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@xxxxxxxxx>
> ---
> 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@xxxxxxxxx>
> + */
> +
> +#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.
