[PATCH v4 RESEND 0/3] Apple DWI backlight driver

[PATCH v4 RESEND 0/3] Apple DWI backlight driver

[Nick Chan]

Apple SoCs come with a 2-wire interface named DWI. On some iPhones, iPads
and iPod touches the backlight controller is connected via this interface.
This series adds a backlight driver for backlight controllers connected
this way.

Changes since v3:
- $ref to common.yaml in bindings
- (and then additionalProperties is changed to unevaluatedProperties)
- Use hex everywhere in bindings example
- Use sizeof(*dwi_bl) instead of the type of the struct when doing
devm_kzalloc()
- Use devm_platform_get_and_ioremap_resource() in driver
- Fix sorting in drivers/video/backlight/Makefile
- In drivers/video/backlight/Kconfig, move config to right after
BACKLIGHT_APPLE
- Explain this driver being completely different from apple_bl

v3: https://lore.kernel.org/asahi/20241209075908.140014-1-towinchenmi@gmail.com/T

Changes since v2:
- Add missing includes in driver
- Fix file path in MAINTAINERS

v2: https://lore.kernel.org/asahi/20241207130433.30351-1-towinchenmi@gmail.com/T

Changes since v1:
- Fixed dt-bindings $id.
- Make power-domains an optional property in dt-bindings.
- Added missing error checking after devm_ioremap_resource() in
dwi_bl_probe().

v1: https://lore.kernel.org/asahi/20241206172735.4310-1-towinchenmi@gmail.com/T

Nick Chan
---

Nick Chan (3):
  dt-bindings: leds: backlight: apple,dwi-bl: Add Apple DWI backlight
  backlight: dwi_bl: Add Apple DWI backlight driver
  MAINTAINERS: Add entries for Apple DWI backlight controller

 .../bindings/leds/backlight/apple,dwi-bl.yaml |  57 ++++++++
 MAINTAINERS                                   |   2 +
 drivers/video/backlight/Kconfig               |  12 ++
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/dwi_bl.c              | 122 ++++++++++++++++++
 5 files changed, 194 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
 create mode 100644 drivers/video/backlight/dwi_bl.c


base-commit: 4bbf9020becbfd8fc2c3da790855b7042fad455b
-- 
2.47.1

[PATCH v4 RESEND 1/3] dt-bindings: leds: backlight: apple,dwi-bl: Add Apple DWI backlight

[Nick Chan]

Add backlight controllers attached via Apple DWI 2-wire interface.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Nick Chan <towinchenmi@gmail.com>
---
 .../bindings/leds/backlight/apple,dwi-bl.yaml | 57 +++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml

diff --git a/Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml b/Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
new file mode 100644
index 000000000000..29caeb356e6f
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/apple,dwi-bl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple DWI 2-Wire Interface Backlight Controller
+
+maintainers:
+  - Nick Chan <towinchenmi@gmail.com>
+
+description:
+  Apple SoCs contain a 2-wire interface called DWI. On some Apple iPhones,
+  iPads and iPod touches with a LCD display, 1-2 backlight controllers
+  are connected via DWI. Interfacing with DWI controls all backlight
+  controllers at the same time. As such, the backlight controllers are
+  treated as a single controller regardless of the underlying
+  configuration.
+
+allOf:
+  - $ref: common.yaml#
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - apple,s5l8960x-dwi-bl
+          - apple,t7000-dwi-bl
+          - apple,s8000-dwi-bl
+          - apple,t8010-dwi-bl
+          - apple,t8015-dwi-bl
+      - const: apple,dwi-bl
+
+  reg:
+    maxItems: 1
+
+  power-domains:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    soc {
+      #address-cells = <2>;
+      #size-cells = <2>;
+
+      dwi_bl: backlight@20e200010 {
+        compatible = "apple,s5l8960x-dwi-bl", "apple,dwi-bl";
+        reg = <0x2 0x0e200010 0x0 0x8>;
+        power-domains = <&ps_dwi>;
+      };
+    };
-- 
2.47.1

[PATCH v4 RESEND 2/3] backlight: dwi_bl: Add Apple DWI backlight driver

[Nick Chan]

Add driver for backlight controllers attached via Apple DWI 2-wire
interface, which is found on some Apple iPhones, iPads and iPod touches
with a LCD display.

Although there is an existing apple_bl driver, it is for backlight
controllers on Intel Macs attached via PCI, which is completely different
from the Samsung-derived DWI block.

Signed-off-by: Nick Chan <towinchenmi@gmail.com>
---
 drivers/video/backlight/Kconfig  |  12 +++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/dwi_bl.c | 122 +++++++++++++++++++++++++++++++
 3 files changed, 135 insertions(+)
 create mode 100644 drivers/video/backlight/dwi_bl.c

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 3614a5d29c71..debb1326df63 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -290,6 +290,18 @@ config BACKLIGHT_APPLE
 	  If you have an Intel-based Apple say Y to enable a driver for its
 	  backlight.
 
+config BACKLIGHT_APPLE_DWI
+	tristate "Apple DWI 2-Wire Interface Backlight Driver"
+	depends on ARCH_APPLE || COMPILE_TEST
+	default y
+	help
+	  Say Y to enable the backlight driver for backlight controllers
+	  attached via the Apple DWI 2-wire interface which is found in some
+	  Apple iPhones, iPads and iPod touches.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called dwi_bl.
+
 config BACKLIGHT_QCOM_WLED
 	tristate "Qualcomm PMIC WLED Driver"
 	select REGMAP
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 8fc98f760a8a..45cc80d9ae22 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -23,6 +23,7 @@ obj-$(CONFIG_BACKLIGHT_ADP5520)		+= adp5520_bl.o
 obj-$(CONFIG_BACKLIGHT_ADP8860)		+= adp8860_bl.o
 obj-$(CONFIG_BACKLIGHT_ADP8870)		+= adp8870_bl.o
 obj-$(CONFIG_BACKLIGHT_APPLE)		+= apple_bl.o
+obj-$(CONFIG_BACKLIGHT_APPLE_DWI)	+= dwi_bl.o
 obj-$(CONFIG_BACKLIGHT_AS3711)		+= as3711_bl.o
 obj-$(CONFIG_BACKLIGHT_BD6107)		+= bd6107.o
 obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE)	+= backlight.o
diff --git a/drivers/video/backlight/dwi_bl.c b/drivers/video/backlight/dwi_bl.c
new file mode 100644
index 000000000000..59e5cad0fbd8
--- /dev/null
+++ b/drivers/video/backlight/dwi_bl.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Driver for backlight controllers attached via Apple DWI 2-wire interface
+ *
+ * Copyright (c) 2024 Nick Chan <towinchenmi@gmail.com>
+ */
+
+#include <linux/backlight.h>
+#include <linux/bitfield.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#define DWI_BL_CTL			0x0
+#define DWI_BL_CTL_SEND1		BIT(0)
+#define DWI_BL_CTL_SEND2		BIT(4)
+#define DWI_BL_CTL_SEND3		BIT(5)
+#define DWI_BL_CTL_LE_DATA		BIT(6)
+/* Only used on Apple A9 and later */
+#define DWI_BL_CTL_SEND4		BIT(12)
+
+#define DWI_BL_CMD			0x4
+#define DWI_BL_CMD_TYPE			GENMASK(31, 28)
+#define DWI_BL_CMD_TYPE_SET_BRIGHTNESS	0xa
+#define DWI_BL_CMD_DATA			GENMASK(10, 0)
+
+#define DWI_BL_CTL_SEND			(DWI_BL_CTL_SEND1 | \
+					 DWI_BL_CTL_SEND2 | \
+					 DWI_BL_CTL_SEND3 | \
+					 DWI_BL_CTL_LE_DATA | \
+					 DWI_BL_CTL_SEND4)
+
+#define DWI_BL_MAX_BRIGHTNESS		2047
+
+struct apple_dwi_bl {
+	void __iomem *base;
+};
+
+static int dwi_bl_update_status(struct backlight_device *bl)
+{
+	struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
+
+	int brightness = backlight_get_brightness(bl);
+
+	u32 cmd = 0;
+
+	cmd |= FIELD_PREP(DWI_BL_CMD_DATA, brightness);
+	cmd |= FIELD_PREP(DWI_BL_CMD_TYPE, DWI_BL_CMD_TYPE_SET_BRIGHTNESS);
+
+	writel(cmd, dwi_bl->base + DWI_BL_CMD);
+	writel(DWI_BL_CTL_SEND, dwi_bl->base + DWI_BL_CTL);
+
+	return 0;
+}
+
+static int dwi_bl_get_brightness(struct backlight_device *bl)
+{
+	struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
+
+	u32 cmd = readl(dwi_bl->base + DWI_BL_CMD);
+
+	return FIELD_GET(DWI_BL_CMD_DATA, cmd);
+}
+
+static const struct backlight_ops dwi_bl_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.get_brightness = dwi_bl_get_brightness,
+	.update_status	= dwi_bl_update_status
+};
+
+static int dwi_bl_probe(struct platform_device *dev)
+{
+	struct apple_dwi_bl *dwi_bl;
+	struct backlight_device *bl;
+	struct backlight_properties props;
+	struct resource *res;
+
+	dwi_bl = devm_kzalloc(&dev->dev, sizeof(*dwi_bl), GFP_KERNEL);
+	if (!dwi_bl)
+		return -ENOMEM;
+
+	dwi_bl->base = devm_platform_get_and_ioremap_resource(dev, 0, &res);
+	if (IS_ERR(dwi_bl->base))
+		return PTR_ERR(dwi_bl->base);
+
+	memset(&props, 0, sizeof(struct backlight_properties));
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = DWI_BL_MAX_BRIGHTNESS;
+
+	bl = devm_backlight_device_register(&dev->dev, dev->name, &dev->dev,
+					dwi_bl, &dwi_bl_ops, &props);
+	if (IS_ERR(bl))
+		return PTR_ERR(bl);
+
+	platform_set_drvdata(dev, dwi_bl);
+
+	bl->props.brightness = dwi_bl_get_brightness(bl);
+
+	return 0;
+}
+
+static const struct of_device_id dwi_bl_of_match[] = {
+	{ .compatible = "apple,dwi-bl" },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, dwi_bl_of_match);
+
+static struct platform_driver dwi_bl_driver = {
+	.driver		= {
+		.name	= "dwi-bl",
+		.of_match_table = dwi_bl_of_match
+	},
+	.probe		= dwi_bl_probe,
+};
+
+module_platform_driver(dwi_bl_driver);
+
+MODULE_DESCRIPTION("Apple DWI Backlight Driver");
+MODULE_AUTHOR("Nick Chan <towinchenmi@gmail.com>");
+MODULE_LICENSE("Dual MIT/GPL");
-- 
2.47.1

