  	select SND_SOC_HDMI_CODEC if SND_SOC
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 2b3aff104e466..21f72df3260db 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -2,6 +2,7 @@
>  obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
>  obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
>  obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
> +obj-$(CONFIG_DRM_HIMAX_HX8837) += himax-hx8837.o
Please add in alphabetical order.

>  obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
>  obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
>  obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
> diff --git a/drivers/gpu/drm/bridge/himax-hx8837.c b/drivers/gpu/drm/bridge/himax-hx8837.c
> new file mode 100644
> index 0000000000000..1e97fcb8ce505
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/himax-hx8837.c
> @@ -0,0 +1,325 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * HiMax HX8837 Display Controller Driver
> + *
> + * Datasheet: http://wiki.laptop.org/images/0/09/DCON_datasheet_HX8837-A.pdf
> + *
> + * Copyright (C) 2020 Lubomir Rintel
> + */
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_panel.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_of.h>
> +#include <drm/drm_print.h>
> +#include <drm/drm_probe_helper.h>
In blocks are good but please add them in alphabetical order.

> +
> +#define bridge_to_hx8837_priv(x) \
> +	container_of(x, struct hx8837_priv, bridge)
> +
> +/* DCON registers */
> +enum {
> +	DCON_REG_ID		= 0x00,
> +	DCON_REG_MODE		= 0x01,
> +	DCON_REG_HRES		= 0x02,
> +	DCON_REG_HTOTAL		= 0x03,
> +	DCON_REG_HSYNC_WIDTH	= 0x04,
> +	DCON_REG_VRES		= 0x05,
> +	DCON_REG_VTOTAL		= 0x06,
> +	DCON_REG_VSYNC_WIDTH	= 0x07,
> +	DCON_REG_TIMEOUT	= 0x08,
> +	DCON_REG_SCAN_INT	= 0x09,
> +	DCON_REG_BRIGHT		= 0x0a,
> +	DCON_REG_MEM_OPT_A	= 0x41,
> +	DCON_REG_MEM_OPT_B	= 0x42,
> +};
> +
> +/* DCON_REG_MODE */
> +enum {
> +	MODE_PASSTHRU		= BIT(0),
> +	MODE_SLEEP		= BIT(1),
> +	MODE_SLEEP_AUTO		= BIT(2),
> +	MODE_BL_ENABLE		= BIT(3),
> +	MODE_BLANK		= BIT(4),
> +	MODE_CSWIZZLE		= BIT(5),
> +	MODE_COL_AA		= BIT(6),
> +	MODE_MONO_LUMA		= BIT(7),
> +	MODE_SCAN_INT		= BIT(8),
> +	MODE_CLOCKDIV		= BIT(9),
> +	MODE_DEBUG		= BIT(14),
> +	MODE_SELFTEST		= BIT(15),
> +};
> +
> +struct hx8837_priv {
> +	struct regmap *regmap;
> +	struct gpio_desc *load_gpio;
> +
> +	struct drm_bridge *panel_bridge;
> +	struct drm_panel *panel;
No need for the panel pointer - use a local variable in the probe
function 

> +	struct drm_bridge bridge;
> +};
> +
> +static int hx8837_bridge_attach(struct drm_bridge *bridge,
> +				enum drm_bridge_attach_flags flags)
> +{
> +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> +
> +	return drm_bridge_attach(bridge->encoder, priv->panel_bridge,
> +				 bridge, flags);
> +}
> +
> +static enum drm_mode_status hx8837_bridge_mode_valid(
> +				struct drm_bridge *bridge,
> +				const struct drm_display_info *info,
> +				const struct drm_display_mode *mode)
> +{
> +	if (mode->hdisplay > 0xffff)
> +		return MODE_BAD_HVALUE;
> +	if (mode->htotal > 0xffff)
> +		return MODE_BAD_HVALUE;
> +	if (mode->hsync_start - mode->hdisplay > 0xff)
> +		return MODE_HBLANK_WIDE;
> +	if (mode->hsync_end - mode->hsync_start > 0xff)
> +		return MODE_HSYNC_WIDE;
> +	if (mode->vdisplay > 0xffff)
> +		return MODE_BAD_VVALUE;
> +	if (mode->vtotal > 0xffff)
> +		return MODE_BAD_VVALUE;
> +	if (mode->vsync_start - mode->vdisplay > 0xff)
> +		return MODE_VBLANK_WIDE;
> +	if (mode->vsync_end - mode->vsync_start > 0xff)
> +		return MODE_VSYNC_WIDE;
> +
> +	return MODE_OK;
> +}
> +
> +static void hx8837_bridge_disable(struct drm_bridge *bridge)
> +{
> +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> +	int ret;
> +
> +	ret = gpiod_direction_output(priv->load_gpio, 0);
> +	if (ret)
> +		DRM_ERROR("error enabling the dcon load: %d\n", ret);
The driver uses both dev_xxx() and DRM_XXX for logging.
Please stick to one way to do logging - I prefer for bridge drivers
the dev_* variants.

> +
> +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> +					       MODE_PASSTHRU |
> +					       MODE_SLEEP,
> +					       MODE_PASSTHRU |
> +					       MODE_SLEEP);
> +	if (ret)
> +		DRM_ERROR("error disabling the dcon: %d\n", ret);
> +}
> +
> +static void hx8837_bridge_enable(struct drm_bridge *bridge)
> +{
> +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> +	int ret;
> +
> +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> +					       MODE_PASSTHRU |
> +					       MODE_SLEEP |
> +					       MODE_SLEEP_AUTO |
> +					       MODE_BLANK |
> +					       MODE_SCAN_INT |
> +					       MODE_CLOCKDIV |
> +					       MODE_DEBUG |
> +					       MODE_SELFTEST,
> +					       MODE_PASSTHRU);
> +	if (ret)
> +		DRM_ERROR("error enabling the dcon: %d\n", ret);
> +
> +	ret = gpiod_direction_output(priv->load_gpio, 1);
> +	if (ret)
> +		DRM_ERROR("error enabling the dcon load: %d\n", ret);
> +}
> +
> +static void hx8837_bridge_mode_set(struct drm_bridge *bridge,
> +			   const struct drm_display_mode *mode,
> +			   const struct drm_display_mode *adjusted_mode)
> +{
> +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> +
> +	regmap_write(priv->regmap, DCON_REG_HRES, mode->hdisplay);
> +	regmap_write(priv->regmap, DCON_REG_HTOTAL, mode->htotal);
> +	regmap_write(priv->regmap, DCON_REG_HSYNC_WIDTH,
> +			(mode->hsync_start - mode->hdisplay) << 8 |
> +			(mode->hsync_end - mode->hsync_start));
> +	regmap_write(priv->regmap, DCON_REG_VRES, mode->vdisplay);
> +	regmap_write(priv->regmap, DCON_REG_VTOTAL, mode->vtotal);
> +	regmap_write(priv->regmap, DCON_REG_VSYNC_WIDTH,
> +			(mode->vsync_start - mode->vdisplay) << 8 |
> +			(mode->vsync_end - mode->vsync_start));
> +}
> +
> +static const struct drm_bridge_funcs hx8837_bridge_funcs = {
> +	.attach = hx8837_bridge_attach,
> +	.mode_valid = hx8837_bridge_mode_valid,
> +	.disable = hx8837_bridge_disable,
> +	.enable = hx8837_bridge_enable,
> +	.mode_set = hx8837_bridge_mode_set,
> +};
> +
> +static int hx8837_bl_update_status(struct backlight_device *bl)
> +{
> +	struct hx8837_priv *priv = bl_get_data(bl);
> +	unsigned int val;
> +	int ret;
> +
> +	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
> +					       0x000f,
> +					       bl->props.brightness);

Use backlight_get_brightness() to get the brightness.
This will also make sure 0 is returned when backlight is off so the
logic a few lines down is correct.

