[Intel-gfx] [PATCH] drm/i915: Pretend cursor is always on for ILK-style WM calculations

[Manfred G Kitzbichler]

I can confirm that the proposed patch fixes the flicker problem on my 
system (openSuse Factory kernel 4.4.0-2-default), even though I had to 
slightly modify it to apply it to the current openSuse Factory sources).



On 02/01/2016 02:22 PM, Ville Syrjälä wrote:
> On Mon, Feb 01, 2016 at 01:26:14AM -0800, Matt Roper wrote:
>> Due to our lack of two-step watermark programming, our driver has
>> historically pretended that the cursor plane is always on for the
>> purpose of watermark calculations; this helps avoid serious flickering
>> when the cursor turns off/on (e.g., when the user moves the mouse
>> pointer to a different screen).  That workaround was accidentally
>> dropped as we started working toward atomic watermark updates.  Since we
>> still aren't quite there yet with two-stage updates, we need to
>> resurrect the workaround and treat the cursor as always active.
>>
>> Cc: simdev11 at outlook.com
>> Cc: manfred.kitzbichler at gmail.com
>> Reported-by: simdev11 at outlook.com
>> Reported-by: manfred.kitzbichler at gmail.com
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93892
>> Fixes: 43d59eda1 ("drm/i915: Eliminate usage of plane_wm_parameters from ILK-style WM code (v2)")
>> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
>> ---
>> I'm traveling at the moment and don't have any HW access, so this patch is
>> completely untested, but I think it will solve the issue being reported.
>>
>>   drivers/gpu/drm/i915/intel_pm.c | 15 ++++++++++-----
>>   1 file changed, 10 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index 31bc4ea..a53c018 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>> @@ -1799,16 +1799,21 @@ static uint32_t ilk_compute_cur_wm(const struct intel_crtc_state *cstate,
>>   				   const struct intel_plane_state *pstate,
>>   				   uint32_t mem_value)
>>   {
>> -	int cpp = pstate->base.fb ?
>> -		drm_format_plane_cpp(pstate->base.fb->pixel_format, 0) : 0;
>> +	/*
>> +	 * We treat the cursor plane as always-on for the purposes of watermark
>> +	 * calculation.  Until we have two-stage watermark programming merged,
>> +	 * this is necessary to avoid flickering.
>> +	 */
>> +	int cpp = 4;
>> +	int width = drm_rect_width(&pstate->dst) ?: 64;
> I don't think we can rely on that being correct when the plane is not
> visible. Also for the cursor, I'm not sure we should be even using the
> visible width of the plane when it's partially visible.
>
>>   
>> -	if (!cstate->base.active || !pstate->visible)
>> +	if (!cstate->base.active)
>>   		return 0;
>>   
>> +
>>   	return ilk_wm_method2(ilk_pipe_pixel_rate(cstate),
>>   			      cstate->base.adjusted_mode.crtc_htotal,
>> -			      drm_rect_width(&pstate->dst),
>> -			      cpp, mem_value);
>> +			      width, cpp, mem_value);
>>   }
>>   
>>   /* Only for WM_LP. */
>> -- 
>> 2.1.4
>>
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