backlight: apple_dwi_bl: Add Apple DWI backlight driver

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.

Reviewed-by: "Daniel Thompson (RISCstar)" <danielt@kernel.org>
Signed-off-by: Nick Chan <towinchenmi@gmail.com>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Link: https://lore.kernel.org/r/20250214040306.16312-3-towinchenmi@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 3614a5d29c716e2cc36df532739652ff363319f2..cee113bba30f8561a037b291019fbc0a2ca66dac 100644 (file)
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -290,6 +290,17 @@ 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
+       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 apple_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 8fc98f760a8ad45912376e51992946dbf74dffa7..156ff9461fb333d76c5219f7951fa72ec7d120e7 100644 (file)
--- 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-$(CONFIG_BACKLIGHT_APPLE_DWI)      += apple_dwi_bl.o
 obj-$(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/apple_dwi_bl.c b/drivers/video/backlight/apple_dwi_bl.c
new file mode 100644 (file)
index 0000000..93bd744
--- /dev/null
+++ b/drivers/video/backlight/apple_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/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_PLATFORM;
+       props.max_brightness = DWI_BL_MAX_BRIGHTNESS;
+       props.scale = BACKLIGHT_SCALE_LINEAR;
+
+       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   = "apple-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");