linux-kernel - Re: [RFC PATCH] drm/nouveau/fb/nv50: set DMA mask before mapping scratch page

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Date:	Thu, 23 Jun 2016 12:07:58 +0200
From:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:	Punit Agrawal <punit.agrawal@....com>
Cc:	nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	bskeggs@...hat.com, airlied@...ux.ie,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] drm/nouveau/fb/nv50: set DMA mask before mapping
 scratch page

On 23 June 2016 at 11:55, Punit Agrawal <punit.agrawal@....com> wrote:
> Ard Biesheuvel <ard.biesheuvel@...aro.org> writes:
>
>> The 100c08 scratch page is mapped using dma_map_page() before the TTM
>> layer has had a chance to set the DMA mask. This means we are still
>> running with the default of 32 when this code executes, and this causes
>> problems for platforms with no memory below 4 GB (such as AMD Seattle)
>>
>> So move the dma_map_page() to the .init hook, and set the streaming DMA
>> mask based on the MMU subdev parameters before performing the call.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>
> Hi Ard,
>
> Thanks for posting this patch.
>
> With the patch, I am able to see console output on a screen attached to
> the NVS 300 PCIe card in an AMD Seattle system. It was failing with
> a message similar to what you've posted below.
>

Thanks for the report. May I take it as a tested-by?

> For some reason, X refuses to start up but that, I think, is a problem
> with my userspace setup.
>

Good to know that you are attempting the same thing. We should take
this offline, but I'd like to compare notes regarding the Xorg
problems that you are experiencing.

Regards,
Ard.