On Mon, Aug 11, 2014 at 01:15:36PM +0300, ville.syrjala@xxxxxxxxxxxxxxx wrote:
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> During suspend we turn off the crtcs, but leave the staged config in
> place so that we can restore the display(s) to their previous state on
> resume.
>
> During resume when we attempt to apply the force pipe A quirk we use the
> load detect mechanism. That doesn't check whether there was an already
> staged configuration for the crtc since that's not even possible during
> normal runtime load detection. But during resume it is possible, and if
> we just blindly go and overwrite the staged crtc configuration for the
> load detection we can no longer restore the display to the correct
> state.
>
> Even worse, we don't even clear all the staged connector->encoder->crtc
> links so we may end up using a cloned setup for the load detection, and
> after we're done we just clear the links related to the VGA output
> leaving the links for the other outputs in place. This will eventually
> result in calling intel_set_mode() with mode==NULL but with valid
> connector->encoder->crtc links which will result in dereferencing the
> NULL mode since the code thinks it will have to a modeset.
>
> To avoid these problems don't use any crtc with new_enabled==true for
> load detection.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
> ---
> drivers/gpu/drm/i915/intel_display.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 7953b46..ec12e31d1 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -8478,10 +8478,14 @@ retry:
> i++;
> if (!(encoder->possible_crtcs & (1 << i)))
> continue;
> - if (!possible_crtc->enabled) {
> - crtc = possible_crtc;
> - break;
> - }
> + if (possible_crtc->enabled)
> + continue;
> + /* This can occur when applying the pipe A quirk on resume. */
> + if (to_intel_crtc(possible_crtc)->new_enabled)
> + continue;
> +
> + crtc = possible_crtc;
> + break;
> }
>
> /*
> --
> 1.8.5.5
>
> _______________________________________________
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--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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