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From:   Rob Clark <robdclark@gmail.com>
Date:   Wed, 5 Jun 2019 07:16:51 -0700
Message-ID: <CAF6AEGtb1t4oRXCVvZq_cq1vZCJhgok-Ha+FXrruOOCq4APY_Q@mail.gmail.com>
Subject: Re: [Freedreno] [PATCH] of/device: add blacklist for iommu dma_ops
To:     Marek Szyprowski <m.szyprowski@samsung.com>
Cc:     Tomasz Figa <tfiga@chromium.org>,
        freedreno <freedreno@lists.freedesktop.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        Frank Rowand <frowand.list@gmail.com>,
        devicetree@vger.kernel.org, David Airlie <airlied@linux.ie>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Will Deacon <will.deacon@arm.com>,
        Doug Anderson <dianders@chromium.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux IOMMU <iommu@lists.linux-foundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Sean Paul <seanpaul@chromium.org>,
        Vivek Gautam <vivek.gautam@codeaurora.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Christoph Hellwig <hch@lst.de>
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On Wed, Jun 5, 2019 at 6:18 AM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
>
> Hi Rob,
>
> On 2019-06-05 14:57, Rob Clark wrote:
> > On Tue, Jun 4, 2019 at 11:58 PM Tomasz Figa <tfiga@chromium.org> wrote:
> >> But first of all, I remember Marek already submitted some patches long
> >> ago that extended struct driver with some flag that means that the
> >> driver doesn't want the IOMMU to be attached before probe. Why
> >> wouldn't that work? Sounds like a perfect opt-out solution.
> > Actually, yeah.. we should do that.  That is the simplest solution.
>
> Tomasz has very good memory. It took me a while to find that old patches:
>
> https://patchwork.kernel.org/patch/4677251/
> https://patchwork.kernel.org/patch/4677941/
> https://patchwork.kernel.org/patch/4677401/
>
> It looks that my idea was a bit ahead of its time ;)
>

if I re-spin this, was their a reason not to just use bitfields, ie:

-    bool suppress_bind_attrs;    /* disables bind/unbind via sysfs */
+    bool suppress_bind_attrs : 1;    /* disables bind/unbind via sysfs */
+    bool has_own_iommu_manager : 1;  /* driver explictly manages IOMMU */

That seems like it would have been a bit less churn and a bit nicer
looking (IMO at least)

BR,
-R