[PATCH 0/3] Apple DWI backlight driver

[PATCH 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 1-2 backlight controllers are attached via this interface.
Though, to software using this interface, there is effectively only one
controller to worry about since the registers changes the brightness
setting on all controllers at the same time. This series adds a backlight
driver for backlight controllers connected this way.

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 |  55 ++++++++
 MAINTAINERS                                   |   2 +
 drivers/video/backlight/Kconfig               |  12 ++
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/dwi_bl.c              | 123 ++++++++++++++++++
 5 files changed, 193 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
 create mode 100644 drivers/video/backlight/dwi_bl.c


base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37
-- 
2.47.1

[PATCH 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 | 55 +++++++++++++++++++
 1 file changed, 55 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..fa3789b0b043
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/apple,dwi.yaml#
+$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
+  - power-domains
+
+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

[PATCH 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 | 123 +++++++++++++++++++++++++++++++
 3 files changed, 136 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..6dd7edf661fd
--- /dev/null
+++ b/drivers/video/backlight/dwi_bl.c
@@ -0,0 +1,123 @@
+// 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/module.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/backlight.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);
+
+	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 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 1e930c7a58b1..36de76bc6fd4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2204,6 +2204,7 @@ F:	Documentation/devicetree/bindings/pci/apple,pcie.yaml
 F:	Documentation/devicetree/bindings/pinctrl/apple,pinctrl.yaml
 F:	Documentation/devicetree/bindings/power/apple*
 F:	Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml
+F:	Documentation/devicetree/bindings/video/backlight/apple,dwi-bl.yaml
 F:	Documentation/devicetree/bindings/watchdog/apple,wdt.yaml
 F:	arch/arm64/boot/dts/apple/
 F:	drivers/bluetooth/hci_bcm4377.c
@@ -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

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

[Rob Herring (Arm)]

On Sat, 07 Dec 2024 01:24:33 +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 | 55 +++++++++++++++++++
>  1 file changed, 55 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
> 

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:

dtschema/dtc warnings/errors:
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml: $id: Cannot determine base path from $id, relative path/filename doesn't match actual path or filename
 	 $id: http://devicetree.org/schemas/leds/backlight/apple,dwi.yaml
 	file: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20241206172735.4310-2-towinchenmi@gmail.com

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.

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

[kernel test robot]

Hi Nick,

kernel test robot noticed the following build errors:

[auto build test ERROR on 40384c840ea1944d7c5a392e8975ed088ecf0b37]

url:    https://github.com/intel-lab-lkp/linux/commits/Nick-Chan/dt-bindings-leds-backlight-apple-dwi-bl-Add-bindings-for-Apple-DWI-backlight/20241207-013254
base:   40384c840ea1944d7c5a392e8975ed088ecf0b37
patch link:    https://lore.kernel.org/r/20241206172735.4310-3-towinchenmi%40gmail.com
patch subject: [PATCH 2/3] backlight: dwi_bl: Add Apple DWI backlight driver
config: arc-randconfig-001-20241207 (https://download.01.org/0day-ci/archive/20241207/202412070721.9tZI9Ogl-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241207/202412070721.9tZI9Ogl-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412070721.9tZI9Ogl-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/video/backlight/dwi_bl.c: In function 'dwi_bl_update_status':
>> drivers/video/backlight/dwi_bl.c:46:16: error: implicit declaration of function 'FIELD_PREP' [-Werror=implicit-function-declaration]
      46 |         cmd |= FIELD_PREP(DWI_BL_CMD_DATA, brightness);
         |                ^~~~~~~~~~
   drivers/video/backlight/dwi_bl.c: In function 'dwi_bl_get_brightness':
>> drivers/video/backlight/dwi_bl.c:61:16: error: implicit declaration of function 'FIELD_GET' [-Werror=implicit-function-declaration]
      61 |         return FIELD_GET(DWI_BL_CMD_DATA, cmd);
         |                ^~~~~~~~~
   cc1: some warnings being treated as errors


vim +/FIELD_PREP +46 drivers/video/backlight/dwi_bl.c

    37	
    38	static int dwi_bl_update_status(struct backlight_device *bl)
    39	{
    40		struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
    41	
    42		int brightness = backlight_get_brightness(bl);
    43	
    44		u32 cmd = 0;
    45	
  > 46		cmd |= FIELD_PREP(DWI_BL_CMD_DATA, brightness);
    47		cmd |= FIELD_PREP(DWI_BL_CMD_TYPE, DWI_BL_CMD_TYPE_SET_BRIGHTNESS);
    48	
    49		writel(cmd, dwi_bl->base + DWI_BL_CMD);
    50		writel(DWI_BL_CTL_SEND, dwi_bl->base + DWI_BL_CTL);
    51	
    52		return 0;
    53	}
    54	
    55	static int dwi_bl_get_brightness(struct backlight_device *bl)
    56	{
    57		struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
    58	
    59		u32 cmd = readl(dwi_bl->base + DWI_BL_CMD);
    60	
  > 61		return FIELD_GET(DWI_BL_CMD_DATA, cmd);
    62	}
    63	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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