> +	if (ret) {
> +		dev_err(&bl->dev, "error setting the backlight: %d\n", ret);
> +		return ret;
> +	}
> +
> +	if (bl->props.brightness)
> +		val = MODE_CSWIZZLE | MODE_COL_AA;
> +	else
> +		val = MODE_MONO_LUMA;
> +
> +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> +					       MODE_CSWIZZLE |
> +					       MODE_COL_AA |
> +					       MODE_MONO_LUMA,
> +					       val);
> +	if (ret) {
> +		dev_err(&bl->dev, "error setting color mode: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct backlight_ops hx8837_bl_ops = {
> +	.update_status = hx8837_bl_update_status,
> +};
> +
> +static const struct regmap_config hx8837_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +	.max_register = 0x4c,
> +	.val_format_endian = REGMAP_ENDIAN_LITTLE,
> +};
> +
> +static int hx8837_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct backlight_properties bl_props = {
> +		.type = BACKLIGHT_RAW,
> +		.max_brightness = 0xf,
> +	};
Make it const
Maybe use a constant for the max value as it is also used as a mask
later.

> +	struct device *dev = &client->dev;
> +	struct backlight_device *bl;
> +	struct hx8837_priv *priv;
> +	unsigned int val;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, priv);
> +
> +	priv->load_gpio = devm_gpiod_get(dev, "load", GPIOD_ASIS);
> +	if (IS_ERR(priv->load_gpio))
> +		return PTR_ERR(priv->load_gpio);
> +
> +	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1,
> +					  &priv->panel, NULL);
> +	if (ret)
> +		return ret;
> +
> +	if (priv->panel->backlight) {
> +		dev_err(dev, "the panel already has a backlight controller\n");
> +		return -ENODEV;
> +	}
> +
> +	priv->panel_bridge = devm_drm_panel_bridge_add(dev, priv->panel);
> +	if (IS_ERR(priv->panel_bridge))
> +		return PTR_ERR(priv->panel_bridge);
> +
> +	priv->regmap = devm_regmap_init_i2c(client, &hx8837_regmap_config);
> +	if (IS_ERR(priv->regmap)) {
> +		dev_err(dev, "regmap init failed\n");
> +		return PTR_ERR(priv->regmap);
> +	}
> +
> +	ret = regmap_read(priv->regmap, DCON_REG_ID, &val);
> +	if (ret < 0) {
> +		dev_err(dev, "error reading the model id: %d\n", ret);
> +		return ret;
> +	}
> +	if ((val & 0xff00) != 0xdc00) {
> +		dev_err(dev, "the device is not a hx8837\n");
> +		return -ENODEV;
> +	}
> +
> +	ret = regmap_read(priv->regmap, DCON_REG_BRIGHT, &val);
> +	if (ret < 0) {
> +		dev_err(&bl->dev, "error getting the backlight: %d\n", ret);
> +		return ret;
> +	}
> +	bl_props.brightness = val & 0xf;
> +
> +	bl = devm_backlight_device_register(dev, dev_name(dev), dev, priv,
> +					    &hx8837_bl_ops, &bl_props);
> +	if (IS_ERR(bl)) {
> +		dev_err(dev, "failed to register backlight\n");
> +		return PTR_ERR(bl);
> +	}
> +
> +	priv->panel->backlight = bl;
> +
> +	INIT_LIST_HEAD(&priv->bridge.list);
> +	priv->bridge.funcs = &hx8837_bridge_funcs;
> +	priv->bridge.of_node = dev->of_node;
> +	drm_bridge_add(&priv->bridge);
> +
> +	dev_info(dev, "HiMax HX8837 Display Controller Driver\n");
> +	return 0;
> +}
> +
> +static int hx8837_remove(struct i2c_client *client)
> +{
> +	struct device *dev = &client->dev;
> +	struct hx8837_priv *priv = dev_get_drvdata(dev);
> +
> +	drm_bridge_remove(&priv->bridge);

> +	priv->panel->backlight = NULL;
I cannot see why this is needed.
IF this is needed we have a bug in the core stuff we need to fix.

> +
> +	return 0;
> +}
> +
> +static const struct of_device_id hx8837_dt_ids[] = {
> +	{ .compatible = "himax,hx8837", },
> +	{ }
We often see { /* sentinel */ },
in these cases.

> +};
> +MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
> +
> +static const struct i2c_device_id hx8837_ids[] = {
> +	{ "hx8837", 0 },
> +	{ }
Likewise

> +};
> +MODULE_DEVICE_TABLE(i2c, hx8837_ids);
> +
> +static struct i2c_driver hx8837_driver = {
> +	.probe = hx8837_probe,
> +	.remove = hx8837_remove,
> +	.driver = {
> +		.name = "hx8837",
> +		.of_match_table = of_match_ptr(hx8837_dt_ids),
> +	},
> +	.id_table = hx8837_ids,
> +};
> +
> +module_i2c_driver(hx8837_driver);
> +
> +MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
> +MODULE_DESCRIPTION("HiMax HX8837 Display Controller Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.26.2
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [RESEND PATCH v5 2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

[Sam Ravnborg]

Hi Lubomir.

On Sat, Sep 26, 2020 at 02:07:19AM +0200, Lubomir Rintel wrote:
> Himax HX8837 is used to drive the LCD panel on OLPC platforms.
> 
> It controls the panel backlight and is able to refresh it when the LCD
> controller (and the rest of the plaform) is powered off.
> 
> It also converts regular RGB color data from the LCDC so that it looks
> reasonable on the OLPC LCD panel with a monochromatic layer on top of a
> layer that can either reflect light (b/w sunlight readable mode) or light
> pattern of red, green and blue pixels.
> 
> At this point, the driver is rather basic. The self-refresh mode is not
> supported. There's no way of independently controlling the color swizzling,
> antialiasing or b/w conversion, but it probably isn't too useful either.
> 
> There's another driver for the same hardware on OLPC XO-1.5 and XO-1.75
> in drivers/staging/olpc_dcon. The display on that hardware doesn't utilize
> DRM, so this driver doesn't replace the other one yet.
> 
> Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>

A little feedback follows.

	Sam

> 
> ---
> Changes since v3:
> - Added this patch, in place of a driver derived from
>   drivers/staging/olpc_dcon. Compared to the previous one this
>   implements the bare minimum, without the fancy stuff such as
>   self-refresh that need more work/thinking.
> 
>  drivers/gpu/drm/bridge/Kconfig        |  13 ++
>  drivers/gpu/drm/bridge/Makefile       |   1 +
>  drivers/gpu/drm/bridge/himax-hx8837.c | 325 ++++++++++++++++++++++++++
>  3 files changed, 339 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/himax-hx8837.c
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index ef91646441b16..6a923dd56c1d5 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -48,6 +48,19 @@ config DRM_DISPLAY_CONNECTOR
>  	  on ARM-based platforms. Saying Y here when this driver is not needed
>  	  will not cause any issue.
>  
> +config DRM_HIMAX_HX8837
> +        tristate "HiMax HX8837 OLPC Display Controller"
> +	depends on OF
> +	depends on OLPC || ARCH_MMP || COMPILE_TEST
> +	select DRM_KMS_HELPER
> +        select BACKLIGHT_LCD_SUPPORT
> +        select BACKLIGHT_CLASS_DEVICE
> +        help
> +          Enable support for HiMax HX8837 Display Controller as found in the
> +          OLPC XO laptops.
> +
> +          If your laptop doesn't have green ears, say "N"

There is a mixture of tabs and spaces for indent - use tabs only (and
tabs + 2 spaces for the help text).


> +
>  config DRM_LONTIUM_LT9611
>  	tristate "Lontium LT9611 DSI/HDMI bridge"
>  	select SND_SOC_HDMI_CODEC if SND_SOC
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 2b3aff104e466..21f72df3260db 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -2,6 +2,7 @@
>  obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
>  obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
>  obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
> +obj-$(CONFIG_DRM_HIMAX_HX8837) += himax-hx8837.o
Please add in alphabetical order.

>  obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
>  obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
>  obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
> diff --git a/drivers/gpu/drm/bridge/himax-hx8837.c b/drivers/gpu/drm/bridge/himax-hx8837.c
> new file mode 100644
> index 0000000000000..1e97fcb8ce505
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/himax-hx8837.c
> @@ -0,0 +1,325 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * HiMax HX8837 Display Controller Driver
> + *
> + * Datasheet: http://wiki.laptop.org/images/0/09/DCON_datasheet_HX8837-A.pdf
> + *
> + * Copyright (C) 2020 Lubomir Rintel
> + */
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_panel.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_of.h>
> +#include <drm/drm_print.h>
> +#include <drm/drm_probe_helper.h>
In blocks are good but please add them in alphabetical order.

