Re: [PATCH 1/2] drm/i915: Allow preservation of watermarks.

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

On Tue, Mar 01, 2016 at 11:07:21AM +0100, Maarten Lankhorst wrote:
> As Paulo has noted we can help bisectability by separating computing
> watermarks on a noop in 2 separate commits.
> 
> This patch no longer clears the crtc watermark state, but recalculates
> it completely. Regardless whether a level is used the full values for
> each level are calculated. If a level is invalid wm[level].enable is
> unset.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index d33de954a2e4..1b8ba777d2b3 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2300,7 +2300,7 @@ static int ilk_compute_pipe_wm(struct intel_crtc *intel_crtc,
>  	struct intel_plane_state *pristate = NULL;
>  	struct intel_plane_state *sprstate = NULL;
>  	struct intel_plane_state *curstate = NULL;
> -	int level, max_level = ilk_wm_max_level(dev);
> +	int level, max_level = ilk_wm_max_level(dev), usable_level;
>  	struct ilk_wm_maximums max;
>  
>  	cstate = intel_atomic_get_crtc_state(state, intel_crtc);
> @@ -2308,7 +2308,6 @@ static int ilk_compute_pipe_wm(struct intel_crtc *intel_crtc,
>  		return PTR_ERR(cstate);
>  
>  	pipe_wm = &cstate->wm.optimal.ilk;
> -	memset(pipe_wm, 0, sizeof(*pipe_wm));
>  
>  	for_each_intel_plane_on_crtc(dev, intel_crtc, intel_plane) {
>  		ps = drm_atomic_get_plane_state(state,
> @@ -2330,13 +2329,15 @@ static int ilk_compute_pipe_wm(struct intel_crtc *intel_crtc,
>  		(drm_rect_width(&sprstate->dst) != drm_rect_width(&sprstate->src) >> 16 ||
>  		drm_rect_height(&sprstate->dst) != drm_rect_height(&sprstate->src) >> 16);
>  
> +	usable_level = max_level;
> +
>  	/* ILK/SNB: LP2+ watermarks only w/o sprites */
>  	if (INTEL_INFO(dev)->gen <= 6 && sprstate->visible)
> -		max_level = 1;
> +		usable_level = 1;
>  
>  	/* ILK/SNB/IVB: LP1+ watermarks only w/o scaling */
>  	if (pipe_wm->sprites_scaled)
> -		max_level = 0;
> +		usable_level = 0;
>  
>  	ilk_compute_wm_level(dev_priv, intel_crtc, 0, cstate,
>  			     pristate, sprstate, curstate, &pipe_wm->wm[0]);
> @@ -2350,20 +2351,21 @@ static int ilk_compute_pipe_wm(struct intel_crtc *intel_crtc,
>  	ilk_compute_wm_reg_maximums(dev, 1, &max);
>  
>  	for (level = 1; level <= max_level; level++) {
> -		struct intel_wm_level wm = {};
> +		struct intel_wm_level *wm = &pipe_wm->wm[level];
>  
>  		ilk_compute_wm_level(dev_priv, intel_crtc, level, cstate,
> -				     pristate, sprstate, curstate, &wm);
> +				     pristate, sprstate, curstate, wm);
>  
>  		/*
>  		 * Disable any watermark level that exceeds the
>  		 * register maximums since such watermarks are
>  		 * always invalid.
>  		 */
> -		if (!ilk_validate_wm_level(level, &max, &wm))
> -			break;
> -
> -		pipe_wm->wm[level] = wm;
> +		if (!ilk_validate_wm_level(level, &max, wm)) {
> +			usable_level = level;
> +			wm->enable = false;
> +		} else if (level > usable_level)
> +			wm->enable = false;

That seems to be the wrong way around. I don't think there's
any point in calling ilk_validate_wm_level() if the level
already exceeds the max.

>  	}
>  
>  	return 0;
> -- 
> 2.1.0
> 
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-- 
Ville Syrjälä
Intel OTC
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