linux-kernel - Re: Linux 2.6.39-rc3

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Date:	Thu, 14 Apr 2011 19:07:34 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Yinghai Lu <yinghai@...nel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Alex Deucher <alexdeucher@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org,
	Thomas Gleixner <tglx@...utronix.de>, Tejun Heo <tj@...nel.org>
Subject: Re: Linux 2.6.39-rc3

On Thu, Apr 14, 2011 at 6:56 PM, Joerg Roedel <joro@...tes.org> wrote:
> On Wed, Apr 13, 2011 at 06:58:46PM -0700, H. Peter Anvin wrote:
>> On 04/13/2011 12:14 PM, Yinghai Lu wrote:
>> >
>> > so looks bios program wrong address to the radon card?
>> >
>>
>> Okay, staring at this, it definitely seems toxic to overlay the GART
>> over memory areas reserved by the BIOS.  If I were to guess, I would say
>> that the problem here seems to be that the kernel thinks it is
>> overlaying 64 MiB of memory, but the actual GART is in fact 512 MiB in
>> size -- 131072 CPU pages -- which now overlaps the BIOS reserved areas.
>>
>> Alex D., could you comment on the "num cpu pages" bit?
>
> Okay, I tried the debug-patch from Yinghai (posted to the bugzilla):
>
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -325,6 +325,8 @@ void radeon_gtt_location(struct radeon_device *rdev, struct radeon_mc *mc)
>                        mc->gtt_size = size_bf;
>                }
>                mc->gtt_start = (mc->vram_start & ~mc->gtt_base_align) - mc->gtt_size;
> +               if (mc->gtt_start == 0xa0000000)
> +                       mc->gtt_start = 0x80000000;
>        } else {
>                if (mc->gtt_size > size_af) {
>                        dev_warn(rdev->dev, "limiting GTT\n");
>
> And this makes a difference, with this change on-top of -rc3 the box boots
> fine. So there seems to be some dependency between the GART base and the GTT
> base even when they are in different address spaces.
>
> Alex, can you comment on this?

Wierd either a hw bug or some access to the GTT is leaking out before,
things are setup properly,

I think the RS780/880 docs are on the website, but generally the
address spaces are completely separate so anything getting through is
very unusual.

Dave.
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