[PATCH v3 0/3] Apple DWI backlight driver

[PATCH v3 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 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 bindings for 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 |  54 ++++++++
 MAINTAINERS                                   |   2 +
 drivers/video/backlight/Kconfig               |  12 ++
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/dwi_bl.c              | 126 ++++++++++++++++++
 5 files changed, 195 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
 create mode 100644 drivers/video/backlight/dwi_bl.c


base-commit: fac04efc5c793dccbd07e2d59af9f90b7fc0dca4
-- 
2.47.1

[PATCH v3 1/3] dt-bindings: leds: backlight: apple,dwi-bl: Add bindings for Apple DWI backlight

[Nick Chan]

Add the device tree bindings for backlight controllers attached via Apple
DWI 2-wire interface.

Signed-off-by: Nick Chan <towinchenmi@gmail.com>
---
 .../bindings/leds/backlight/apple,dwi-bl.yaml | 54 +++++++++++++++++++
 1 file changed, 54 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..9d4aa243f679
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
@@ -0,0 +1,54 @@
+# 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.
+
+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
+
+additionalProperties: false
+
+examples:
+  - |
+    soc {
+      #address-cells = <2>;
+      #size-cells = <2>;
+
+      dwi_bl: backlight@20e200010 {
+        compatible = "apple,s5l8960x-dwi-bl", "apple,dwi-bl";
+        reg = <0x2 0x0e200010 0 8>;
+        power-domains = <&ps_dwi>;
+      };
+    };
-- 
2.47.1

Re: [PATCH v3 1/3] dt-bindings: leds: backlight: apple,dwi-bl: Add bindings for Apple DWI backlight

[Krzysztof Kozlowski]

On Mon, Dec 09, 2024 at 03:58:33PM +0800, Nick Chan wrote:
> Add the device tree bindings for backlight controllers attached via Apple
> DWI 2-wire interface.
> 
> Signed-off-by: Nick Chan <towinchenmi@gmail.com>
> ---
>  .../bindings/leds/backlight/apple,dwi-bl.yaml | 54 +++++++++++++++++++
>  1 file changed, 54 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
> 

<form letter>
This is a friendly reminder during the review process.

It seems my or other reviewer's previous comments were not fully
addressed. Maybe the feedback got lost between the quotes, maybe you
just forgot to apply it. Please go back to the previous discussion and
either implement all requested changes or keep discussing them.

Thank you.
</form letter>

Best regards,
Krzysztof

[PATCH v3 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.

Signed-off-by: Nick Chan <towinchenmi@gmail.com>
---
 drivers/video/backlight/Kconfig  |  12 +++
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/dwi_bl.c | 126 +++++++++++++++++++++++++++++++
 3 files changed, 139 insertions(+)
 create mode 100644 drivers/video/backlight/dwi_bl.c

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 3614a5d29c71..e64cc3d51ac5 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -166,6 +166,18 @@ config BACKLIGHT_EP93XX
 	  To compile this driver as a module, choose M here: the module will
 	  be called ep93xx_bl.
 
+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_IPAQ_MICRO
 	tristate "iPAQ microcontroller backlight driver"
 	depends on MFD_IPAQ_MICRO
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 8fc98f760a8a..0a569d7f0210 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_BACKLIGHT_BD6107)		+= bd6107.o
 obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE)	+= backlight.o
 obj-$(CONFIG_BACKLIGHT_DA903X)		+= da903x_bl.o
 obj-$(CONFIG_BACKLIGHT_DA9052)		+= da9052_bl.o
+obj-$(CONFIG_BACKLIGHT_APPLE_DWI)	+= dwi_bl.o
 obj-$(CONFIG_BACKLIGHT_EP93XX)		+= ep93xx_bl.o
 obj-$(CONFIG_BACKLIGHT_GPIO)		+= gpio_backlight.o
 obj-$(CONFIG_BACKLIGHT_HP680)		+= hp680_bl.o
diff --git a/drivers/video/backlight/dwi_bl.c b/drivers/video/backlight/dwi_bl.c
new file mode 100644
index 000000000000..501c36bed8f3
--- /dev/null
+++ b/drivers/video/backlight/dwi_bl.c
@@ -0,0 +1,126 @@
+// 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(struct apple_dwi_bl), GFP_KERNEL);
+	if (!dwi_bl)
+		return -ENOMEM;
+
+	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENXIO;
+
+	dwi_bl->base = devm_ioremap_resource(&dev->dev, 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

Re: [PATCH v3 2/3] backlight: dwi_bl: Add Apple DWI backlight driver

[Krzysztof Kozlowski]

On Mon, Dec 09, 2024 at 03:58:34PM +0800, Nick Chan wrote:
> 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.
> 

Nothing improved here.

> Signed-off-by: Nick Chan <towinchenmi@gmail.com>
> ---
>  drivers/video/backlight/Kconfig  |  12 +++
>  drivers/video/backlight/Makefile |   1 +
>  drivers/video/backlight/dwi_bl.c | 126 +++++++++++++++++++++++++++++++
>  3 files changed, 139 insertions(+)
>  create mode 100644 drivers/video/backlight/dwi_bl.c
> 
> diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
> index 3614a5d29c71..e64cc3d51ac5 100644
> --- a/drivers/video/backlight/Kconfig
> +++ b/drivers/video/backlight/Kconfig
> @@ -166,6 +166,18 @@ config BACKLIGHT_EP93XX
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called ep93xx_bl.
>  
> +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_IPAQ_MICRO
>  	tristate "iPAQ microcontroller backlight driver"
>  	depends on MFD_IPAQ_MICRO
> diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
> index 8fc98f760a8a..0a569d7f0210 100644
> --- a/drivers/video/backlight/Makefile
> +++ b/drivers/video/backlight/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_BACKLIGHT_BD6107)		+= bd6107.o
>  obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE)	+= backlight.o
>  obj-$(CONFIG_BACKLIGHT_DA903X)		+= da903x_bl.o
>  obj-$(CONFIG_BACKLIGHT_DA9052)		+= da9052_bl.o
> +obj-$(CONFIG_BACKLIGHT_APPLE_DWI)	+= dwi_bl.o

Nothing improved here.

Best regards,
Krzysztof

Re: [PATCH v3 2/3] backlight: dwi_bl: Add Apple DWI backlight driver

[Nick Chan]

Krzysztof Kozlowski 於 2024/12/10 下午4:32 寫道:

> Nothing improved here.


This is sent before you left any review, v4 will have improvements

Nick Chan

Re: [PATCH v3 2/3] backlight: dwi_bl: Add Apple DWI backlight driver

[Krzysztof Kozlowski]

On 10/12/2024 09:47, Nick Chan wrote:
> 
> 
> Krzysztof Kozlowski 於 2024/12/10 下午4:32 寫道:
> 
>> Nothing improved here.
> 
> 
> This is sent before you left any review, v4 will have improvements
> 
Ah, ok. Just popped in the patchwork.

In general rule is one patchset per 24h (some maintainers expect one per
48h), so reviewers will be able to respond.

Best regards,
Krzysztof

[PATCH v3 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 17daa9ee9384..3a7dec3f9a5a 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