> +
> +#define bridge_to_hx8837_priv(x) \
> +	container_of(x, struct hx8837_priv, bridge)
> +
> +/* DCON registers */
> +enum {
> +	DCON_REG_ID		= 0x00,
> +	DCON_REG_MODE		= 0x01,
> +	DCON_REG_HRES		= 0x02,
> +	DCON_REG_HTOTAL		= 0x03,
> +	DCON_REG_HSYNC_WIDTH	= 0x04,
> +	DCON_REG_VRES		= 0x05,
> +	DCON_REG_VTOTAL		= 0x06,
> +	DCON_REG_VSYNC_WIDTH	= 0x07,
> +	DCON_REG_TIMEOUT	= 0x08,
> +	DCON_REG_SCAN_INT	= 0x09,
> +	DCON_REG_BRIGHT		= 0x0a,
> +	DCON_REG_MEM_OPT_A	= 0x41,
> +	DCON_REG_MEM_OPT_B	= 0x42,
> +};
> +
> +/* DCON_REG_MODE */
> +enum {
> +	MODE_PASSTHRU		= BIT(0),
> +	MODE_SLEEP		= BIT(1),
> +	MODE_SLEEP_AUTO		= BIT(2),
> +	MODE_BL_ENABLE		= BIT(3),
> +	MODE_BLANK		= BIT(4),
> +	MODE_CSWIZZLE		= BIT(5),
> +	MODE_COL_AA		= BIT(6),
> +	MODE_MONO_LUMA		= BIT(7),
> +	MODE_SCAN_INT		= BIT(8),
> +	MODE_CLOCKDIV		= BIT(9),
> +	MODE_DEBUG		= BIT(14),
> +	MODE_SELFTEST		= BIT(15),
> +};
> +
> +struct hx8837_priv {
> +	struct regmap *regmap;
> +	struct gpio_desc *load_gpio;
> +
> +	struct drm_bridge *panel_bridge;
> +	struct drm_panel *panel;
No need for the panel pointer - use a local variable in the probe
function 

> +	struct drm_bridge bridge;
> +};
> +
> +static int hx8837_bridge_attach(struct drm_bridge *bridge,
> +				enum drm_bridge_attach_flags flags)
> +{
> +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> +
> +	return drm_bridge_attach(bridge->encoder, priv->panel_bridge,
> +				 bridge, flags);
> +}
> +
> +static enum drm_mode_status hx8837_bridge_mode_valid(
> +				struct drm_bridge *bridge,
> +				const struct drm_display_info *info,
> +				const struct drm_display_mode *mode)
> +{
> +	if (mode->hdisplay > 0xffff)
> +		return MODE_BAD_HVALUE;
> +	if (mode->htotal > 0xffff)
> +		return MODE_BAD_HVALUE;
> +	if (mode->hsync_start - mode->hdisplay > 0xff)
> +		return MODE_HBLANK_WIDE;
> +	if (mode->hsync_end - mode->hsync_start > 0xff)
> +		return MODE_HSYNC_WIDE;
> +	if (mode->vdisplay > 0xffff)
> +		return MODE_BAD_VVALUE;
> +	if (mode->vtotal > 0xffff)
> +		return MODE_BAD_VVALUE;
> +	if (mode->vsync_start - mode->vdisplay > 0xff)
> +		return MODE_VBLANK_WIDE;
> +	if (mode->vsync_end - mode->vsync_start > 0xff)
> +		return MODE_VSYNC_WIDE;
> +
> +	return MODE_OK;
> +}
> +
> +static void hx8837_bridge_disable(struct drm_bridge *bridge)
> +{
> +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> +	int ret;
> +
> +	ret = gpiod_direction_output(priv->load_gpio, 0);
> +	if (ret)
> +		DRM_ERROR("error enabling the dcon load: %d\n", ret);
The driver uses both dev_xxx() and DRM_XXX for logging.
Please stick to one way to do logging - I prefer for bridge drivers
the dev_* variants.

> +
> +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> +					       MODE_PASSTHRU |
> +					       MODE_SLEEP,
> +					       MODE_PASSTHRU |
> +					       MODE_SLEEP);
> +	if (ret)
> +		DRM_ERROR("error disabling the dcon: %d\n", ret);
> +}
> +
> +static void hx8837_bridge_enable(struct drm_bridge *bridge)
> +{
> +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> +	int ret;
> +
> +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> +					       MODE_PASSTHRU |
> +					       MODE_SLEEP |
> +					       MODE_SLEEP_AUTO |
> +					       MODE_BLANK |
> +					       MODE_SCAN_INT |
> +					       MODE_CLOCKDIV |
> +					       MODE_DEBUG |
> +					       MODE_SELFTEST,
> +					       MODE_PASSTHRU);
> +	if (ret)
> +		DRM_ERROR("error enabling the dcon: %d\n", ret);
> +
> +	ret = gpiod_direction_output(priv->load_gpio, 1);
> +	if (ret)
> +		DRM_ERROR("error enabling the dcon load: %d\n", ret);
> +}
> +
> +static void hx8837_bridge_mode_set(struct drm_bridge *bridge,
> +			   const struct drm_display_mode *mode,
> +			   const struct drm_display_mode *adjusted_mode)
> +{
> +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> +
> +	regmap_write(priv->regmap, DCON_REG_HRES, mode->hdisplay);
> +	regmap_write(priv->regmap, DCON_REG_HTOTAL, mode->htotal);
> +	regmap_write(priv->regmap, DCON_REG_HSYNC_WIDTH,
> +			(mode->hsync_start - mode->hdisplay) << 8 |
> +			(mode->hsync_end - mode->hsync_start));
> +	regmap_write(priv->regmap, DCON_REG_VRES, mode->vdisplay);
> +	regmap_write(priv->regmap, DCON_REG_VTOTAL, mode->vtotal);
> +	regmap_write(priv->regmap, DCON_REG_VSYNC_WIDTH,
> +			(mode->vsync_start - mode->vdisplay) << 8 |
> +			(mode->vsync_end - mode->vsync_start));
> +}
> +
> +static const struct drm_bridge_funcs hx8837_bridge_funcs = {
> +	.attach = hx8837_bridge_attach,
> +	.mode_valid = hx8837_bridge_mode_valid,
> +	.disable = hx8837_bridge_disable,
> +	.enable = hx8837_bridge_enable,
> +	.mode_set = hx8837_bridge_mode_set,
> +};
> +
> +static int hx8837_bl_update_status(struct backlight_device *bl)
> +{
> +	struct hx8837_priv *priv = bl_get_data(bl);
> +	unsigned int val;
> +	int ret;
> +
> +	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
> +					       0x000f,
> +					       bl->props.brightness);

Use backlight_get_brightness() to get the brightness.
This will also make sure 0 is returned when backlight is off so the
logic a few lines down is correct.

> +	if (ret) {
> +		dev_err(&bl->dev, "error setting the backlight: %d\n", ret);
> +		return ret;
> +	}
> +
> +	if (bl->props.brightness)
> +		val = MODE_CSWIZZLE | MODE_COL_AA;
> +	else
> +		val = MODE_MONO_LUMA;
> +
> +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> +					       MODE_CSWIZZLE |
> +					       MODE_COL_AA |
> +					       MODE_MONO_LUMA,
> +					       val);
> +	if (ret) {
> +		dev_err(&bl->dev, "error setting color mode: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct backlight_ops hx8837_bl_ops = {
> +	.update_status = hx8837_bl_update_status,
> +};
> +
> +static const struct regmap_config hx8837_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +	.max_register = 0x4c,
> +	.val_format_endian = REGMAP_ENDIAN_LITTLE,
> +};
> +
> +static int hx8837_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct backlight_properties bl_props = {
> +		.type = BACKLIGHT_RAW,
> +		.max_brightness = 0xf,
> +	};
Make it const
Maybe use a constant for the max value as it is also used as a mask
later.

