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) <dani...@kernel.org>
Signed-off-by: Nick Chan <towinche...@gmail.com>
---
drivers/video/backlight/Kconfig | 11 +++
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/apple_dwi_bl.c | 123 +++++++++++++++++++++++++
3 files changed, 135 insertions(+)
create mode 100644 drivers/video/backlight/apple_dwi_bl.c
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 3614a5d29c71..cee113bba30f 100644
--- 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 8fc98f760a8a..156ff9461fb3 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-$(CONFIG_BACKLIGHT_APPLE_DWI) += apple_dwi_bl.o
obj-$(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
index 000000000000..93bd744972d6
--- /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 <towinche...@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 <towinche...@gmail.com>");
+MODULE_LICENSE("Dual MIT/GPL");
--
2.48.1
