Add panel backlight control using DPCD registers on the DisplayPort aux channel.
Signed-off-by: Rajeev Nandan rajeevny@codeaurora.org --- 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_ */