> +	struct device *dev = &client->dev;
> +	struct backlight_device *bl;
> +	struct hx8837_priv *priv;
> +	unsigned int val;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, priv);
> +
> +	priv->load_gpio = devm_gpiod_get(dev, "load", GPIOD_ASIS);
> +	if (IS_ERR(priv->load_gpio))
> +		return PTR_ERR(priv->load_gpio);
> +
> +	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1,
> +					  &priv->panel, NULL);
> +	if (ret)
> +		return ret;
> +
> +	if (priv->panel->backlight) {
> +		dev_err(dev, "the panel already has a backlight controller\n");
> +		return -ENODEV;
> +	}
> +
> +	priv->panel_bridge = devm_drm_panel_bridge_add(dev, priv->panel);
> +	if (IS_ERR(priv->panel_bridge))
> +		return PTR_ERR(priv->panel_bridge);
> +
> +	priv->regmap = devm_regmap_init_i2c(client, &hx8837_regmap_config);
> +	if (IS_ERR(priv->regmap)) {
> +		dev_err(dev, "regmap init failed\n");
> +		return PTR_ERR(priv->regmap);
> +	}
> +
> +	ret = regmap_read(priv->regmap, DCON_REG_ID, &val);
> +	if (ret < 0) {
> +		dev_err(dev, "error reading the model id: %d\n", ret);
> +		return ret;
> +	}
> +	if ((val & 0xff00) != 0xdc00) {
> +		dev_err(dev, "the device is not a hx8837\n");
> +		return -ENODEV;
> +	}
> +
> +	ret = regmap_read(priv->regmap, DCON_REG_BRIGHT, &val);
> +	if (ret < 0) {
> +		dev_err(&bl->dev, "error getting the backlight: %d\n", ret);
> +		return ret;
> +	}
> +	bl_props.brightness = val & 0xf;
> +
> +	bl = devm_backlight_device_register(dev, dev_name(dev), dev, priv,
> +					    &hx8837_bl_ops, &bl_props);
> +	if (IS_ERR(bl)) {
> +		dev_err(dev, "failed to register backlight\n");
> +		return PTR_ERR(bl);
> +	}
> +
> +	priv->panel->backlight = bl;
> +
> +	INIT_LIST_HEAD(&priv->bridge.list);
> +	priv->bridge.funcs = &hx8837_bridge_funcs;
> +	priv->bridge.of_node = dev->of_node;
> +	drm_bridge_add(&priv->bridge);
> +
> +	dev_info(dev, "HiMax HX8837 Display Controller Driver\n");
> +	return 0;
> +}
> +
> +static int hx8837_remove(struct i2c_client *client)
> +{
> +	struct device *dev = &client->dev;
> +	struct hx8837_priv *priv = dev_get_drvdata(dev);
> +
> +	drm_bridge_remove(&priv->bridge);

> +	priv->panel->backlight = NULL;
I cannot see why this is needed.
IF this is needed we have a bug in the core stuff we need to fix.

> +
> +	return 0;
> +}
> +
> +static const struct of_device_id hx8837_dt_ids[] = {
> +	{ .compatible = "himax,hx8837", },
> +	{ }
We often see { /* sentinel */ },
in these cases.

> +};
> +MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
> +
> +static const struct i2c_device_id hx8837_ids[] = {
> +	{ "hx8837", 0 },
> +	{ }
Likewise

> +};
> +MODULE_DEVICE_TABLE(i2c, hx8837_ids);
> +
> +static struct i2c_driver hx8837_driver = {
> +	.probe = hx8837_probe,
> +	.remove = hx8837_remove,
> +	.driver = {
> +		.name = "hx8837",
> +		.of_match_table = of_match_ptr(hx8837_dt_ids),
> +	},
> +	.id_table = hx8837_ids,
> +};
> +
> +module_i2c_driver(hx8837_driver);
> +
> +MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
> +MODULE_DESCRIPTION("HiMax HX8837 Display Controller Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.26.2
> 
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Re: [RESEND PATCH v5 2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

[Lubomir Rintel]

