Re: [Intel-gfx] [PATCH v1 1/2] drm/i915/xe2lpd: check selective fetch is optimal in some cases

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Nov 02, 2023 at 11:55:18PM +0200, Vinod Govindapillai wrote:
> If both PSR2 + FBC is supported, in cases where the selective
> fetch area is greater than 25% of the screen area, FBC might
> be more efficient.

"might be more efficient" is a very weak justification.

This sort of stuff would really need to be accompanied by 
some actual power numbers (for some actually reasonable
workloads) to justify the extra complication.

> So have a possibility to check this and add
> provision to enable FBC in such cases.
> 
> Bspec: 68881
> Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
> ---
>  .../drm/i915/display/intel_display_types.h    |  1 +
>  drivers/gpu/drm/i915/display/intel_psr.c      | 42 ++++++++++++++++---
>  2 files changed, 38 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 047fe3f8905a..bcc5fd8d8a00 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1207,6 +1207,7 @@ struct intel_crtc_state {
>  	bool has_psr;
>  	bool has_psr2;
>  	bool enable_psr2_sel_fetch;
> +	bool full_frame_fetch;
>  	bool req_psr2_sdp_prior_scanline;
>  	bool wm_level_disabled;
>  	u32 dc3co_exitline;
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index ecd24a0b86cb..6cb32fd29d10 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -1987,10 +1987,35 @@ static bool psr2_sel_fetch_pipe_state_supported(const struct intel_crtc_state *c
>  	return true;
>  }
>  
> +/*
> + * Check selective fetch is optimum
> + *
> + * Compare selective fetch area w.r.t screen size in case both FBC and PSR2
> + * is supported. If the selective fetch area is more than 25% of screen
> + * size, FBC is might be more efficient than PSR2. So force full frame
> + * update.
> + */
> +static bool psr2_sel_fetch_not_optimal(struct drm_i915_private *i915,
> +				       struct drm_rect *sel_fetch,
> +				       struct drm_rect *src)
> +{
> +	int screen_area, selfetch_area;
> +
> +	/* This is needed where FBC + PSR can be supported */
> +	if (DISPLAY_VER(i915) < 20 || !i915->display.params.enable_fbc ||
> +	    !HAS_FBC(i915))
> +		return false;
> +
> +	selfetch_area = drm_rect_height(sel_fetch) * drm_rect_width(sel_fetch);
> +	screen_area = drm_rect_height(src) * drm_rect_width(src);
> +
> +	return DIV_ROUND_CLOSEST(screen_area, selfetch_area) <= 4;
> +}
> +
>  int intel_psr2_sel_fetch_update(struct intel_atomic_state *state,
>  				struct intel_crtc *crtc)
>  {
> -	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> +	struct drm_i915_private *i915 = to_i915(state->base.dev);
>  	struct intel_crtc_state *crtc_state = intel_atomic_get_new_crtc_state(state, crtc);
>  	struct drm_rect pipe_clip = { .x1 = 0, .y1 = -1, .x2 = INT_MAX, .y2 = -1 };
>  	struct intel_plane_state *new_plane_state, *old_plane_state;
> @@ -2082,7 +2107,7 @@ int intel_psr2_sel_fetch_update(struct intel_atomic_state *state,
>  	 * calculation for those.
>  	 */
>  	if (pipe_clip.y1 == -1) {
> -		drm_info_once(&dev_priv->drm,
> +		drm_info_once(&i915->drm,
>  			      "Selective fetch area calculation failed in pipe %c\n",
>  			      pipe_name(crtc->pipe));
>  		full_update = true;
> @@ -2092,9 +2117,9 @@ int intel_psr2_sel_fetch_update(struct intel_atomic_state *state,
>  		goto skip_sel_fetch_set_loop;
>  
>  	/* Wa_14014971492 */
> -	if ((IS_DISPLAY_IP_STEP(dev_priv, IP_VER(14, 0), STEP_A0, STEP_B0) ||
> -	     IS_ALDERLAKE_P(dev_priv) || IS_TIGERLAKE(dev_priv)) &&
> -	    crtc_state->splitter.enable)
> +	if ((IS_DISPLAY_IP_STEP(i915, IP_VER(14, 0), STEP_A0, STEP_B0) ||
> +	     IS_ALDERLAKE_P(i915) || IS_TIGERLAKE(i915)) &&
> +	     crtc_state->splitter.enable)
>  		pipe_clip.y1 = 0;
>  
>  	ret = drm_atomic_add_affected_planes(&state->base, &crtc->base);
> @@ -2149,7 +2174,14 @@ int intel_psr2_sel_fetch_update(struct intel_atomic_state *state,
>  		}
>  	}
>  
> +	if (full_update)
> +		goto skip_sel_fetch_set_loop;
> +
> +	full_update = psr2_sel_fetch_not_optimal(i915, &pipe_clip,
> +						 &crtc_state->pipe_src);
> +
>  skip_sel_fetch_set_loop:
> +	crtc_state->full_frame_fetch = full_update;
>  	psr2_man_trk_ctl_calc(crtc_state, &pipe_clip, full_update);
>  	return 0;
>  }
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel