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

[Jani Nikula]

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.


[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
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-- 
Jani Nikula, Intel Open Source Technology Center