Add panel backlight control using DPCD registers on the DisplayPort aux
channel.
Signed-off-by: Rajeev Nandan <rajeevny@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/Kconfig | 8 ++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/drm_dp_aux_backlight.c | 191 +++++++++++++++++++++++++++++++++
include/drm/drm_dp_aux_backlight.h | 29 +++++
4 files changed, 229 insertions(+)
create mode 100644 drivers/gpu/drm/drm_dp_aux_backlight.c
create mode 100644 include/drm/drm_dp_aux_backlight.h
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 85b79a7f..01f8a48 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -177,6 +177,14 @@ config DRM_DP_CEC
Note: not all adapters support this feature, and even for those
that do support this they often do not hook up the CEC pin.
+config DRM_DP_AUX_BACKLIGHT
+ bool "Enable DisplayPort aux backlight control support"
+ depends on DRM
+ select DRM_KMS_HELPER
+ help
+ Choose this option if you want to use panel backlight control
+ using DPCD registers on the DisplayPort aux channel.
+
config DRM_TTM
tristate
depends on DRM && MMU
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 926adef..e41e40f 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -53,6 +53,7 @@ drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
drm_kms_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o
+drm_kms_helper-$(CONFIG_DRM_DP_AUX_BACKLIGHT) += drm_dp_aux_backlight.o
obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
obj-$(CONFIG_DRM_DEBUG_SELFTEST) += selftests/
diff --git a/drivers/gpu/drm/drm_dp_aux_backlight.c b/drivers/gpu/drm/drm_dp_aux_backlight.c
new file mode 100644
index 0000000..2fc4ffb
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_aux_backlight.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <drm/drm_dp_aux_backlight.h>
+#include <drm/drm_dp_helper.h>
+#include <drm/drm_print.h>
+
+static int drm_dp_aux_brightness_set(struct backlight_device *bd)
+{
+ struct drm_dp_aux_backlight *pdata = bl_get_data(bd);
+ u16 brightness = bd->props.brightness;
+ u8 val[2] = { 0x0 };
+ int ret = 0;
+
+ if (!pdata->enabled)
+ return 0;
+
+ if (bd->props.power != FB_BLANK_UNBLANK ||
+ bd->props.fb_blank != FB_BLANK_UNBLANK ||
+ bd->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
+ brightness = 0;
+
+ val[0] = brightness >> 8;
+ val[1] = brightness & 0xff;
+ ret = drm_dp_dpcd_write(pdata->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
+ val, sizeof(val));
+ if (ret < 0)
+ return ret;
+
+ return ret;
+}
+
+static int drm_dp_aux_brightness_get(struct backlight_device *bd)
+{
+ struct drm_dp_aux_backlight *pdata = bl_get_data(bd);
+ u8 val[2] = { 0x0 };
+ int ret = 0;
+
+ if (!pdata->enabled)
+ return 0;
+
+ if (bd->props.power != FB_BLANK_UNBLANK ||
+ bd->props.fb_blank != FB_BLANK_UNBLANK ||
+ bd->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
+ return 0;
+
+ ret = drm_dp_dpcd_read(pdata->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 = drm_dp_aux_brightness_set,
+ .get_brightness = drm_dp_aux_brightness_get,
+};
+
+/**
+ * drm_dp_aux_backlight_enable() - Enable DP aux backlight
+ * @aux_bl: the DP aux backlight to enable
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_aux_backlight_enable(struct drm_dp_aux_backlight *aux_bl)
+{
+ u8 val = 0;
+ int ret;
+
+ if (!aux_bl)
+ return -EINVAL;
+
+ 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;
+
+ ret = backlight_enable(aux_bl->bd);
+ if (ret < 0)
+ DRM_DEV_INFO(aux_bl->dev, "failed to enable backlight: %d\n",
+ ret);
+
+ aux_bl->enabled = true;
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_dp_aux_backlight_enable);
+
+/**
+ * drm_dp_aux_backlight_disable() - Disable DP aux backlight
+ * @aux_bl: the DP aux backlight to disable
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_aux_backlight_disable(struct drm_dp_aux_backlight *aux_bl)
+{
+ u8 val = 0;
+ int ret;
+
+ if (!aux_bl)
+ return -EINVAL;
+
+ if (!aux_bl->enabled)
+ return 0;
+
+ ret = backlight_disable(aux_bl->bd);
+ if (ret < 0)
+ DRM_DEV_INFO(aux_bl->dev, "failed to disable backlight: %d\n",
+ ret);
+
+ 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;
+}
+EXPORT_SYMBOL(drm_dp_aux_backlight_disable);
+
+/**
+ * drm_dp_aux_backlight_register() - register a DP aux backlight device
+ * @name: the name of the backlight device
+ * @aux_bl: the DP aux backlight to register
+ *
+ * Creates and registers a new backlight device that uses DPCD registers
+ * on the DisplayPort aux channel to control the brightness of the panel.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_aux_backlight_register(const char *name,
+ struct drm_dp_aux_backlight *aux_bl)
+{
+ struct backlight_properties bl_props = { 0 };
+ int max_brightness;
+ int ret = 0;
+
+ if (!name || !aux_bl || !aux_bl->aux)
+ return -EINVAL;
+
+ max_brightness = 0xffff;
+
+ bl_props.type = BACKLIGHT_RAW;
+ bl_props.brightness = max_brightness;
+ bl_props.max_brightness = max_brightness;
+ aux_bl->bd = devm_backlight_device_register(aux_bl->dev, name,
+ aux_bl->dev, aux_bl,
+ &aux_bl_ops, &bl_props);
+ if (IS_ERR(aux_bl->bd)) {
+ ret = PTR_ERR(aux_bl->bd);
+ DRM_DEV_ERROR(aux_bl->dev,
+ "failed to register backlight (%d)\n", ret);
+ aux_bl->bd = NULL;
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_dp_aux_backlight_register);
diff --git a/include/drm/drm_dp_aux_backlight.h b/include/drm/drm_dp_aux_backlight.h
new file mode 100644
index 0000000..23cc554
--- /dev/null
+++ b/include/drm/drm_dp_aux_backlight.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _DRM_DP_AUX_BACKLIGHT_H_
+#define _DRM_DP_AUX_BACKLIGHT_H_
+
+#include <linux/backlight.h>
+#include <drm/drm_dp_helper.h>
+
+/**
+ * struct drm_dp_aux_backlight - DisplayPort aux backlight
+ * @dev: the device to register
+ * @aux: the DisplayPort aux channel
+ * @bd: the backlight device
+ * @enabled: true if backlight is enabled else false.
+ */
+struct drm_dp_aux_backlight {
+ struct device *dev;
+ struct drm_dp_aux *aux;
+ struct backlight_device *bd;
+ bool enabled;
+};
+
+int drm_dp_aux_backlight_enable(struct drm_dp_aux_backlight *aux_bl);
+int drm_dp_aux_backlight_disable(struct drm_dp_aux_backlight *aux_bl);
+
+int drm_dp_aux_backlight_register(const char *name,
+ struct drm_dp_aux_backlight *aux_bl);
+
+#endif /* _DRM_DP_AUX_BACKLIGHT_H_ */
--
2.7.4
