Re: [PATCH 04/12] drm/i915/psr: Tie PSR2 support to Y coordinate requirement

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Mar 22, 2018 at 02:48:40PM -0700, José Roberto de Souza wrote:
> Move to only one place the sink requirements that the actual driver
> needs to enable PSR2.
> 
> Also intel_psr2_config_valid() is called every time the crtc config
> is computed, wasting some time every time it was checking for
> Y coordinate requirement.
> 
> This allow us to nuke y_cord_support and some of VSC setup code that
> was handling a scenario that would never happen(PSR2 without Y
> coordinate).
> 
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h  |  1 -
>  drivers/gpu/drm/i915/intel_psr.c | 46 +++++++++++++++++-----------------------
>  2 files changed, 19 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 7fe00509e51a..cce32686fd75 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -603,7 +603,6 @@ struct i915_psr {
>  	unsigned busy_frontbuffer_bits;
>  	bool psr2_support;
>  	bool link_standby;
> -	bool y_cord_support;
>  	bool colorimetry_support;
>  	bool alpm;
>  	bool has_hw_tracking;
> diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> index d46320a451d9..23f38ab10636 100644
> --- a/drivers/gpu/drm/i915/intel_psr.c
> +++ b/drivers/gpu/drm/i915/intel_psr.c
> @@ -93,7 +93,7 @@ static void psr_aux_io_power_put(struct intel_dp *intel_dp)
>  	intel_display_power_put(dev_priv, psr_aux_domain(intel_dp));
>  }
>  
> -static bool intel_dp_get_y_cord_status(struct intel_dp *intel_dp)
> +static bool intel_dp_get_y_coord_required(struct intel_dp *intel_dp)

nip: I don't agree that required is a good name for this function call
so maybe we should just leave status and minimize the change.

>  {
>  	uint8_t psr_caps = 0;
>  
> @@ -130,22 +130,29 @@ void intel_psr_init_dpcd(struct intel_dp *intel_dp)
>  	drm_dp_dpcd_read(&intel_dp->aux, DP_PSR_SUPPORT, intel_dp->psr_dpcd,
>  			 sizeof(intel_dp->psr_dpcd));
>  
> -	if (intel_dp->psr_dpcd[0] & DP_PSR_IS_SUPPORTED) {
> +	if (intel_dp->psr_dpcd[0]) {

hm? why?

>  		dev_priv->psr.sink_support = true;
>  		DRM_DEBUG_KMS("Detected EDP PSR Panel.\n");
>  	}
>  
>  	if (INTEL_GEN(dev_priv) >= 9 &&
> -	    (intel_dp->psr_dpcd[0] & DP_PSR2_IS_SUPPORTED)) {
> -
> -		dev_priv->psr.sink_support = true;
> -		dev_priv->psr.psr2_support = true;
> +	    (intel_dp->psr_dpcd[0] == DP_PSR2_WITH_Y_COORD_IS_SUPPORTED)) {
> +		/*
> +		 * All panels that supports PSR version 03h (PSR2 +
> +		 * Y-coordinate) can handle Y-coordinates in VSC but we are
> +		 * only sure that it is going to be used when required by the
> +		 * panel. This way panel is capable to do selective update
> +		 * without a aux frame sync.
> +		 *
> +		 * To support PSR version 02h and PSR version 03h without
> +		 * Y-coordinate requirement panels we would need to enable
> +		 * GTC first.
> +		 */
> +		dev_priv->psr.psr2_support = intel_dp_get_y_coord_required(intel_dp);

oh ok ok... now I saw why you changed to "required"

But my question now is. Do we really need to check this bit?

I believe with your change to check version 03h we don't need to check
this requirement anymore.
This looks like in the past we used that to workaround a way to identify
if the panel was really y-coord... but now with 03h version we don't need
to check if panel is requiring the y-coordination from the source, because
we know what source is capable of.

>  		DRM_DEBUG_KMS("PSR2 %s on sink",
>  			      dev_priv->psr.psr2_support ? "supported" : "not supported");
>  
>  		if (dev_priv->psr.psr2_support) {
> -			dev_priv->psr.y_cord_support =
> -				intel_dp_get_y_cord_status(intel_dp);
>  			dev_priv->psr.colorimetry_support =
>  				intel_dp_get_colorimetry_status(intel_dp);
>  			dev_priv->psr.alpm =
> @@ -191,16 +198,12 @@ static void hsw_psr_setup_vsc(struct intel_dp *intel_dp,
>  		memset(&psr_vsc, 0, sizeof(psr_vsc));
>  		psr_vsc.sdp_header.HB0 = 0;
>  		psr_vsc.sdp_header.HB1 = 0x7;
> -		if (dev_priv->psr.colorimetry_support &&
> -		    dev_priv->psr.y_cord_support) {
> +		if (dev_priv->psr.colorimetry_support) {
>  			psr_vsc.sdp_header.HB2 = 0x5;
>  			psr_vsc.sdp_header.HB3 = 0x13;
> -		} else if (dev_priv->psr.y_cord_support) {
> +		} else {
>  			psr_vsc.sdp_header.HB2 = 0x4;
>  			psr_vsc.sdp_header.HB3 = 0xe;
> -		} else {
> -			psr_vsc.sdp_header.HB2 = 0x3;
> -			psr_vsc.sdp_header.HB3 = 0xc;
>  		}
>  	} else {
>  		/* Prepare VSC packet as per EDP 1.3 spec, Table 3.10 */
> @@ -458,15 +461,6 @@ static bool intel_psr2_config_valid(struct intel_dp *intel_dp,
>  		return false;
>  	}
>  
> -	/*
> -	 * FIXME:enable psr2 only for y-cordinate psr2 panels
> -	 * After gtc implementation , remove this restriction.
> -	 */
> -	if (!dev_priv->psr.y_cord_support) {
> -		DRM_DEBUG_KMS("PSR2 not enabled, panel does not support Y coordinate\n");
> -		return false;
> -	}
> -
>  	return true;
>  }
>  
> @@ -566,7 +560,6 @@ static void hsw_psr_enable_source(struct intel_dp *intel_dp,
>  	struct drm_device *dev = dig_port->base.base.dev;
>  	struct drm_i915_private *dev_priv = to_i915(dev);
>  	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> -	u32 chicken;
>  
>  	psr_aux_io_power_get(intel_dp);
>  
> @@ -577,9 +570,8 @@ static void hsw_psr_enable_source(struct intel_dp *intel_dp,
>  		hsw_psr_setup_aux(intel_dp);
>  
>  	if (dev_priv->psr.psr2_support) {
> -		chicken = PSR2_VSC_ENABLE_PROG_HEADER;
> -		if (dev_priv->psr.y_cord_support)
> -			chicken |= PSR2_ADD_VERTICAL_LINE_COUNT;
> +		u32 chicken = PSR2_VSC_ENABLE_PROG_HEADER
> +			      | PSR2_ADD_VERTICAL_LINE_COUNT;
>  		I915_WRITE(CHICKEN_TRANS(cpu_transcoder), chicken);
>  
>  		I915_WRITE(EDP_PSR_DEBUG,
> -- 
> 2.16.2
> 
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