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

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Date:	Tue, 3 Nov 2015 23:09:20 +0100
From:	Pavel Machek <pavel@....cz>
To:	Alex Deucher <alexdeucher@...il.com>
Cc:	Christian König <christian.koenig@....com>,
	"Deucher, Alexander" <alexander.deucher@....com>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	kernel list <linux-kernel@...r.kernel.org>,
	Maling list - DRI developers 
	<dri-devel@...ts.freedesktop.org>
Subject: Re: Mobility Radeon HD 4530/4570/545v: flicker in 1920x1080

Hi!

> >> >4.3-rc7 kernel, graphics works reasonably well in 1600x1200 mode. But
> >> >my monitor is native 1920x1080, so that mode looks pretty ugly on
> >> >screen. If I go to 1920x1080, I see colored horizontal lines (often
> >> >black) as soon as there's graphics activity.
> >> >
> >> >pavel@...f:~$ xrandr
> >> >Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
> >> >VGA-0 connected 1920x1080+0+0 (normal left inverted right x axis y
> >> >axis) 478mm x 268mm
> >> >    1920x1080     60.00*+
> >> >       1600x1200     60.00
> >> >          1680x1050     59.95
> >> >         1280x1024     75.02    60.02
> >> >            1440x900      59.89
> >> >               1024x768      75.08    60.00
> >> >                  800x600       75.00    60.32
> >> >                     640x480       75.00    60.00
> >> >                        720x400       70.08
> >> >  pavel@...f:~$ xrandr --output VGA-0 --mode 1600x1200
> >> >  pavel@...f:~$ xrandr --output VGA-0 --mode 1920x1080
> >> >  pavel@...f:~$ xrandr --output VGA-0 --mode 1600x1200
> >> >

> >> >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.

> Unfortunately, it can't be applied as is because we had a similar
> patch which was reverted because it regressed a bunch of other
> systems.  The actual pll limits probably need to be tweaked.

Any ideas how to tweak the pll limits?

Thanks,
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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