Add backlight driver for the panels supporting backlight control
using DPCD registers on the DisplayPort aux channel.
Changes in v2:
- New (most of the code reused from drm_dp_aux_backlight.c of v1)
Signed-off-by: Rajeev Nandan <rajeevny@xxxxxxxxxxxxxx>
---
drivers/video/backlight/Kconfig | 7 +
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/dp_aux_backlight.c | 245 +++++++++++++++++++++++++++++
3 files changed, 253 insertions(+)
create mode 100644 drivers/video/backlight/dp_aux_backlight.c
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index d83c87b..82c88f0 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -456,6 +456,13 @@ config BACKLIGHT_LED
If you have a LCD backlight adjustable by LED class driver, say Y
to enable this driver.
+config BACKLIGHT_DP_AUX
+ tristate "DisplayPort aux backlight driver"
+ depends on DRM && DRM_KMS_HELPER
+ help
+ If you have a panel backlight controlled by DPCD registers
+ on the DisplayPort aux channel, say Y to enable this driver.
+
endif # BACKLIGHT_CLASS_DEVICE
endmenu
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 685f3f1..ba23c7c 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -57,3 +57,4 @@ obj-$(CONFIG_BACKLIGHT_WM831X) += wm831x_bl.o
obj-$(CONFIG_BACKLIGHT_ARCXCNN) += arcxcnn_bl.o
obj-$(CONFIG_BACKLIGHT_RAVE_SP) += rave-sp-backlight.o
obj-$(CONFIG_BACKLIGHT_LED) += led_bl.o
+obj-$(CONFIG_BACKLIGHT_DP_AUX) += dp_aux_backlight.o
diff --git a/drivers/video/backlight/dp_aux_backlight.c b/drivers/video/backlight/dp_aux_backlight.c
new file mode 100644
index 00000000..235fb42
--- /dev/null
+++ b/drivers/video/backlight/dp_aux_backlight.c
@@ -0,0 +1,245 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Backlight driver to control the brightness over DisplayPort aux channel.
+ */
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <drm/drm_dp_helper.h>
+
+#define DP_AUX_MAX_BRIGHTNESS 0xffff
+
+/**
+ * struct dp_aux_backlight - DisplayPort aux backlight data
+ * @dev: pointer to our device.
+ * @aux: the DisplayPort aux channel.
+ * @enable_gpio: the backlight enable gpio.
+ * @enabled: true if backlight is enabled else false.
+ */
+struct dp_aux_backlight {
+ struct device *dev;
+ struct drm_dp_aux *aux;
+ struct gpio_desc *enable_gpio;
+ bool enabled;
+};
+
+static struct drm_dp_aux *i2c_to_aux(struct i2c_adapter *i2c)
+{
+ return container_of(i2c, struct drm_dp_aux, ddc);
+}
+
+static int dp_aux_backlight_enable(struct dp_aux_backlight *aux_bl)
+{
+ u8 val = 0;
+ int ret;
+
+ if (aux_bl->enabled)
+ return 0;
+
+ /* Set backlight control mode */
+ ret = drm_dp_dpcd_readb(aux_bl->aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
+ &val);
+ if (ret < 0)
+ return ret;
+
+ val &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
+ val |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
+ ret = drm_dp_dpcd_writeb(aux_bl->aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
+ val);
+ if (ret < 0)
+ return ret;
+
+ /* Enable backlight */
+ ret = drm_dp_dpcd_readb(aux_bl->aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
+ &val);
+ if (ret < 0)
+ return ret;
+
+ val |= DP_EDP_BACKLIGHT_ENABLE;
+ ret = drm_dp_dpcd_writeb(aux_bl->aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
+ val);
+ if (ret < 0)
+ return ret;
+
+ if (aux_bl->enable_gpio)
+ gpiod_set_value(aux_bl->enable_gpio, 1);
+
+ aux_bl->enabled = true;
+
+ return 0;
+}
+
+static int dp_aux_backlight_disable(struct dp_aux_backlight *aux_bl)
+{
+ u8 val = 0;
+ int ret;
+
+ if (!aux_bl->enabled)
+ return 0;
+
+ if (aux_bl->enable_gpio)
+ gpiod_set_value(aux_bl->enable_gpio, 0);
+
+ ret = drm_dp_dpcd_readb(aux_bl->aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
+ &val);
+ if (ret < 0)
+ return ret;
+