Hello Sam,

On Fri, Oct 16, 2020 at 10:07:34PM +0200, Sam Ravnborg wrote:
> Hi Lubomir.
> 
> On Sat, Sep 26, 2020 at 02:07:19AM +0200, Lubomir Rintel wrote:
> > Himax HX8837 is used to drive the LCD panel on OLPC platforms.
> > 
> > It controls the panel backlight and is able to refresh it when the LCD
> > controller (and the rest of the plaform) is powered off.
> > 
> > It also converts regular RGB color data from the LCDC so that it looks
> > reasonable on the OLPC LCD panel with a monochromatic layer on top of a
> > layer that can either reflect light (b/w sunlight readable mode) or light
> > pattern of red, green and blue pixels.
> > 
> > At this point, the driver is rather basic. The self-refresh mode is not
> > supported. There's no way of independently controlling the color swizzling,
> > antialiasing or b/w conversion, but it probably isn't too useful either.
> > 
> > There's another driver for the same hardware on OLPC XO-1.5 and XO-1.75
> > in drivers/staging/olpc_dcon. The display on that hardware doesn't utilize
> > DRM, so this driver doesn't replace the other one yet.
> > 
> > Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
> 
> A little feedback follows.
> 
> 	Sam
> 
> > 
> > ---
> > Changes since v3:
> > - Added this patch, in place of a driver derived from
> >   drivers/staging/olpc_dcon. Compared to the previous one this
> >   implements the bare minimum, without the fancy stuff such as
> >   self-refresh that need more work/thinking.
> > 
> >  drivers/gpu/drm/bridge/Kconfig        |  13 ++
> >  drivers/gpu/drm/bridge/Makefile       |   1 +
> >  drivers/gpu/drm/bridge/himax-hx8837.c | 325 ++++++++++++++++++++++++++
> >  3 files changed, 339 insertions(+)
> >  create mode 100644 drivers/gpu/drm/bridge/himax-hx8837.c
> > 
> > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> > index ef91646441b16..6a923dd56c1d5 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -48,6 +48,19 @@ config DRM_DISPLAY_CONNECTOR
> >  	  on ARM-based platforms. Saying Y here when this driver is not needed
> >  	  will not cause any issue.
> >  
> > +config DRM_HIMAX_HX8837
> > +        tristate "HiMax HX8837 OLPC Display Controller"
> > +	depends on OF
> > +	depends on OLPC || ARCH_MMP || COMPILE_TEST
> > +	select DRM_KMS_HELPER
> > +        select BACKLIGHT_LCD_SUPPORT
> > +        select BACKLIGHT_CLASS_DEVICE
> > +        help
> > +          Enable support for HiMax HX8837 Display Controller as found in the
> > +          OLPC XO laptops.
> > +
> > +          If your laptop doesn't have green ears, say "N"
> 
> There is a mixture of tabs and spaces for indent - use tabs only (and
> tabs + 2 spaces for the help text).
> 
> 
> > +
> >  config DRM_LONTIUM_LT9611
> >  	tristate "Lontium LT9611 DSI/HDMI bridge"
> >  	select SND_SOC_HDMI_CODEC if SND_SOC
> > diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> > index 2b3aff104e466..21f72df3260db 100644
> > --- a/drivers/gpu/drm/bridge/Makefile
> > +++ b/drivers/gpu/drm/bridge/Makefile
> > @@ -2,6 +2,7 @@
> >  obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
> >  obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
> >  obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
> > +obj-$(CONFIG_DRM_HIMAX_HX8837) += himax-hx8837.o
> Please add in alphabetical order.
> 
> >  obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
> >  obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
> >  obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
> > diff --git a/drivers/gpu/drm/bridge/himax-hx8837.c b/drivers/gpu/drm/bridge/himax-hx8837.c
> > new file mode 100644
> > index 0000000000000..1e97fcb8ce505
> > --- /dev/null
> > +++ b/drivers/gpu/drm/bridge/himax-hx8837.c
> > @@ -0,0 +1,325 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * HiMax HX8837 Display Controller Driver
> > + *
> > + * Datasheet: http://wiki.laptop.org/images/0/09/DCON_datasheet_HX8837-A.pdf
> > + *
> > + * Copyright (C) 2020 Lubomir Rintel
> > + */
> > +
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/module.h>
> > +#include <linux/regmap.h>
> > +
> > +#include <drm/drm_atomic_helper.h>
> > +#include <drm/drm_panel.h>
> > +#include <drm/drm_bridge.h>
> > +#include <drm/drm_of.h>
> > +#include <drm/drm_print.h>
> > +#include <drm/drm_probe_helper.h>
> In blocks are good but please add them in alphabetical order.
> 
> > +
> > +#define bridge_to_hx8837_priv(x) \
> > +	container_of(x, struct hx8837_priv, bridge)
> > +
> > +/* DCON registers */
> > +enum {
> > +	DCON_REG_ID		= 0x00,
> > +	DCON_REG_MODE		= 0x01,
> > +	DCON_REG_HRES		= 0x02,
> > +	DCON_REG_HTOTAL		= 0x03,
> > +	DCON_REG_HSYNC_WIDTH	= 0x04,
> > +	DCON_REG_VRES		= 0x05,
> > +	DCON_REG_VTOTAL		= 0x06,
> > +	DCON_REG_VSYNC_WIDTH	= 0x07,
> > +	DCON_REG_TIMEOUT	= 0x08,
> > +	DCON_REG_SCAN_INT	= 0x09,
> > +	DCON_REG_BRIGHT		= 0x0a,
> > +	DCON_REG_MEM_OPT_A	= 0x41,
> > +	DCON_REG_MEM_OPT_B	= 0x42,
> > +};
> > +
> > +/* DCON_REG_MODE */
> > +enum {
> > +	MODE_PASSTHRU		= BIT(0),
> > +	MODE_SLEEP		= BIT(1),
> > +	MODE_SLEEP_AUTO		= BIT(2),
> > +	MODE_BL_ENABLE		= BIT(3),
> > +	MODE_BLANK		= BIT(4),
> > +	MODE_CSWIZZLE		= BIT(5),
> > +	MODE_COL_AA		= BIT(6),
> > +	MODE_MONO_LUMA		= BIT(7),
> > +	MODE_SCAN_INT		= BIT(8),
> > +	MODE_CLOCKDIV		= BIT(9),
> > +	MODE_DEBUG		= BIT(14),
> > +	MODE_SELFTEST		= BIT(15),
> > +};
> > +
> > +struct hx8837_priv {
> > +	struct regmap *regmap;
> > +	struct gpio_desc *load_gpio;
> > +
> > +	struct drm_bridge *panel_bridge;
> > +	struct drm_panel *panel;
> No need for the panel pointer - use a local variable in the probe
> function 
> 
> > +	struct drm_bridge bridge;
> > +};
> > +
> > +static int hx8837_bridge_attach(struct drm_bridge *bridge,
> > +				enum drm_bridge_attach_flags flags)
> > +{
> > +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> > +
> > +	return drm_bridge_attach(bridge->encoder, priv->panel_bridge,
> > +				 bridge, flags);
> > +}
> > +
> > +static enum drm_mode_status hx8837_bridge_mode_valid(
> > +				struct drm_bridge *bridge,
> > +				const struct drm_display_info *info,
> > +				const struct drm_display_mode *mode)
> > +{
> > +	if (mode->hdisplay > 0xffff)
> > +		return MODE_BAD_HVALUE;
> > +	if (mode->htotal > 0xffff)
> > +		return MODE_BAD_HVALUE;
> > +	if (mode->hsync_start - mode->hdisplay > 0xff)
> > +		return MODE_HBLANK_WIDE;
> > +	if (mode->hsync_end - mode->hsync_start > 0xff)
> > +		return MODE_HSYNC_WIDE;
> > +	if (mode->vdisplay > 0xffff)
> > +		return MODE_BAD_VVALUE;
> > +	if (mode->vtotal > 0xffff)
> > +		return MODE_BAD_VVALUE;
> > +	if (mode->vsync_start - mode->vdisplay > 0xff)
> > +		return MODE_VBLANK_WIDE;
> > +	if (mode->vsync_end - mode->vsync_start > 0xff)
> > +		return MODE_VSYNC_WIDE;
> > +
> > +	return MODE_OK;
> > +}
> > +
> > +static void hx8837_bridge_disable(struct drm_bridge *bridge)
> > +{
> > +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> > +	int ret;
> > +
> > +	ret = gpiod_direction_output(priv->load_gpio, 0);
> > +	if (ret)
> > +		DRM_ERROR("error enabling the dcon load: %d\n", ret);
> The driver uses both dev_xxx() and DRM_XXX for logging.
> Please stick to one way to do logging - I prefer for bridge drivers
> the dev_* variants.
> 
> > +
> > +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> > +					       MODE_PASSTHRU |
> > +					       MODE_SLEEP,
> > +					       MODE_PASSTHRU |
> > +					       MODE_SLEEP);
> > +	if (ret)
> > +		DRM_ERROR("error disabling the dcon: %d\n", ret);
> > +}
> > +
> > +static void hx8837_bridge_enable(struct drm_bridge *bridge)
> > +{
> > +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> > +	int ret;
> > +
> > +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> > +					       MODE_PASSTHRU |
> > +					       MODE_SLEEP |
> > +					       MODE_SLEEP_AUTO |
> > +					       MODE_BLANK |
> > +					       MODE_SCAN_INT |
> > +					       MODE_CLOCKDIV |
> > +					       MODE_DEBUG |
> > +					       MODE_SELFTEST,
> > +					       MODE_PASSTHRU);
> > +	if (ret)
> > +		DRM_ERROR("error enabling the dcon: %d\n", ret);
> > +
> > +	ret = gpiod_direction_output(priv->load_gpio, 1);
> > +	if (ret)
> > +		DRM_ERROR("error enabling the dcon load: %d\n", ret);
> > +}
> > +
> > +static void hx8837_bridge_mode_set(struct drm_bridge *bridge,
> > +			   const struct drm_display_mode *mode,
> > +			   const struct drm_display_mode *adjusted_mode)
> > +{
> > +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> > +
> > +	regmap_write(priv->regmap, DCON_REG_HRES, mode->hdisplay);
> > +	regmap_write(priv->regmap, DCON_REG_HTOTAL, mode->htotal);
> > +	regmap_write(priv->regmap, DCON_REG_HSYNC_WIDTH,
> > +			(mode->hsync_start - mode->hdisplay) << 8 |
> > +			(mode->hsync_end - mode->hsync_start));
> > +	regmap_write(priv->regmap, DCON_REG_VRES, mode->vdisplay);
> > +	regmap_write(priv->regmap, DCON_REG_VTOTAL, mode->vtotal);
> > +	regmap_write(priv->regmap, DCON_REG_VSYNC_WIDTH,
> > +			(mode->vsync_start - mode->vdisplay) << 8 |
> > +			(mode->vsync_end - mode->vsync_start));
> > +}
> > +
> > +static const struct drm_bridge_funcs hx8837_bridge_funcs = {
> > +	.attach = hx8837_bridge_attach,
> > +	.mode_valid = hx8837_bridge_mode_valid,
> > +	.disable = hx8837_bridge_disable,
> > +	.enable = hx8837_bridge_enable,
> > +	.mode_set = hx8837_bridge_mode_set,
> > +};
> > +
> > +static int hx8837_bl_update_status(struct backlight_device *bl)
> > +{
> > +	struct hx8837_priv *priv = bl_get_data(bl);
> > +	unsigned int val;
> > +	int ret;
> > +
> > +	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
> > +					       0x000f,
> > +					       bl->props.brightness);
> 
> Use backlight_get_brightness() to get the brightness.
> This will also make sure 0 is returned when backlight is off so the
> logic a few lines down is correct.

I'm not sure I understand this one. I'm wondering if you could help me out
with it before I follow up with v4.

Currently I read in the current brightness level in probe() (which
prevents struct backlight_properties, below, from being const) and the
nthe brightness is entirely in control of the driver via
update_status().

What would I need get_brightness() for? We know that whatever the driver
set is the current level. It doesn't seem to be called on backlight
device registration so it doesn't make the readin in probe()
unnecessary either.