[PATCH v4 RESEND 3/3] MAINTAINERS: Add entries for Apple DWI backlight controller

[Nick Chan]

Add MAINTAINERS entries for the driver.

Signed-off-by: Nick Chan <towinchenmi@gmail.com>
---
 MAINTAINERS | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 910305c11e8a..54a6c8ca7017 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2196,6 +2196,7 @@ F:	Documentation/devicetree/bindings/i2c/apple,i2c.yaml
 F:	Documentation/devicetree/bindings/interrupt-controller/apple,*
 F:	Documentation/devicetree/bindings/iommu/apple,dart.yaml
 F:	Documentation/devicetree/bindings/iommu/apple,sart.yaml
+F:	Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
 F:	Documentation/devicetree/bindings/mailbox/apple,mailbox.yaml
 F:	Documentation/devicetree/bindings/net/bluetooth/brcm,bcm4377-bluetooth.yaml
 F:	Documentation/devicetree/bindings/nvme/apple,nvme-ans.yaml
@@ -2221,6 +2222,7 @@ F:	drivers/nvmem/apple-efuses.c
 F:	drivers/pinctrl/pinctrl-apple-gpio.c
 F:	drivers/pwm/pwm-apple.c
 F:	drivers/soc/apple/*
+F:	drivers/video/backlight/dwi_bl.c
 F:	drivers/watchdog/apple_wdt.c
 F:	include/dt-bindings/interrupt-controller/apple-aic.h
 F:	include/dt-bindings/pinctrl/apple.h
-- 
2.47.1