[Intel-gfx] [PATCH] drm/i915: Don't do pre plane update on disabled crtcs

[Ville Syrjälä]

On Thu, Jan 14, 2016 at 06:32:10PM +0200, Mika Kuoppala wrote:
> CI/Bat got following (shortened) trace on byt and also
> on bsw:
> 
> ------------[ cut here ]-----------
> Unclaimed register detected before reading register 0x186500
> Call Trace:
>  __unclaimed_reg_debug+0x68/0x80 [i915]
> vlv_read32+0x2de/0x370 [i915]
> intel_set_memory_cxsr+0x87/0x1a0 [i915]
> intel_pre_plane_update+0xb3/0xf0 [i915]
> intel_atomic_commit+0x3b5/0x17c0 [i915]
> ...
> ---[ end trace 6387a0ad001bb39f ]---
> 
> Fix this by limiting pre plane update only to active crtcs.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=93698
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index aa24f79d85bf..a134a698d97d 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -13580,9 +13580,8 @@ static int intel_atomic_commit(struct drm_device *dev,
>  		if (!needs_modeset(crtc->state))
>  			continue;
>  
> -		intel_pre_plane_update(intel_crtc);
> -
>  		if (crtc_state->active) {
> +			intel_pre_plane_update(intel_crtc);

I think you'll want to deal with the other one too (the one in the crtc
enable/plane update path). Actually I think the plane update stuff
should be split into a separate loop from the crtc_enable stuff, but
that's a separate topic.

Hmm. And there's a post_plane_update there that looks a bit too
lonely as well. Something really should be done to make this code
less convoluted. A modeset/plane update shouldn't be this hard to
get right.

>  			intel_crtc_disable_planes(crtc, crtc_state->plane_mask);
>  			dev_priv->display.crtc_disable(crtc);
>  			intel_crtc->active = false;
> -- 
> 2.5.0

-- 
Ville Syrjälä
Intel OTC