[PATCH v2 2/3] backlight: dwi_bl: Add Apple DWI backlight driver

[Krzysztof Kozlowski]

On Sat, Dec 07, 2024 at 09:03:15PM +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.
> 
> Signed-off-by: Nick Chan <towinchenmi at gmail.com>
> ---
>  drivers/video/backlight/Kconfig  |  12 +++
>  drivers/video/backlight/Makefile |   1 +
>  drivers/video/backlight/dwi_bl.c | 124 +++++++++++++++++++++++++++++++
>  3 files changed, 137 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.

Mixed/messed indentation. Some spaces?

> +
> +	  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

Please do not introduce other sorting way - it is sorted by config name.
Which will also point you to apple_bl.o and need of explaining the
differences, e.g. why this cannot be one driver.


>  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..d4bfd74b3129
> --- /dev/null
> +++ b/drivers/video/backlight/dwi_bl.c
> @@ -0,0 +1,124 @@
> +// 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 at 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);

sizeof(*)

> +	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);

Use helper for these two, devm_platform_get_and_ioremap_resource() or
similar.

Best regards,
Krzysztof