+ val &= ~DP_EDP_BACKLIGHT_ENABLE;
+ ret = drm_dp_dpcd_writeb(aux_bl->aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
+ val);
+ if (ret < 0)
+ return ret;
+
+ aux_bl->enabled = false;
+
+ return 0;
+}
+
+static int dp_aux_backlight_update_status(struct backlight_device *bd)
+{
+ struct dp_aux_backlight *aux_bl = bl_get_data(bd);
+ u16 brightness = backlight_get_brightness(bd);
+ u8 val[2] = { 0x0 };
+ int ret = 0;
+
+ if (brightness > 0) {
+ val[0] = brightness >> 8;
+ val[1] = brightness & 0xff;
+ ret = drm_dp_dpcd_write(aux_bl->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
+ val, sizeof(val));
+ if (ret < 0)
+ return ret;
+
+ dp_aux_backlight_enable(aux_bl);
+ } else {
+ dp_aux_backlight_disable(aux_bl);
+ }
+
+ return 0;
+}
+
+static int dp_aux_backlight_get_brightness(struct backlight_device *bd)
+{
+ struct dp_aux_backlight *aux_bl = bl_get_data(bd);
+ u8 val[2] = { 0x0 };
+ int ret = 0;
+
+ if (backlight_is_blank(bd))
+ return 0;
+
+ ret = drm_dp_dpcd_read(aux_bl->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
+ &val, sizeof(val));
+ if (ret < 0)
+ return ret;
+
+ return (val[0] << 8 | val[1]);
+}
+
+static const struct backlight_ops aux_bl_ops = {
+ .update_status = dp_aux_backlight_update_status,
+ .get_brightness = dp_aux_backlight_get_brightness,
+};
+
+
+static int dp_aux_backlight_probe(struct platform_device *pdev)
+{
+ struct dp_aux_backlight *aux_bl;
+ struct backlight_device *bd;
+ struct backlight_properties bl_props = { 0 };
+ struct device_node *np;
+ struct i2c_adapter *ddc;
+ int ret = 0;
+ u32 val;
+
+ aux_bl = devm_kzalloc(&pdev->dev, sizeof(*aux_bl), GFP_KERNEL);
+ if (!aux_bl)
+ return -ENOMEM;
+
+ aux_bl->dev = &pdev->dev;
+
+ np = of_parse_phandle(pdev->dev.of_node, "ddc-i2c-bus", 0);
+ if (!np) {
+ dev_err(&pdev->dev, "failed to get aux ddc I2C bus\n");
+ return -ENODEV;
+ }
+
+ ddc = of_find_i2c_adapter_by_node(np);
+ of_node_put(np);
+ if (!ddc)
+ return -EPROBE_DEFER;
+
+ aux_bl->aux = i2c_to_aux(ddc);
+ dev_dbg(&pdev->dev, "using dp aux %s\n", aux_bl->aux->name);
+
+ aux_bl->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
+ GPIOD_OUT_LOW);
+ if (IS_ERR(aux_bl->enable_gpio)) {
+ ret = PTR_ERR(aux_bl->enable_gpio);
+ goto free_ddc;
+ }
+
+ val = DP_AUX_MAX_BRIGHTNESS;
+ of_property_read_u32(pdev->dev.of_node, "max-brightness", &val);
+ if (val > DP_AUX_MAX_BRIGHTNESS)
+ val = DP_AUX_MAX_BRIGHTNESS;
+
+ bl_props.max_brightness = val;
+ bl_props.brightness = val;
+ bl_props.type = BACKLIGHT_RAW;
+ bd = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
+ &pdev->dev, aux_bl,
+ &aux_bl_ops, &bl_props);
+ if (IS_ERR(bd)) {
+ ret = PTR_ERR(bd);
+ dev_err(&pdev->dev,
+ "failed to register backlight (%d)\n", ret);
+ goto free_ddc;
+ }
+
+ platform_set_drvdata(pdev, bd);
+
+ return 0;
+
+free_ddc:
+ if (ddc)
+ put_device(&ddc->dev);
+
+ return ret;
+}
+
+static int dp_aux_backlight_remove(struct platform_device *pdev)
+{
+ struct backlight_device *bd = platform_get_drvdata(pdev);
+ struct dp_aux_backlight *aux_bl = bl_get_data(bd);
+ struct i2c_adapter *ddc = &aux_bl->aux->ddc;
+
+ if (ddc)
+ put_device(&ddc->dev);
+
+ return 0;
+}
+
+static const struct of_device_id dp_aux_bl_of_match_table[] = {
+ { .compatible = "dp-aux-backlight"},
+ {},
+}
+MODULE_DEVICE_TABLE(of, dp_aux_bl_of_match_table);
+
+static struct platform_driver dp_aux_backlight_driver = {
+ .driver = {
+ .name = "dp-aux-backlight",
+ .of_match_table = dp_aux_bl_of_match_table,
+ },
+ .probe = dp_aux_backlight_probe,
+ .remove = dp_aux_backlight_remove,
+
+};
+module_platform_driver(dp_aux_backlight_driver);
+
+MODULE_DESCRIPTION("DisplayPort aux backlight driver");
+MODULE_LICENSE("GPL v2");
--
2.7.4
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