Re: [PATCH 23/24] drm/i915: Add a workaround for sprite only <-> primary only switching

Daniel Vetter
2014-03-07T21:32:59Z

On Fri, Mar 07, 2014 at 06:32:30PM +0200, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> ILK and IVB don't like switching between sprite only and primary only
> configurations when LP1+ watermarks have been enabled in the recent
> past. Like WaCxSRDisabledForSpriteScaling we can avoid the flash
> by disabling LP1+ watermarks for one frame before the critical plane
> reconfiguration.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index ddf77d5..c011da5 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3127,9 +3127,18 @@ static int ilk_update_sprite_wm(struct drm_plane *plane,
> * when scaling is disabled.
> *
> * WaCxSRDisabledForSpriteScaling:ivb
> + *
> + * We also seem to need something similar when switching between
> + * primary only and sprite only configurations. Otherwise the screen
> + * flashes black. No underrun reported though.
> */
> if (IS_IVYBRIDGE(dev) && config->spr.scaled && ilk_disable_lp_wm(crtc))
> intel_wait_for_vblank(dev, to_intel_plane(plane)->pipe);
> + else if (config->pri.enabled != config->spr.enabled &&
> + config->pri.enabled != params.pri.enabled &&
> + config->spr.enabled != params.spr.enabled &&
> + ilk_disable_lp_wm(crtc))

I think it would help readability a bit to extract this monster condition
into a tiny helper with descriptive name ... just my bikeshed of the day.
-Daniel

> + intel_wait_for_vblank(dev, to_intel_plane(plane)->pipe);
>
> params.pri = config->pri;
> params.spr = config->spr;
> --
> 1.8.3.2
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch