Re: [Intel-gfx] [PATCH v2 4/9] drm/i915/display: Handle frontbuffer rendering when PSR2 selective fetch is enabled

[Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>]

On 9/30/21 3:14 AM, José Roberto de Souza wrote:
> When PSR2 selective fetch is enabled writes to CURSURFLIVE alone do
> not causes the panel to be updated when doing frontbuffer rendering.
> 
>  From what I was able to figure from experiments the writes to
> CURSURFLIVE takes PSR2 from deep sleep but panel is not updated
> because PSR2_MAN_TRK_CTL has no start and end region set.
> 
> As we don't have the dirt area from current flush and invalidate API
> and even if we did userspace could do several draws to frontbuffer and
> we would need a way to append all the damaged areas of all the draws
> that need to be part of next frame.
> 
> So here only programing PSR2_MAN_TRK_CTL to do a single full frame
> fetch.
> 
> It is a safe approach as if scanout is in the visible area
> the single full frame will only be visible for hardware in the next
> frame because of the double buffering, and if scanout is in vblank
> area it will be draw in the current frame.
> 
> No need to disable PSR and wait a few miliseconds to enable it again.
> 
> Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_psr.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 8534cbb0d5144..7185801d5deff 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -1397,10 +1397,22 @@ void intel_psr_resume(struct intel_dp *intel_dp)
>   	mutex_unlock(&psr->lock);
>   }
>   
> +static inline u32 man_trk_ctl_single_full_frame_bit_get(struct drm_i915_private *dev_priv)
> +{
> +	return IS_ALDERLAKE_P(dev_priv) ?
> +	       ADLP_PSR2_MAN_TRK_CTL_SF_SINGLE_FULL_FRAME :
> +	       PSR2_MAN_TRK_CTL_SF_SINGLE_FULL_FRAME;
> +}
> +
>   static void psr_force_hw_tracking_exit(struct intel_dp *intel_dp)
>   {
>   	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
>   
> +	if (intel_dp->psr.psr2_sel_fetch_enabled)
> +		intel_de_rmw(dev_priv,
> +			     PSR2_MAN_TRK_CTL(intel_dp->psr.transcoder), 0,
> +			     man_trk_ctl_single_full_frame_bit_get(dev_priv));
> +
>   	/*
>   	 * Display WA #0884: skl+
The following details is described in the description related to Display 
WA #0884, so I think it matches the commit message described above.
  : Driver to issue a flip whenever a host modify occurs. This ensures 
PSR exits its sleep state during a host modify event.

However, it is not clearly stated whether this WA# will also affect 
GEN12+. Since there is a possibility that it may not work normally in HW 
that will be released later, if you don't mind could you please leave a 
comment that this operation has been confirmed in ADLP?

Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
>   	 * This documented WA for bxt can be safely applied
>