Re: [PATCH 1/1] drm/i915: Add Backlight Control using DPCD for eDP connectors

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On 09/30/2015 07:36 AM, Yetunde Adebisi wrote:
> This patch adds support for eDP backlight control using DPCD registers to
> backlight hooks in intel_panel.
> 
> It checks for backlight control over AUX channel capability and sets up
> function pointers to get and set the backlight brightness level if
> supported.
> 
> Cc: Bob Paauwe <bob.j.paauwe@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Deepak M <m.deepak@intel.com>
> Signed-off-by: Yetunde Adebisi <yetundex.adebisi@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c    | 185 +++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_drv.h   |   3 +
>  drivers/gpu/drm/i915/intel_panel.c |   5 +-
>  include/drm/drm_dp_helper.h        |   6 ++
>  4 files changed, 198 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index fa1a524..fc4b896 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -6259,3 +6259,188 @@ void intel_dp_mst_resume(struct drm_device *dev)
>  		}
>  	}
>  }
> +
> +static uint8_t read_aux_backlight_mode_set_reg(struct intel_dp *intel_dp)
> +{
> +	uint8_t dpcd_buf = 0;
> +
> +	if (intel_dp_dpcd_read_wake(&intel_dp->aux,
> +			DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> +			&dpcd_buf, sizeof(dpcd_buf)) < 0)
> +		DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> +				DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> +
> +	return dpcd_buf;
> +}
> +
> +static bool get_aux_backlight_enable(struct drm_dp_aux *aux)
> +{
> +	uint8_t read_val = 0;
> +
> +	if (intel_dp_dpcd_read_wake(aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
> +			&read_val, sizeof(read_val)) < 0) {
> +		DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> +				DP_EDP_DISPLAY_CONTROL_REGISTER);
> +		}
> +	return read_val & DP_EDP_BACKLIGHT_ENABLE;
> +}
> +
> +static void set_aux_backlight_enable(struct intel_dp *intel_dp, bool enable)
> +{
> +	uint8_t reg_val = 0;
> +
> +	if (intel_dp_dpcd_read_wake(&intel_dp->aux,
> +				DP_EDP_DISPLAY_CONTROL_REGISTER,
> +				&reg_val, sizeof(reg_val)) < 0) {
> +		DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> +				DP_EDP_DISPLAY_CONTROL_REGISTER);
> +		return;
> +	}
> +	if (enable)
> +		reg_val |= DP_EDP_BACKLIGHT_ENABLE;
> +	else
> +		reg_val &= ~(DP_EDP_BACKLIGHT_ENABLE);
> +
> +	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
> +			reg_val) < 0) {
> +		DRM_DEBUG_KMS("Failed to %s aux backlight\n",
> +				enable ? "enable" : "disable");
> +	}
> +}
> +
> +/**
> + * Read the current backlight value from DPCD register(s) based
> + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> + */
> +static uint32_t intel_dp_aux_get_backlight(struct intel_connector *connector)
> +{
> +	struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
> +	uint16_t read_val = 0;
> +
> +	if (intel_dp_dpcd_read_wake(&intel_dp->aux,
> +			DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> +			&read_val, sizeof(read_val)) < 0) {
> +		DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> +				DP_EDP_BACKLIGHT_BRIGHTNESS_MSB);
> +		return 0;
> +	}
> +	if (intel_dp->aux_blc_use_lsb) {
> +		uint8_t val_lsb = 0;
> +
> +		if (intel_dp_dpcd_read_wake(&intel_dp->aux,
> +				DP_EDP_BACKLIGHT_BRIGHTNESS_LSB,
> +				&val_lsb, sizeof(val_lsb)) < 0) {
> +			DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
> +					DP_EDP_BACKLIGHT_BRIGHTNESS_LSB);
> +			return 0;
> +		}
> +		read_val = (read_val << 8 | val_lsb);
> +	}
> +
> +	return read_val;
> +}
> +
> +/**
> + * Sends the current backlight level over the aux channel, checking if its using
> + * 8-bit or 16 bit value (MSB and LSB)
> + */
> +static void
> +intel_dp_aux_set_backlight(struct intel_connector *connector, u32 level)
> +{
> +	struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
> +	uint8_t vals[2] = { 0x0 };
> +
> +	vals[0] = level;
> +	DRM_DEBUG_KMS("Level 0x%x\n", level);
> +
> +	/* Write the MSB and/or LSB */
> +	 if (intel_dp->aux_blc_use_lsb) {
> +		vals[0] = (level & 0xFF00) >> 8;
> +		vals[1] = (level & 0xFF);
> +		if (drm_dp_dpcd_writeb(&intel_dp->aux,
> +				DP_EDP_BACKLIGHT_BRIGHTNESS_LSB, vals[1]) < 0) {
> +			DRM_DEBUG_KMS("Failed to write aux backlight level\n");
> +			return;
> +		}
> +	 }
> +	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> +			vals[0]) < 0) {
> +		DRM_DEBUG_KMS("Failed to write aux backlight level\n");
> +		return;
> +	}
> +}
> +
> +static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
> +{
> +	set_aux_backlight_enable(intel_attached_dp(&connector->base), true);
> +}
> +
> +static void intel_dp_aux_disable_backlight(struct intel_connector *connector)
> +{
> +	set_aux_backlight_enable(intel_attached_dp(&connector->base), false);
> +}
> +
> +static int intel_dp_aux_setup_backlight(struct intel_connector *connector,
> +			       enum pipe pipe)
> +{
> +	struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
> +	struct intel_panel *panel = &connector->panel;
> +
> +	if (!intel_dp_aux_display_control_capable(connector)) {