> > +	if (ret) {
> > +		dev_err(&bl->dev, "error setting the backlight: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	if (bl->props.brightness)
> > +		val = MODE_CSWIZZLE | MODE_COL_AA;
> > +	else
> > +		val = MODE_MONO_LUMA;
> > +
> > +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> > +					       MODE_CSWIZZLE |
> > +					       MODE_COL_AA |
> > +					       MODE_MONO_LUMA,
> > +					       val);
> > +	if (ret) {
> > +		dev_err(&bl->dev, "error setting color mode: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct backlight_ops hx8837_bl_ops = {
> > +	.update_status = hx8837_bl_update_status,
> > +};
> > +
> > +static const struct regmap_config hx8837_regmap_config = {
> > +	.reg_bits = 8,
> > +	.val_bits = 16,
> > +	.max_register = 0x4c,
> > +	.val_format_endian = REGMAP_ENDIAN_LITTLE,
> > +};
> > +
> > +static int hx8837_probe(struct i2c_client *client,
> > +			const struct i2c_device_id *id)
> > +{
> > +	struct backlight_properties bl_props = {
> > +		.type = BACKLIGHT_RAW,
> > +		.max_brightness = 0xf,
> > +	};
> Make it const
> Maybe use a constant for the max value as it is also used as a mask
> later.
> 
> > +	struct device *dev = &client->dev;
> > +	struct backlight_device *bl;
> > +	struct hx8837_priv *priv;
> > +	unsigned int val;
> > +	int ret;
> > +
> > +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> > +	if (!priv)
> > +		return -ENOMEM;
> > +
> > +	dev_set_drvdata(dev, priv);
> > +
> > +	priv->load_gpio = devm_gpiod_get(dev, "load", GPIOD_ASIS);
> > +	if (IS_ERR(priv->load_gpio))
> > +		return PTR_ERR(priv->load_gpio);
> > +
> > +	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1,
> > +					  &priv->panel, NULL);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (priv->panel->backlight) {
> > +		dev_err(dev, "the panel already has a backlight controller\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	priv->panel_bridge = devm_drm_panel_bridge_add(dev, priv->panel);
> > +	if (IS_ERR(priv->panel_bridge))
> > +		return PTR_ERR(priv->panel_bridge);
> > +
> > +	priv->regmap = devm_regmap_init_i2c(client, &hx8837_regmap_config);
> > +	if (IS_ERR(priv->regmap)) {
> > +		dev_err(dev, "regmap init failed\n");
> > +		return PTR_ERR(priv->regmap);
> > +	}
> > +
> > +	ret = regmap_read(priv->regmap, DCON_REG_ID, &val);
> > +	if (ret < 0) {
> > +		dev_err(dev, "error reading the model id: %d\n", ret);
> > +		return ret;
> > +	}
> > +	if ((val & 0xff00) != 0xdc00) {
> > +		dev_err(dev, "the device is not a hx8837\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	ret = regmap_read(priv->regmap, DCON_REG_BRIGHT, &val);
> > +	if (ret < 0) {
> > +		dev_err(&bl->dev, "error getting the backlight: %d\n", ret);
> > +		return ret;
> > +	}
> > +	bl_props.brightness = val & 0xf;
> > +
> > +	bl = devm_backlight_device_register(dev, dev_name(dev), dev, priv,
> > +					    &hx8837_bl_ops, &bl_props);
> > +	if (IS_ERR(bl)) {
> > +		dev_err(dev, "failed to register backlight\n");
> > +		return PTR_ERR(bl);
> > +	}
> > +
> > +	priv->panel->backlight = bl;
> > +
> > +	INIT_LIST_HEAD(&priv->bridge.list);
> > +	priv->bridge.funcs = &hx8837_bridge_funcs;
> > +	priv->bridge.of_node = dev->of_node;
> > +	drm_bridge_add(&priv->bridge);
> > +
> > +	dev_info(dev, "HiMax HX8837 Display Controller Driver\n");
> > +	return 0;
> > +}
> > +
> > +static int hx8837_remove(struct i2c_client *client)
> > +{
> > +	struct device *dev = &client->dev;
> > +	struct hx8837_priv *priv = dev_get_drvdata(dev);
> > +
> > +	drm_bridge_remove(&priv->bridge);
> 
> > +	priv->panel->backlight = NULL;
> I cannot see why this is needed.
> IF this is needed we have a bug in the core stuff we need to fix.
> 
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id hx8837_dt_ids[] = {
> > +	{ .compatible = "himax,hx8837", },
> > +	{ }
> We often see { /* sentinel */ },
> in these cases.
> 
> > +};
> > +MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
> > +
> > +static const struct i2c_device_id hx8837_ids[] = {
> > +	{ "hx8837", 0 },
> > +	{ }
> Likewise
> 
> > +};
> > +MODULE_DEVICE_TABLE(i2c, hx8837_ids);
> > +
> > +static struct i2c_driver hx8837_driver = {
> > +	.probe = hx8837_probe,
> > +	.remove = hx8837_remove,
> > +	.driver = {
> > +		.name = "hx8837",
> > +		.of_match_table = of_match_ptr(hx8837_dt_ids),
> > +	},
> > +	.id_table = hx8837_ids,
> > +};
> > +
> > +module_i2c_driver(hx8837_driver);
> > +
> > +MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
> > +MODULE_DESCRIPTION("HiMax HX8837 Display Controller Driver");
> > +MODULE_LICENSE("GPL");

Thanks
Lubo

Re: [RESEND PATCH v5 2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

[Lubomir Rintel]

