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

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Message-ID: <87a8ic44cg.fsf@e105922-lin.cambridge.arm.com>
Date:	Thu, 23 Jun 2016 10:55:11 +0100
From:	Punit Agrawal <punit.agrawal@....com>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	bskeggs@...hat.com, airlied@...ux.ie, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] drm/nouveau/fb/nv50: set DMA mask before mapping scratch page

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.

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

Cheers,
Punit


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