Re: [PATCH 1/2] drm/i915/gen9: unconditionally apply the memory bandwidth WA

[Lyude <cpaul@redhat.com>]

Reviewed-by: Lyude <cpaul@redhat.com>

On Tue, 2016-10-11 at 15:25 -0300, Paulo Zanoni wrote:
> Mahesh Kumar is already working on a proper implementation for the
> workaround, but while we still don't have it, let's just
> unconditionally apply the workaround for everybody and we hope we can
> close all those numerous bugzilla tickets. Also, I'm not sure how
> easy
> it will be to backport the final implementation to the stable
> Kernels,
> and this patch here is probably easier to backport.
> 
> At the present moment I still don't have confirmation that this patch
> fixes any of the bugs listed below, but we should definitely try
> testing all of them again.
> 
> v2: s/intel_needs_memory_bw_wa/skl_needs_memory_bw_wa/ (Lyude).
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94337
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94605
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94884
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95010
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96226
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96828
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97450
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97830
> Cc: stable@vger.kernel.org
> Cc: Mahesh Kumar <mahesh1.kumar@intel.com>
> Cc: Lyude <cpaul@redhat.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 49
> ++++++++++++++++++++++++++++++++++-------
>  1 file changed, 41 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c
> b/drivers/gpu/drm/i915/intel_pm.c
> index fe6c1c6..13bd974 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2879,6 +2879,21 @@ skl_wm_plane_id(const struct intel_plane
> *plane)
>  	}
>  }
>  
> +/*
> + * FIXME: We still don't have the proper code detect if we need to
> apply the WA,
> + * so assume we'll always need it in order to avoid underruns.
> + */
> +static bool skl_needs_memory_bw_wa(struct intel_atomic_state *state)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(state-
> >base.dev);
> +
> +	if (IS_SKYLAKE(dev_priv) || IS_BROXTON(dev_priv) ||
> +	    IS_KABYLAKE(dev_priv))
> +		return true;
> +
> +	return false;
> +}
> +
>  static bool
>  intel_has_sagv(struct drm_i915_private *dev_priv)
>  {
> @@ -2999,9 +3014,10 @@ bool intel_can_enable_sagv(struct
> drm_atomic_state *state)
>  	struct drm_device *dev = state->dev;
>  	struct drm_i915_private *dev_priv = to_i915(dev);
>  	struct intel_atomic_state *intel_state =
> to_intel_atomic_state(state);
> -	struct drm_crtc *crtc;
> +	struct intel_crtc *crtc;
> +	struct intel_plane *plane;
>  	enum pipe pipe;
> -	int level, plane;
> +	int level, id, latency;
>  
>  	if (!intel_has_sagv(dev_priv))
>  		return false;
> @@ -3019,27 +3035,36 @@ bool intel_can_enable_sagv(struct
> drm_atomic_state *state)
>  
>  	/* Since we're now guaranteed to only have one active
> CRTC... */
>  	pipe = ffs(intel_state->active_crtcs) - 1;
> -	crtc = dev_priv->pipe_to_crtc_mapping[pipe];
> +	crtc = to_intel_crtc(dev_priv->pipe_to_crtc_mapping[pipe]);
>  
> -	if (crtc->state->mode.flags & DRM_MODE_FLAG_INTERLACE)
> +	if (crtc->base.state->mode.flags & DRM_MODE_FLAG_INTERLACE)
>  		return false;
>  
> -	for_each_plane(dev_priv, pipe, plane) {
> +	for_each_intel_plane_on_crtc(dev, crtc, plane) {
> +		id = skl_wm_plane_id(plane);
> +
>  		/* Skip this plane if it's not enabled */
> -		if (intel_state->wm_results.plane[pipe][plane][0] ==
> 0)
> +		if (intel_state->wm_results.plane[pipe][id][0] == 0)
>  			continue;
>  
>  		/* Find the highest enabled wm level for this plane
> */
>  		for (level = ilk_wm_max_level(dev);
> -		     intel_state-
> >wm_results.plane[pipe][plane][level] == 0; --level)
> +		     intel_state->wm_results.plane[pipe][id][level]
> == 0; --level)
>  		     { }
>  
> +		latency = dev_priv->wm.skl_latency[level];
> +
> +		if (skl_needs_memory_bw_wa(intel_state) &&
> +		    plane->base.state->fb->modifier[0] ==
> +		    I915_FORMAT_MOD_X_TILED)
> +			latency += 15;
> +
>  		/*
>  		 * If any of the planes on this pipe don't enable wm
> levels
>  		 * that incur memory latencies higher then 30µs we
> can't enable
>  		 * the SAGV
>  		 */
> -		if (dev_priv->wm.skl_latency[level] <
> SKL_SAGV_BLOCK_TIME)
> +		if (latency < SKL_SAGV_BLOCK_TIME)
>  			return false;
>  	}
>  
> @@ -3555,12 +3580,18 @@ static int skl_compute_plane_wm(const struct
> drm_i915_private *dev_priv,
>  	uint32_t width = 0, height = 0;
>  	uint32_t plane_pixel_rate;
>  	uint32_t y_tile_minimum, y_min_scanlines;
> +	struct intel_atomic_state *state =
> +		to_intel_atomic_state(cstate->base.state);
> +	bool apply_memory_bw_wa = skl_needs_memory_bw_wa(state);
>  
>  	if (latency == 0 || !cstate->base.active || !intel_pstate-
> >base.visible) {
>  		*enabled = false;
>  		return 0;
>  	}
>  
> +	if (apply_memory_bw_wa && fb->modifier[0] ==
> I915_FORMAT_MOD_X_TILED)
> +		latency += 15;
> +
>  	width = drm_rect_width(&intel_pstate->base.src) >> 16;
>  	height = drm_rect_height(&intel_pstate->base.src) >> 16;
>  
> @@ -3613,6 +3644,8 @@ static int skl_compute_plane_wm(const struct
> drm_i915_private *dev_priv,
>  				 plane_blocks_per_line);
>  
>  	y_tile_minimum = plane_blocks_per_line * y_min_scanlines;
> +	if (apply_memory_bw_wa)
> +		y_tile_minimum *= 2;
>  
>  	if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
>  	    fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
-- 
Cheers,
	Lyude