[Intel-gfx] [PATCH] drm/i915: Fix screen flickering on X

[Jani Nikula]

On Thu, 07 May 2015, Matt Roper <matthew.d.roper at intel.com> wrote:
> On Thu, May 07, 2015 at 12:12:18PM +0300, Jani Nikula wrote:
>> On Thu, 23 Apr 2015, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>> > [cc'ing the authors]
>> 
>> This has been posted earlier [1] and it has review to be addressed [2].
>> 
>> BR,
>> Jani.
>
> I agree with Ander's response in [2]...we can't call
> intel_update_watermarks() in the commit function because we're under
> vblank evasion.  We should already be flagging the transaction as
> needing a watermark update in intel_check_cursor_plane(), and that flag
> will be acted upon immediately after the commit functions are done
> running, once we've re-enabled interrupts.
>
> Note that our current codebase looks a bit different since we've dropped
> intel_crtc->cursor_{width,height}.  So the relevant check in
> intel_check_cursor_plane() now looks like:
>
>         if (plane->state->crtc_w != state->base.crtc_w)
>                 intel_crtc->atomic.update_wm = true;
>
> Is there a bugzilla open on this issue with more details?

Not that I know of. Ismael?

BR,
Jani.


>
>
> Matt
>
>> 
>> 
>> [1] http://mid.gmane.org/1428790644-6812-1-git-send-email-ismael@iodev.co.uk
>> [2] http://mid.gmane.org/1428928418.2654.8.camel@gmail.com
>> 
>> 
>> >
>> > On Sat, Apr 11, 2015 at 07:40:34PM -0300, Ismael Luceno wrote:
>> >> A bisect showed that commit 32b7eeec4d1e861230b09d437e95d76c86ff4a68
>> >> introduced the issue.
>> >> 
>> >> The issue starts as soon as X takes control of the screen, even if just
>> >> a plain X doing nothing, so based on the code touched by the commit I
>> >> thought it had to be related to the so called "hardware cursor". I
>> >> confirmed it when hiding the cursor made the flickering go away.
>> >> 
>> >> The aforementioned commit removed some suspicious code, and the
>> >> Programmer's Reference Manual confirmed my suspicion:
>> >> 
>> >> "Incorrectly programmed watermark values can result in screen corruption.
>> >> 
>> >> The watermarks should be calculated and programmed when any of the
>> >> watermark calculation inputs change. This includes planes enabling or
>> >> disabling, plane source format or size changing, etc."
>> >> 
>> >> So I'm re-adding the few lines that update the watermarks after a cursor
>> >> size change.
>> >> 
>> >> Signed-off-by: Ismael Luceno <ismael at iodev.co.uk>
>> >> ---
>> >>  drivers/gpu/drm/i915/intel_display.c | 7 ++++++-
>> >>  1 file changed, 6 insertions(+), 1 deletion(-)
>> >> 
>> >> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>> >> index f75173c..e23f062 100644
>> >> --- a/drivers/gpu/drm/i915/intel_display.c
>> >> +++ b/drivers/gpu/drm/i915/intel_display.c
>> >> @@ -12258,6 +12258,7 @@ intel_commit_cursor_plane(struct drm_plane *plane,
>> >>  	struct intel_crtc *intel_crtc;
>> >>  	struct intel_plane *intel_plane = to_intel_plane(plane);
>> >>  	struct drm_i915_gem_object *obj = intel_fb_obj(state->base.fb);
>> >> +	unsigned old_width;
>> >>  	uint32_t addr;
>> >>  
>> >>  	crtc = crtc ? crtc : plane->crtc;
>> >> @@ -12282,11 +12283,15 @@ intel_commit_cursor_plane(struct drm_plane *plane,
>> >>  	intel_crtc->cursor_addr = addr;
>> >>  	intel_crtc->cursor_bo = obj;
>> >>  update:
>> >> +	old_width = intel_crtc->cursor_width;
>> >>  	intel_crtc->cursor_width = state->base.crtc_w;
>> >>  	intel_crtc->cursor_height = state->base.crtc_h;
>> >>  
>> >> -	if (intel_crtc->active)
>> >> +	if (intel_crtc->active) {
>> >> +		if (old_width != intel_crtc->cursor_width)
>> >> +			intel_update_watermarks(crtc);
>> >>  		intel_crtc_update_cursor(crtc, state->visible);
>> >> +	}
>> >>  }
>> >>  
>> >>  static struct drm_plane *intel_cursor_plane_create(struct drm_device *dev,
>> >> -- 
>> >> 2.3.4
>> >
>> > -- 
>> > Chris Wilson, Intel Open Source Technology Centre
>> > _______________________________________________
>> > Intel-gfx mailing list
>> > Intel-gfx at lists.freedesktop.org
>> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>> 
>> -- 
>> Jani Nikula, Intel Open Source Technology Center
>
> -- 
> Matt Roper
> Graphics Software Engineer
> IoTG Platform Enabling & Development
> Intel Corporation
> (916) 356-2795

-- 
Jani Nikula, Intel Open Source Technology Center