Hello Sam,

On Fri, Oct 16, 2020 at 10:07:34PM +0200, Sam Ravnborg wrote:
> Hi Lubomir.
> 
> On Sat, Sep 26, 2020 at 02:07:19AM +0200, Lubomir Rintel wrote:
> > Himax HX8837 is used to drive the LCD panel on OLPC platforms.
> > 
> > It controls the panel backlight and is able to refresh it when the LCD
> > controller (and the rest of the plaform) is powered off.
> > 
> > It also converts regular RGB color data from the LCDC so that it looks
> > reasonable on the OLPC LCD panel with a monochromatic layer on top of a
> > layer that can either reflect light (b/w sunlight readable mode) or light
> > pattern of red, green and blue pixels.
> > 
> > At this point, the driver is rather basic. The self-refresh mode is not
> > supported. There's no way of independently controlling the color swizzling,
> > antialiasing or b/w conversion, but it probably isn't too useful either.
> > 
> > There's another driver for the same hardware on OLPC XO-1.5 and XO-1.75
> > in drivers/staging/olpc_dcon. The display on that hardware doesn't utilize
> > DRM, so this driver doesn't replace the other one yet.
> > 
> > Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
> 
> A little feedback follows.
> 
> 	Sam
> 
> > 
> > ---
> > Changes since v3:
> > - Added this patch, in place of a driver derived from
> >   drivers/staging/olpc_dcon. Compared to the previous one this
> >   implements the bare minimum, without the fancy stuff such as
> >   self-refresh that need more work/thinking.
> > 
> >  drivers/gpu/drm/bridge/Kconfig        |  13 ++
> >  drivers/gpu/drm/bridge/Makefile       |   1 +
> >  drivers/gpu/drm/bridge/himax-hx8837.c | 325 ++++++++++++++++++++++++++
> >  3 files changed, 339 insertions(+)
> >  create mode 100644 drivers/gpu/drm/bridge/himax-hx8837.c
> > 
> > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> > index ef91646441b16..6a923dd56c1d5 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -48,6 +48,19 @@ config DRM_DISPLAY_CONNECTOR
> >  	  on ARM-based platforms. Saying Y here when this driver is not needed
> >  	  will not cause any issue.
> >  
> > +config DRM_HIMAX_HX8837
> > +        tristate "HiMax HX8837 OLPC Display Controller"
> > +	depends on OF
> > +	depends on OLPC || ARCH_MMP || COMPILE_TEST
> > +	select DRM_KMS_HELPER
> > +        select BACKLIGHT_LCD_SUPPORT
> > +        select BACKLIGHT_CLASS_DEVICE
> > +        help
> > +          Enable support for HiMax HX8837 Display Controller as found in the
> > +          OLPC XO laptops.
> > +
> > +          If your laptop doesn't have green ears, say "N"
> 
> There is a mixture of tabs and spaces for indent - use tabs only (and
> tabs + 2 spaces for the help text).
> 
> 
> > +
> >  config DRM_LONTIUM_LT9611
> >  	tristate "Lontium LT9611 DSI/HDMI bridge"
> >  	select SND_SOC_HDMI_CODEC if SND_SOC
> > diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> > index 2b3aff104e466..21f72df3260db 100644
> > --- a/drivers/gpu/drm/bridge/Makefile
> > +++ b/drivers/gpu/drm/bridge/Makefile
> > @@ -2,6 +2,7 @@
> >  obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
> >  obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
> >  obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
> > +obj-$(CONFIG_DRM_HIMAX_HX8837) += himax-hx8837.o
> Please add in alphabetical order.
> 
> >  obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
> >  obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
> >  obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
> > diff --git a/drivers/gpu/drm/bridge/himax-hx8837.c b/drivers/gpu/drm/bridge/himax-hx8837.c
> > new file mode 100644
> > index 0000000000000..1e97fcb8ce505
> > --- /dev/null
> > +++ b/drivers/gpu/drm/bridge/himax-hx8837.c
> > @@ -0,0 +1,325 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * HiMax HX8837 Display Controller Driver
> > + *
> > + * Datasheet: http://wiki.laptop.org/images/0/09/DCON_datasheet_HX8837-A.pdf
> > + *
> > + * Copyright (C) 2020 Lubomir Rintel
> > + */
> > +
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/module.h>
> > +#include <linux/regmap.h>
> > +
> > +#include <drm/drm_atomic_helper.h>
> > +#include <drm/drm_panel.h>
> > +#include <drm/drm_bridge.h>
> > +#include <drm/drm_of.h>
> > +#include <drm/drm_print.h>
> > +#include <drm/drm_probe_helper.h>
> In blocks are good but please add them in alphabetical order.
> 
> > +
> > +#define bridge_to_hx8837_priv(x) \
> > +	container_of(x, struct hx8837_priv, bridge)
> > +
> > +/* DCON registers */
> > +enum {
> > +	DCON_REG_ID		= 0x00,
> > +	DCON_REG_MODE		= 0x01,
> > +	DCON_REG_HRES		= 0x02,
> > +	DCON_REG_HTOTAL		= 0x03,
> > +	DCON_REG_HSYNC_WIDTH	= 0x04,
> > +	DCON_REG_VRES		= 0x05,
> > +	DCON_REG_VTOTAL		= 0x06,
> > +	DCON_REG_VSYNC_WIDTH	= 0x07,
> > +	DCON_REG_TIMEOUT	= 0x08,
> > +	DCON_REG_SCAN_INT	= 0x09,
> > +	DCON_REG_BRIGHT		= 0x0a,
> > +	DCON_REG_MEM_OPT_A	= 0x41,
> > +	DCON_REG_MEM_OPT_B	= 0x42,
> > +};
> > +
> > +/* DCON_REG_MODE */
> > +enum {
> > +	MODE_PASSTHRU		= BIT(0),
> > +	MODE_SLEEP		= BIT(1),
> > +	MODE_SLEEP_AUTO		= BIT(2),
> > +	MODE_BL_ENABLE		= BIT(3),
> > +	MODE_BLANK		= BIT(4),
> > +	MODE_CSWIZZLE		= BIT(5),
> > +	MODE_COL_AA		= BIT(6),
> > +	MODE_MONO_LUMA		= BIT(7),
> > +	MODE_SCAN_INT		= BIT(8),
> > +	MODE_CLOCKDIV		= BIT(9),
> > +	MODE_DEBUG		= BIT(14),
> > +	MODE_SELFTEST		= BIT(15),
> > +};
> > +
> > +struct hx8837_priv {
> > +	struct regmap *regmap;
> > +	struct gpio_desc *load_gpio;
> > +
> > +	struct drm_bridge *panel_bridge;
> > +	struct drm_panel *panel;
> No need for the panel pointer - use a local variable in the probe
> function 
> 
> > +	struct drm_bridge bridge;
> > +};
> > +
> > +static int hx8837_bridge_attach(struct drm_bridge *bridge,
> > +				enum drm_bridge_attach_flags flags)
> > +{
> > +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> > +
> > +	return drm_bridge_attach(bridge->encoder, priv->panel_bridge,
> > +				 bridge, flags);
> > +}
> > +
> > +static enum drm_mode_status hx8837_bridge_mode_valid(
> > +				struct drm_bridge *bridge,
> > +				const struct drm_display_info *info,
> > +				const struct drm_display_mode *mode)
> > +{
> > +	if (mode->hdisplay > 0xffff)
> > +		return MODE_BAD_HVALUE;
> > +	if (mode->htotal > 0xffff)
> > +		return MODE_BAD_HVALUE;
> > +	if (mode->hsync_start - mode->hdisplay > 0xff)
> > +		return MODE_HBLANK_WIDE;
> > +	if (mode->hsync_end - mode->hsync_start > 0xff)
> > +		return MODE_HSYNC_WIDE;
> > +	if (mode->vdisplay > 0xffff)
> > +		return MODE_BAD_VVALUE;
> > +	if (mode->vtotal > 0xffff)
> > +		return MODE_BAD_VVALUE;
> > +	if (mode->vsync_start - mode->vdisplay > 0xff)
> > +		return MODE_VBLANK_WIDE;
> > +	if (mode->vsync_end - mode->vsync_start > 0xff)
> > +		return MODE_VSYNC_WIDE;
> > +
> > +	return MODE_OK;
> > +}
> > +
> > +static void hx8837_bridge_disable(struct drm_bridge *bridge)
> > +{
> > +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> > +	int ret;
> > +
> > +	ret = gpiod_direction_output(priv->load_gpio, 0);
> > +	if (ret)
> > +		DRM_ERROR("error enabling the dcon load: %d\n", ret);
> The driver uses both dev_xxx() and DRM_XXX for logging.
> Please stick to one way to do logging - I prefer for bridge drivers
> the dev_* variants.
> 
> > +
> > +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> > +					       MODE_PASSTHRU |
> > +					       MODE_SLEEP,
> > +					       MODE_PASSTHRU |
> > +					       MODE_SLEEP);
> > +	if (ret)
> > +		DRM_ERROR("error disabling the dcon: %d\n", ret);
> > +}
> > +
> > +static void hx8837_bridge_enable(struct drm_bridge *bridge)
> > +{
> > +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> > +	int ret;
> > +
> > +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> > +					       MODE_PASSTHRU |
> > +					       MODE_SLEEP |
> > +					       MODE_SLEEP_AUTO |
> > +					       MODE_BLANK |
> > +					       MODE_SCAN_INT |
> > +					       MODE_CLOCKDIV |
> > +					       MODE_DEBUG |
> > +					       MODE_SELFTEST,
> > +					       MODE_PASSTHRU);
> > +	if (ret)
> > +		DRM_ERROR("error enabling the dcon: %d\n", ret);
> > +
> > +	ret = gpiod_direction_output(priv->load_gpio, 1);
> > +	if (ret)
> > +		DRM_ERROR("error enabling the dcon load: %d\n", ret);
> > +}
> > +
> > +static void hx8837_bridge_mode_set(struct drm_bridge *bridge,
> > +			   const struct drm_display_mode *mode,
> > +			   const struct drm_display_mode *adjusted_mode)
> > +{
> > +	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
> > +
> > +	regmap_write(priv->regmap, DCON_REG_HRES, mode->hdisplay);
> > +	regmap_write(priv->regmap, DCON_REG_HTOTAL, mode->htotal);
> > +	regmap_write(priv->regmap, DCON_REG_HSYNC_WIDTH,
> > +			(mode->hsync_start - mode->hdisplay) << 8 |
> > +			(mode->hsync_end - mode->hsync_start));
> > +	regmap_write(priv->regmap, DCON_REG_VRES, mode->vdisplay);
> > +	regmap_write(priv->regmap, DCON_REG_VTOTAL, mode->vtotal);
> > +	regmap_write(priv->regmap, DCON_REG_VSYNC_WIDTH,
> > +			(mode->vsync_start - mode->vdisplay) << 8 |
> > +			(mode->vsync_end - mode->vsync_start));
> > +}
> > +
> > +static const struct drm_bridge_funcs hx8837_bridge_funcs = {
> > +	.attach = hx8837_bridge_attach,
> > +	.mode_valid = hx8837_bridge_mode_valid,
> > +	.disable = hx8837_bridge_disable,
> > +	.enable = hx8837_bridge_enable,
> > +	.mode_set = hx8837_bridge_mode_set,
> > +};
> > +
> > +static int hx8837_bl_update_status(struct backlight_device *bl)
> > +{
> > +	struct hx8837_priv *priv = bl_get_data(bl);
> > +	unsigned int val;
> > +	int ret;
> > +
> > +	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
> > +					       0x000f,
> > +					       bl->props.brightness);
> 
> Use backlight_get_brightness() to get the brightness.
> This will also make sure 0 is returned when backlight is off so the
> logic a few lines down is correct.

