linux-kernel - Re: Mobility Radeon HD 4530/4570/545v: flicker in 1920x1080

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Date:	Wed, 4 Nov 2015 08:36:32 +0100
From:	Christian König <deathsimple@...afone.de>
To:	Pavel Machek <pavel@....cz>, Alex Deucher <alexdeucher@...il.com>
Cc:	"Deucher, Alexander" <alexander.deucher@....com>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	Christian König <christian.koenig@....com>,
	Maling list - DRI developers 
	<dri-devel@...ts.freedesktop.org>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: Mobility Radeon HD 4530/4570/545v: flicker in 1920x1080

On 04.11.2015 00:03, Pavel Machek wrote:
> Hi!
>
>
>>>>>>> Any ideas?
>>>>>> Alex probably knows more about this, but it sounds like problems with
>>>>>> switching the memory clocks on 3D load.
>>>>>> Try to disable power management completely with radeon.dpm=0 on the kernel
>>>>>> command line or nailing the hardware at a specific power level using
>>>>>> sysfs.
>>>>> I tried that, but it still flickers.
>>>> It's probably pll stability.  There seem to be a number of regressions
>>>> since the pll code was rewritten to support matching the hdmi clocks
>>>> more closely.  Does this patch help?
>>>>
>>>> diff --git a/drivers/gpu/drm/radeon/atombios_crtc.c
>>>> b/drivers/gpu/drm/radeon/atombios_crtc.c
>>>> index dac78ad..b86f06a 100644
>>>> --- a/drivers/gpu/drm/radeon/atombios_crtc.c
>>>> +++ b/drivers/gpu/drm/radeon/atombios_crtc.c
>>>> @@ -569,6 +569,8 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
>>>>          radeon_crtc->pll_flags = 0;
>>>>
>>>>          if (ASIC_IS_AVIVO(rdev)) {
>>>> +               radeon_crtc->pll_flags |= RADEON_PLL_PREFER_MINM_OVER_MAXP;
>>>> +
>>>>                  if ((rdev->family == CHIP_RS600) ||
>>>>                      (rdev->family == CHIP_RS690) ||
>>>>                      (rdev->family == CHIP_RS740))
>>>>
>>> Help.. maybe... it is tricky to tell. It definitely does _not_ fix the
>>> issue completely.
>> You could also try the old pll algorithm:
> I reverted the patch above, and switched to the old algorithm.
>
> The flicker is still there. (But maybe its less horrible, like with
> RADEON_PLL_PREFER_MINM_OVER_MAXP).

The flickering would vanish completely if that's the reason for the 
issue you are seeing.

Try setting ref_div_min and ref_div_max to 2 in radeon_compute_pll_avivo().

But I'm not 100% convinced that this is actually a PLL problem, try to 
compile the firmware it complains about into the kernel as well.

Regards,
Christian.

>
> Thanks,
> 								Pavel
> 								

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