[kernel test robot]

Hi Nick,

kernel test robot noticed the following build errors:

[auto build test ERROR on 40384c840ea1944d7c5a392e8975ed088ecf0b37]

url:    https://github.com/intel-lab-lkp/linux/commits/Nick-Chan/dt-bindings-leds-backlight-apple-dwi-bl-Add-bindings-for-Apple-DWI-backlight/20241207-013254
base:   40384c840ea1944d7c5a392e8975ed088ecf0b37
patch link:    https://lore.kernel.org/r/20241206172735.4310-3-towinchenmi%40gmail.com
patch subject: [PATCH 2/3] backlight: dwi_bl: Add Apple DWI backlight driver
config: hexagon-randconfig-001-20241207 (https://download.01.org/0day-ci/archive/20241207/202412070752.4Q1AOuGo-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241207/202412070752.4Q1AOuGo-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412070752.4Q1AOuGo-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/video/backlight/dwi_bl.c:46:9: error: implicit declaration of function 'FIELD_PREP' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
           cmd |= FIELD_PREP(DWI_BL_CMD_DATA, brightness);
                  ^
>> drivers/video/backlight/dwi_bl.c:61:9: error: implicit declaration of function 'FIELD_GET' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
           return FIELD_GET(DWI_BL_CMD_DATA, cmd);
                  ^
   2 errors generated.


vim +/FIELD_PREP +46 drivers/video/backlight/dwi_bl.c

    37	
    38	static int dwi_bl_update_status(struct backlight_device *bl)
    39	{
    40		struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
    41	
    42		int brightness = backlight_get_brightness(bl);
    43	
    44		u32 cmd = 0;
    45	
  > 46		cmd |= FIELD_PREP(DWI_BL_CMD_DATA, brightness);
    47		cmd |= FIELD_PREP(DWI_BL_CMD_TYPE, DWI_BL_CMD_TYPE_SET_BRIGHTNESS);
    48	
    49		writel(cmd, dwi_bl->base + DWI_BL_CMD);
    50		writel(DWI_BL_CTL_SEND, dwi_bl->base + DWI_BL_CTL);
    51	
    52		return 0;
    53	}
    54	
    55	static int dwi_bl_get_brightness(struct backlight_device *bl)
    56	{
    57		struct apple_dwi_bl *dwi_bl = bl_get_data(bl);
    58	
    59		u32 cmd = readl(dwi_bl->base + DWI_BL_CMD);
    60	
  > 61		return FIELD_GET(DWI_BL_CMD_DATA, cmd);
    62	}
    63	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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

[kernel test robot]

Hi Nick,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 40384c840ea1944d7c5a392e8975ed088ecf0b37]

url:    https://github.com/intel-lab-lkp/linux/commits/Nick-Chan/dt-bindings-leds-backlight-apple-dwi-bl-Add-bindings-for-Apple-DWI-backlight/20241207-013254
base:   40384c840ea1944d7c5a392e8975ed088ecf0b37
patch link:    https://lore.kernel.org/r/20241206172735.4310-4-towinchenmi%40gmail.com
patch subject: [PATCH 3/3] MAINTAINERS: Add entries for Apple DWI backlight controller
reproduce: (https://download.01.org/0day-ci/archive/20241207/202412070751.g7TFM5AI-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412070751.g7TFM5AI-lkp@intel.com/

All warnings (new ones prefixed by >>):

   Warning: Documentation/devicetree/bindings/regulator/siliconmitus,sm5703-regulator.yaml references a file that doesn't exist: Documentation/devicetree/bindings/mfd/siliconmitus,sm5703.yaml
   Warning: Documentation/hwmon/g762.rst references a file that doesn't exist: Documentation/devicetree/bindings/hwmon/g762.txt
   Warning: Documentation/hwmon/isl28022.rst references a file that doesn't exist: Documentation/devicetree/bindings/hwmon/isl,isl28022.yaml
   Warning: Documentation/translations/ja_JP/SubmittingPatches references a file that doesn't exist: linux-2.6.12-vanilla/Documentation/dontdiff
>> Warning: MAINTAINERS references a file that doesn't exist: Documentation/devicetree/bindings/video/backlight/apple,dwi-bl.yaml
   Warning: MAINTAINERS references a file that doesn't exist: Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
   Warning: lib/Kconfig.debug references a file that doesn't exist: Documentation/dev-tools/fault-injection/fault-injection.rst
   Using alabaster theme

-- 
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