I'm not sure I understand this one. I'm wondering if you could help me out
with it before I follow up with v4.

Currently I read in the current brightness level in probe() (which
prevents struct backlight_properties, below, from being const) and the
nthe brightness is entirely in control of the driver via
update_status().

What would I need get_brightness() for? We know that whatever the driver
set is the current level. It doesn't seem to be called on backlight
device registration so it doesn't make the readin in probe()
unnecessary either.

> > +	if (ret) {
> > +		dev_err(&bl->dev, "error setting the backlight: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	if (bl->props.brightness)
> > +		val = MODE_CSWIZZLE | MODE_COL_AA;
> > +	else
> > +		val = MODE_MONO_LUMA;
> > +
> > +	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
> > +					       MODE_CSWIZZLE |
> > +					       MODE_COL_AA |
> > +					       MODE_MONO_LUMA,
> > +					       val);
> > +	if (ret) {
> > +		dev_err(&bl->dev, "error setting color mode: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct backlight_ops hx8837_bl_ops = {
> > +	.update_status = hx8837_bl_update_status,
> > +};
> > +
> > +static const struct regmap_config hx8837_regmap_config = {
> > +	.reg_bits = 8,
> > +	.val_bits = 16,
> > +	.max_register = 0x4c,
> > +	.val_format_endian = REGMAP_ENDIAN_LITTLE,
> > +};
> > +
> > +static int hx8837_probe(struct i2c_client *client,
> > +			const struct i2c_device_id *id)
> > +{
> > +	struct backlight_properties bl_props = {
> > +		.type = BACKLIGHT_RAW,
> > +		.max_brightness = 0xf,
> > +	};
> Make it const
> Maybe use a constant for the max value as it is also used as a mask
> later.
> 
> > +	struct device *dev = &client->dev;
> > +	struct backlight_device *bl;
> > +	struct hx8837_priv *priv;
> > +	unsigned int val;
> > +	int ret;
> > +
> > +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> > +	if (!priv)
> > +		return -ENOMEM;
> > +
> > +	dev_set_drvdata(dev, priv);
> > +
> > +	priv->load_gpio = devm_gpiod_get(dev, "load", GPIOD_ASIS);
> > +	if (IS_ERR(priv->load_gpio))
> > +		return PTR_ERR(priv->load_gpio);
> > +
> > +	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1,
> > +					  &priv->panel, NULL);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (priv->panel->backlight) {
> > +		dev_err(dev, "the panel already has a backlight controller\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	priv->panel_bridge = devm_drm_panel_bridge_add(dev, priv->panel);
> > +	if (IS_ERR(priv->panel_bridge))
> > +		return PTR_ERR(priv->panel_bridge);
> > +
> > +	priv->regmap = devm_regmap_init_i2c(client, &hx8837_regmap_config);
> > +	if (IS_ERR(priv->regmap)) {
> > +		dev_err(dev, "regmap init failed\n");
> > +		return PTR_ERR(priv->regmap);
> > +	}
> > +
> > +	ret = regmap_read(priv->regmap, DCON_REG_ID, &val);
> > +	if (ret < 0) {
> > +		dev_err(dev, "error reading the model id: %d\n", ret);
> > +		return ret;
> > +	}
> > +	if ((val & 0xff00) != 0xdc00) {
> > +		dev_err(dev, "the device is not a hx8837\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	ret = regmap_read(priv->regmap, DCON_REG_BRIGHT, &val);
> > +	if (ret < 0) {
> > +		dev_err(&bl->dev, "error getting the backlight: %d\n", ret);
> > +		return ret;
> > +	}
> > +	bl_props.brightness = val & 0xf;
> > +
> > +	bl = devm_backlight_device_register(dev, dev_name(dev), dev, priv,
> > +					    &hx8837_bl_ops, &bl_props);
> > +	if (IS_ERR(bl)) {
> > +		dev_err(dev, "failed to register backlight\n");
> > +		return PTR_ERR(bl);
> > +	}
> > +
> > +	priv->panel->backlight = bl;
> > +
> > +	INIT_LIST_HEAD(&priv->bridge.list);
> > +	priv->bridge.funcs = &hx8837_bridge_funcs;
> > +	priv->bridge.of_node = dev->of_node;
> > +	drm_bridge_add(&priv->bridge);
> > +
> > +	dev_info(dev, "HiMax HX8837 Display Controller Driver\n");
> > +	return 0;
> > +}
> > +
> > +static int hx8837_remove(struct i2c_client *client)
> > +{
> > +	struct device *dev = &client->dev;
> > +	struct hx8837_priv *priv = dev_get_drvdata(dev);
> > +
> > +	drm_bridge_remove(&priv->bridge);
> 
> > +	priv->panel->backlight = NULL;
> I cannot see why this is needed.
> IF this is needed we have a bug in the core stuff we need to fix.
> 
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id hx8837_dt_ids[] = {
> > +	{ .compatible = "himax,hx8837", },
> > +	{ }
> We often see { /* sentinel */ },
> in these cases.
> 
> > +};
> > +MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
> > +
> > +static const struct i2c_device_id hx8837_ids[] = {
> > +	{ "hx8837", 0 },
> > +	{ }
> Likewise
> 
> > +};
> > +MODULE_DEVICE_TABLE(i2c, hx8837_ids);
> > +
> > +static struct i2c_driver hx8837_driver = {
> > +	.probe = hx8837_probe,
> > +	.remove = hx8837_remove,
> > +	.driver = {
> > +		.name = "hx8837",
> > +		.of_match_table = of_match_ptr(hx8837_dt_ids),
> > +	},
> > +	.id_table = hx8837_ids,
> > +};
> > +
> > +module_i2c_driver(hx8837_driver);
> > +
> > +MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
> > +MODULE_DESCRIPTION("HiMax HX8837 Display Controller Driver");
> > +MODULE_LICENSE("GPL");

Thanks
Lubo
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Re: [RESEND PATCH v5 2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

[Sam Ravnborg]

Hi Lubomir.

> > > +static int hx8837_bl_update_status(struct backlight_device *bl)
> > > +{
> > > +	struct hx8837_priv *priv = bl_get_data(bl);
> > > +	unsigned int val;
> > > +	int ret;
> > > +
> > > +	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
> > > +					       0x000f,
> > > +					       bl->props.brightness);
> > 
> > Use backlight_get_brightness() to get the brightness.
> > This will also make sure 0 is returned when backlight is off so the
> > logic a few lines down is correct.
> 
> I'm not sure I understand this one. I'm wondering if you could help me out
> with it before I follow up with v4.
> 
> Currently I read in the current brightness level in probe() (which
> prevents struct backlight_properties, below, from being const) and the
> nthe brightness is entirely in control of the driver via
> update_status().
> 
> What would I need get_brightness() for? We know that whatever the driver
> set is the current level. It doesn't seem to be called on backlight
> device registration so it doesn't make the readin in probe()
> unnecessary either.

The request here is to replace the direct access to backlight properties
"bl->props.brightness" with the helper backlight_get_brightness(bl).

	Sam

Re: [RESEND PATCH v5 2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

[Sam Ravnborg]

Hi Lubomir.

> > > +static int hx8837_bl_update_status(struct backlight_device *bl)
> > > +{
> > > +	struct hx8837_priv *priv = bl_get_data(bl);
> > > +	unsigned int val;
> > > +	int ret;
> > > +
> > > +	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
> > > +					       0x000f,
> > > +					       bl->props.brightness);
> > 
> > Use backlight_get_brightness() to get the brightness.
> > This will also make sure 0 is returned when backlight is off so the
> > logic a few lines down is correct.
> 
> I'm not sure I understand this one. I'm wondering if you could help me out
> with it before I follow up with v4.
> 
> Currently I read in the current brightness level in probe() (which
> prevents struct backlight_properties, below, from being const) and the
> nthe brightness is entirely in control of the driver via
> update_status().
> 
> What would I need get_brightness() for? We know that whatever the driver
> set is the current level. It doesn't seem to be called on backlight
> device registration so it doesn't make the readin in probe()
> unnecessary either.

The request here is to replace the direct access to backlight properties
"bl->props.brightness" with the helper backlight_get_brightness(bl).

	Sam
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