diff mbox series

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

Message ID 20241211113512.19009-3-towinchenmi@gmail.com
State Superseded
Headers show
Series Apple DWI backlight driver | expand

Commit Message

Nick Chan Dec. 11, 2024, 11:34 a.m. UTC 
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

Comments

Daniel Thompson Jan. 8, 2025, 10:52 a.m. UTC | #1 
On Wed, Dec 11, 2024 at 07:34:38PM +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.
>
> 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 +++++++++++++++++++++++++++++++

I'd rather this was called apple_dwi_bl.c to match that config options,
etc.

> 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;

There should be something to indicate whether the backlight controls are
linear or logarithmic here.


> +static struct platform_driver dwi_bl_driver = {
> +	.driver		= {
> +		.name	= "dwi-bl",

Again, I'd rather see apple here too (although, to be clear, I'm
perfectly happy with all the static functions and variables being
prefixed only with dwi_bl).


Daniel.
Nick Chan Jan. 9, 2025, 3:52 p.m. UTC | #2 
Daniel Thompson 於 2025/1/8 下晝6:52 寫道:
> On Wed, Dec 11, 2024 at 07:34:38PM +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.
>>
>> 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 +++++++++++++++++++++++++++++++
> I'd rather this was called apple_dwi_bl.c to match that config options,
> etc.
Still trying to determine the type of the backlight control, I think it is linear however and I will send a new
version when I am more certain.


>
>> 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;
> There should be something to indicate whether the backlight controls are
> linear or logarithmic here.
>
>
>> +static struct platform_driver dwi_bl_driver = {
>> +	.driver		= {
>> +		.name	= "dwi-bl",
> Again, I'd rather see apple here too (although, to be clear, I'm
> perfectly happy with all the static functions and variables being
> prefixed only with dwi_bl).
Alright, I will rename the file and and the name of the driver to have apple, the functions
and variables will still not have apple though to not make the lines too long.


>
>
> Daniel.
Daniel Thompson Jan. 9, 2025, 5:15 p.m. UTC | #3 
On Thu, Jan 09, 2025 at 11:52:56PM +0800, Nick Chan wrote:
>
> Daniel Thompson 於 2025/1/8 下晝6:52 寫道:
> > On Wed, Dec 11, 2024 at 07:34:38PM +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.
> >>
> >> 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 +++++++++++++++++++++++++++++++
> > I'd rather this was called apple_dwi_bl.c to match that config options,
> > etc.
> Still trying to determine the type of the backlight control, I think
> it is linear however and I will send a new version when I am more
> certain.

If you've got an physicalinstance of the backlight then you can get a
general idea by comparing levels: 512, 1024, 1536 and 2047.

A linear backlight will feel make the gaps feel uneven (e.g. the
difference between 1536 and 2047 will look very different to the
difference difference between 512 and 1024). A logarithmic backligt
will make the perceived brightness intervals between the above all
feel pretty similar.


Daniel.
diff mbox series

Patch

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");