linux-kernel - Re: [PATCH] ALSA: hda - allow 40 bit DMA mask for NVidia devices

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Message-ID: <CAKv+Gu_CVwb_Vbaj1j55c3nERzv6YR=STjJTqE7+v2T+Kh4RnA@mail.gmail.com>
Date:   Tue, 18 Oct 2016 11:26:42 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     alsa-devel@...a-project.org, perex@...ex.cz,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mike Travis <travis@....com>
Subject: Re: [PATCH] ALSA: hda - allow 40 bit DMA mask for NVidia devices

On 18 October 2016 at 11:25, Takashi Iwai <tiwai@...e.de> wrote:
> On Mon, 17 Oct 2016 18:23:59 +0200,
> Ard Biesheuvel wrote:
>>
>> Commit 49d9e77e72cf ("ALSA: hda - Fix system panic when DMA > 40 bits
>> for Nvidia audio controllers") simply disabled any DMA exceeding 32
>> bits for NVidia devices, even though they are capable of performing
>> DMA up to 40 bits. On some architectures (such as arm64), system memory
>> is not guaranteed to be 32-bit addressable by PCI devices, and so this
>> change prevents NVidia devices from working on platforms such as AMD
>> Seattle.
>>
>> Since the original commit already mentioned that up to 40 bits of DMA
>> is supported, and given that the code has been updated in the meantime
>> to support a 40 bit DMA mask on other devices, revert commit 49d9e77e72cf
>> and explicitly set the DMA mask to 40 bits for NVidia devices.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>
> Thanks, applied.  Since this seems causing a real problem, I added Cc
> to stable.
>

Thanks!