linux-kernel - Re: [PATCH v5 0/3] drm/nouveau: set DMA mask before mapping scratch page

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Message-ID: <CAAVeFuKJ-Qmdnz1kmDtqo+P6m+aGW+DzVDkVTn+9ZLP94zO5dw@mail.gmail.com>
Date:   Fri, 7 Oct 2016 17:12:28 +0900
From:   Alexandre Courbot <gnurou@...il.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        Ben Skeggs <bskeggs@...hat.com>
Subject: Re: [PATCH v5 0/3] drm/nouveau: set DMA mask before mapping scratch page

On Fri, Oct 7, 2016 at 12:49 AM, Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
> This v4 is now a 3 piece series (since v4), after Alexandre pointed out that
> both GF 100 and NV50 are affected by the same issue, and that a related issue
> has been solved already for Tegra in commit 9d0394c6bed5
> ("drm/nouveau/instmem/gk20a: set DMA mask early").
>
> The issue that this series addresses is the fact that the Nouveau driver
> invokes the DMA API before setting the DMA mask. In both cases addressed
> here, these are simply static bidirectional mappings of scratch pages whose
> purpose is not well understood, and in most cases, it does not matter that
> these pages are always allocated below 4 GB even if the hardware can access
> memory much higher up.
>
> However, on platforms without any RAM below 4 GB, the preliminary DMA mask
> of 32 is preventing the nouveau driver from loading on GF100 and NV50
> hardware with an error like the following one:
>
>    nouveau 0000:02:00.0: enabling device (0000 -> 0003)
>    nouveau 0000:02:00.0: NVIDIA GT218 (0a8280b1)
>    nouveau 0000:02:00.0: bios: version 70.18.a6.00.00
>    nouveau 0000:02:00.0: fb ctor failed, -14
>    nouveau: probe of 0000:02:00.0 failed with error -14
>
> So fix this by setting a preliminary DMA mask based on the MMU device 'dma_bits'
> property (patch #1), and postpone mapping the scratch pages to the respective
> FB .init() hooks. (#2 and #3)
>
> v5: move setting of preliminary DMA mask to nvkm_device_pci_new() (#1)
>     move allocation and DMA mapping of scratch pages to .oneinit hooks (#2, #3)
> v4: split and move dma_set_mask to probe hook (Alexander)
> v3: rework code to get rid of DMA_ERROR_CODE references, which is not
>     defined on all architectures
> v2: replace incorrect comparison of dma_addr_t type var against NULL
>
> Ard Biesheuvel (3):
>   drm/nouveau: set streaming DMA mask early
>   drm/nouveau/fb/gf100: defer DMA mapping of scratch page to oneinit()
>     hook
>   drm/nouveau/fb/nv50: defer DMA mapping of scratch page to oneinit()
>     hook

The series,

Reviewed-by: Alexandre Courbot <acourbot@...dia.com>

Thanks!