linux-kernel - Re: [PATCH v3 1/1] drm: msm: Replace dma_map_sg with dma_sync

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Message-ID: <20181129155418.GB26537@lst.de>
Date:   Thu, 29 Nov 2018 16:54:18 +0100
From:   Christoph Hellwig <hch@....de>
To:     Rob Clark <robdclark@...il.com>
Cc:     hch@....de, Vivek Gautam <vivek.gautam@...eaurora.org>,
        David Airlie <airlied@...ux.ie>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Archit Taneja <architt@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Sean Paul <seanpaul@...omium.org>
Subject: Re: [PATCH v3 1/1] drm: msm: Replace dma_map_sg with dma_sync_sg*

On Thu, Nov 29, 2018 at 09:42:50AM -0500, Rob Clark wrote:
> Maybe the thing we need to do is just implement a blacklist of
> compatible strings for devices which should skip the automatic
> iommu/dma hookup.  Maybe a bit ugly, but it would also solve a problem
> preventing us from enabling per-process pagetables for a5xx (where we
> need to control the domain/context-bank that is allocated by the dma
> api).

You can detach from the dma map attachment using arm_iommu_detach_device,
which a few drm drivers do, but I don't think this is the problem.