> +		DRM_DEBUG_KMS("Backlight control over AUX not supported\n");
> +		return -ENODEV;
> +	}
> +
> +	if (intel_dp->aux_blc_use_lsb)
> +		panel->backlight.max = 0xFFFF;
> +	else
> +		panel->backlight.max = 0xFF;
> +
> +	panel->backlight.min = 0;
> +
> +	panel->backlight.level = intel_dp_aux_get_backlight(connector);
> +	panel->backlight.enabled = get_aux_backlight_enable(&intel_dp->aux);
> +
> +	return 0;
> +}
> +
> +void intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
> +{
> +	struct intel_panel *panel = &intel_connector->panel;
> +
> +	panel->backlight.setup = intel_dp_aux_setup_backlight;
> +	panel->backlight.enable = intel_dp_aux_enable_backlight;
> +	panel->backlight.disable = intel_dp_aux_disable_backlight;
> +	panel->backlight.set = intel_dp_aux_set_backlight;
> +	panel->backlight.get = intel_dp_aux_get_backlight;
> +}
> +
> +bool intel_dp_aux_display_control_capable(struct intel_connector *connector)
> +{
> +	struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
> +	uint8_t dpcd_edp[2] = { 0x0 };
> +
> +	/* Check the  eDP Display control capabilities registers to determine if
> +	 * the panel can support backlight control over the aux channel*/
> +	if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_EDP_GENERAL_CAP_1,
> +			dpcd_edp, sizeof(dpcd_edp)) < 0) {
> +		DRM_DEBUG_KMS("Failed to read DPCD Display Control registers\n");
> +		return false;
> +	}
> +	DRM_DEBUG_KMS("EDP DPCD : %*ph\n", (int) sizeof(dpcd_edp), dpcd_edp);
> +
> +	if (dpcd_edp[0] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAPABLE &&
> +			(dpcd_edp[0] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAPABLE) &&
> +			(dpcd_edp[1] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAPABLE) &&
> +			((read_aux_backlight_mode_set_reg(intel_dp) &
> +					DP_EDP_BACKLIGHT_BRIGHTNESS_CTL_MODE_DPCD_MASK))) {
> +
> +		DRM_DEBUG_KMS("AUX Backlight Control Supported!\n");
> +
> +		if (dpcd_edp[1] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
> +			intel_dp->aux_blc_use_lsb = true;
> +
> +		return true;
> +	}
> +	return false;
> +}
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 35a65ca..dacbc37 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -747,6 +747,7 @@ struct intel_dp {
>  	unsigned long last_power_cycle;
>  	unsigned long last_power_on;
>  	unsigned long last_backlight_off;
> +	bool aux_blc_use_lsb;
>  
>  	struct notifier_block edp_notifier;
>  
> @@ -1221,6 +1222,8 @@ void intel_edp_drrs_invalidate(struct drm_device *dev,
>  		unsigned frontbuffer_bits);
>  void intel_edp_drrs_flush(struct drm_device *dev, unsigned frontbuffer_bits);
>  void hsw_dp_set_ddi_pll_sel(struct intel_crtc_state *pipe_config);
> +bool intel_dp_aux_display_control_capable(struct intel_connector *connector);
> +void intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector);
>  
>  /* intel_dp_mst.c */
>  int intel_dp_mst_encoder_init(struct intel_digital_port *intel_dig_port, int conn_id);
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 9adb62b..04eff34 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -1685,7 +1685,10 @@ intel_panel_init_backlight_funcs(struct intel_panel *panel)
>  	struct drm_device *dev = intel_connector->base.dev;
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  
> -	if (IS_BROXTON(dev)) {
> +	if (intel_connector->base.connector_type == DRM_MODE_CONNECTOR_eDP &&
> +		intel_dp_aux_display_control_capable(intel_connector)) {
> +			intel_dp_aux_init_backlight_funcs(intel_connector);
> +	} else if (IS_BROXTON(dev)) {
>  		panel->backlight.setup = bxt_setup_backlight;
>  		panel->backlight.enable = bxt_enable_backlight;
>  		panel->backlight.disable = bxt_disable_backlight;
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 9ec4716..7367e1a 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -455,16 +455,22 @@
>  # define DP_EDP_14			    0x03
>  
>  #define DP_EDP_GENERAL_CAP_1		    0x701
> +#define DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAPABLE      (1 << 0)
> +#define DP_EDP_BACKLIGHT_AUX_ENABLE_CAPABLE           (1 << 2)
>  
>  #define DP_EDP_BACKLIGHT_ADJUSTMENT_CAP     0x702
> +#define DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAPABLE   (1 << 1)
> +#define DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT        (1 << 2)
>  
>  #define DP_EDP_GENERAL_CAP_2		    0x703
>  
>  #define DP_EDP_GENERAL_CAP_3		    0x704    /* eDP 1.4 */
>  
>  #define DP_EDP_DISPLAY_CONTROL_REGISTER     0x720
> +#define DP_EDP_BACKLIGHT_ENABLE                       (1 << 0)
>  
>  #define DP_EDP_BACKLIGHT_MODE_SET_REGISTER  0x721
> +#define DP_EDP_BACKLIGHT_BRIGHTNESS_CTL_MODE_DPCD_MASK 0x2
>  
>  #define DP_EDP_BACKLIGHT_BRIGHTNESS_MSB     0x722
>  #define DP_EDP_BACKLIGHT_BRIGHTNESS_LSB     0x723

I don't have the spec for this but assume you've tested it.  The code looks ok, my only worry is that some eDP panels might return a DPCD backlight capability but then just ignore the writes.  But I guess we'll find that out soon enough if we land this.

So:
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>

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