Re: [Intel-gfx] [PATCH v2 6/9] drm/i915/display/adlp: Optimize PSR2 power-savings in corner cases

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

On 9/30/21 3:14 AM, José Roberto de Souza wrote:
> The Wa_14014971508 is required to fix scanout when a feature that i915
> do not support is enabled and this feature is not planned to be enabled
> for adlp.
> 
> Keeping this workaround enabled can badly hurt power-savings when
> a full frame fetch is required(see psr2_sel_fetch_plane_state_supported()
> and psr2_sel_fetch_pipe_state_supported()).
> 
> Here a example that could badly hurt power-savings, userspace does
> a page flip to a rotated plane, so CONTINUOS_FULL_FRAME set.
> But then for a whole 30 seconds nothing in the screen requires updates
> but because CONTINUOS_FULL_FRAME is set, it will not go into DC5/DC6.
> 
> Reverting Wa_14014971508 fixes that, as only a single frame will be
> sent and then display can go to DC5/DC6 for those 30 seconds of
> idleness.
> 
And add a little more explanation here.
DC6v is a power saving state where the display engine is powered off 
when display enters PSR2 in the video playback.
And the Wa_14014971508 related to DC6v.

Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>

> BSpec: 54369
> Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_psr.c | 11 +++--------
>   1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index e8af39591dfea..b37f123fe0c97 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -1499,15 +1499,10 @@ static void psr2_man_trk_ctl_calc(struct intel_crtc_state *crtc_state,
>   
>   	if (full_update) {
>   		/*
> -		 * Wa_14014971508:adlp
> -		 * SINGLE_FULL_FRAME bit is not hold in register so can not be
> -		 * restored by DMC, so using CONTINUOS_FULL_FRAME to mimic that
> +		 * Not applying Wa_14014971508:adlp as we do not support the
> +		 * feature that requires this workaround.
>   		 */
> -		if (IS_ALDERLAKE_P(dev_priv))
> -			val |= ADLP_PSR2_MAN_TRK_CTL_SF_CONTINUOS_FULL_FRAME;
> -		else
> -			val |= PSR2_MAN_TRK_CTL_SF_SINGLE_FULL_FRAME;
> -
> +		val |= man_trk_ctl_single_full_frame_bit_get(dev_priv);
>   		goto exit;
>   	}
>   
>