Re: [PATCH 6/9] drm/i915/psr: Check if source supports sink specific SU granularity

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

On Mon, Nov 26, 2018 at 04:37:07PM -0800, José Roberto de Souza wrote:
> According to eDP spec, sink can required specific selective update
> granularity that source must comply.
> Here caching the value if required and checking source supports it.
> 
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@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 | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index f763b30f98d9..cbcd85af95bf 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -506,6 +506,7 @@ struct i915_psr {
>  	ktime_t last_exit;
>  	bool sink_not_reliable;
>  	bool irq_aux_error;
> +	u16 su_x_granularity;
>  };
>  
>  enum intel_pch {
> diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> index 7607a58a6ec0..9215c9052381 100644
> --- a/drivers/gpu/drm/i915/intel_psr.c
> +++ b/drivers/gpu/drm/i915/intel_psr.c
> @@ -257,6 +257,21 @@ static u8 intel_dp_get_sink_sync_latency(struct intel_dp *intel_dp)
>  	return val;
>  }
>  
> +static u16 intel_dp_get_su_x_granulartiy(struct intel_dp *intel_dp)
> +{
> +	u16 val = 0;
> +	ssize_t r;
> +
> +	if (!(intel_dp->psr_dpcd[1] & DP_PSR2_SU_GRANULARITY_REQUIRED))
> +		return val;
> +
> +	r = drm_dp_dpcd_read(&intel_dp->aux, DP_PSR2_SU_X_GRANULARITY, &val, 2);
> +	if (r != 2)
> +		DRM_WARN("Unable to read DP_PSR2_SU_X_GRANULARITY\n");
> +
> +	return val;
> +}
> +
>  void intel_psr_init_dpcd(struct intel_dp *intel_dp)
>  {
>  	struct drm_i915_private *dev_priv =
> @@ -311,6 +326,8 @@ void intel_psr_init_dpcd(struct intel_dp *intel_dp)
>  		if (dev_priv->psr.sink_psr2_support) {
>  			dev_priv->psr.colorimetry_support =
>  				intel_dp_get_colorimetry_status(intel_dp);
> +			dev_priv->psr.su_x_granularity =
> +				intel_dp_get_su_x_granulartiy(intel_dp);
>  		}
>  	}
>  }
> @@ -525,6 +542,21 @@ static bool intel_psr2_config_valid(struct intel_dp *intel_dp,
>  		return false;
>  	}
>  
> +	if (dev_priv->psr.su_x_granularity) {
> +		/*
> +		 * HW will always send full lines in SU blocks, so X will
> +		 * always be 0 and we only need to check the width to validate
> +		 * horizontal granularity.
> +		 * About vertical granularity HW works by SU blocks starting
> +		 * at each 4 lines with height of 4 lines, what eDP states
> +		 * that sink should support.
> +		 */
> +		if (crtc_hdisplay % dev_priv->psr.su_x_granularity) {
> +			DRM_DEBUG_KMS("PSR2 not enabled, HW can not match sink SU granularity requirement\n");
> +			return false;


I wonder if regardless this bit we still need to do a sort of
check anyway because spec states:

"
Sets the grid pattern granularity in the X direction.
A value of 0 indicates that no X-coordinate granularity requirement exists other than
the standard restrictions, wherein the:
•
 Starting X-coordinate must be evenly divisible by 16
 •
 Rectangle width must be evenly divisible by 4
"

Also, why we are just checking X granularity and not Y? (0074h)

(maybe it would be useful to introduce along with previous patch
that I had just reviewed)

> +		}
> +	}
> +
>  	return true;
>  }
>  
> -- 
> 2.19.2
> 
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