linux-kernel - RE: Linux 3.8-rc4

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Date:	Thu, 31 Jan 2013 14:56:07 +0000
From:	"Deucher, Alexander" <Alexander.Deucher@....com>
To:	Shuah Khan <shuahkhan@...il.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RE: Linux 3.8-rc4

> -----Original Message-----
> From: Shuah Khan [mailto:shuahkhan@...il.com]
> Sent: Wednesday, January 30, 2013 4:12 PM
> To: Deucher, Alexander
> Cc: Linus Torvalds; Linux Kernel Mailing List
> Subject: Re: Linux 3.8-rc4
> 
> On Wed, Jan 30, 2013 at 8:53 AM, Deucher, Alexander
> <Alexander.Deucher@....com> wrote:
> >> -----Original Message-----
> >> From: Shuah Khan [mailto:shuahkhan@...il.com]
> >> Sent: Wednesday, January 30, 2013 10:35 AM
> >> To: Deucher, Alexander
> >> Cc: Linus Torvalds; Linux Kernel Mailing List
> >> Subject: Re: Linux 3.8-rc4
> >>
> >> On Wed, Jan 30, 2013 at 6:31 AM, Deucher, Alexander
> >> <Alexander.Deucher@....com> wrote:
> >>
> >> >>
> >> >> ok. I did more debugging in rv515_mc_stop() and here is what's
> >> >> happening. It has two display controllers and one of them is enabled
> >> >> and the other is in disabled state when AVIVO_D1CRTC_CONTROL is
> >> >> checked. The current code doesn't blank the disabled crtc. However, it
> >> >> needs to be blanked to avoid DMAR faults it appears. I think that is
> >> >> what the original code prior to
> >> >> 6253e4c75d96006c06b9ac8f417eba873de2497b commit was doing:
> >> >>
> >> >> -       WREG32(R_0060E8_D1CRTC_UPDATE_LOCK, 1);
> >> >> -       WREG32(R_0068E8_D2CRTC_UPDATE_LOCK, 1);
> >> >> -       WREG32(R_006080_D1CRTC_CONTROL, 0);
> >> >> -       WREG32(R_006880_D2CRTC_CONTROL, 0);
> >> >> -       WREG32(R_0060E8_D1CRTC_UPDATE_LOCK, 0);
> >> >> -       WREG32(R_0068E8_D2CRTC_UPDATE_LOCK, 0);
> >> >> -       WREG32(R_000330_D1VGA_CONTROL, 0);
> >> >> -       WREG32(R_000338_D2VGA_CONTROL, 0);
> >> >>
> >> >> Anyways, here is the diff for the change (by no means a patch) I made
> >> >> that fixed the problem:
> >> >
> >> > Unfortunately, that just fixes the problem by causing an additional delay
> >> since the wait_for_vblank() and get_frame_count() loops will timeout
> since
> >> the secondary display is disabled.  The previous code disabled the displays
> >> completely while the new code just disables the memory request
> interface
> >> so that the display timing stays on to avoid additional flicker at startup or
> GPU
> >> reset.  For some reason on your system there seems to be a delay in
> getting
> >> the memory request interface to stop.
> >> >
> >> > Alex
> >>
> >> Right. That makes sense and yes the annoying flicker went away. :) Can
> >> you think of something that can address systems that would need more
> >> time to get the memory request interface to stop such as mine?
> >
> > Does adding an additional radeon_mc_wait_for_idle(rdev) call at the end
> of rv515_mc_stop() help?  Can you find out what the minimum delay
> required for your system is?
> >
> > Alex
> 
> Adding radeon_mc_wait_for_idle(rdev) call at the end of
> rv515_mc_stop() - didn't help.
> 
> I tried with adding udelay() with delay values of 1,10, and 50, and
> 100 at the end of rv515_mc_stop(). 100 is the minimum that fixed the
> DMAR faults.

I guess we can just add the delay.  I've tried all the ways I know of to get proper feedback from the hardware.

Alex


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