Re: [PATCH 1/2] iommu/arm-smmu-qcom: Skip the TTBR1 quirk for db820c.

From: Will Deacon <will@kernel.org>
To: Rob Clark <robdclark@gmail.com>
Cc: Eric Anholt <eric@anholt.net>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	freedreno <freedreno@lists.freedesktop.org>,
	Sean Paul <sean@poorly.run>,
	Jordan Crouse <jcrouse@codeaurora.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Rob Herring <robh+dt@kernel.org>, Joerg Roedel <joro@8bytes.org>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
	<linux-arm-kernel@lists.infradead.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] iommu/arm-smmu-qcom: Skip the TTBR1 quirk for db820c.
Date: Tue, 30 Mar 2021 10:34:33 +0100	[thread overview]
Message-ID: <20210330093432.GB5281@willie-the-truck> (raw)
In-Reply-To: <CAF6AEGugpEk396DVtWX=W+uf3p-wcgBfCSpSLWGQJE1vKpJ4aw@mail.gmail.com>

On Mon, Mar 29, 2021 at 09:02:50PM -0700, Rob Clark wrote:
> On Mon, Mar 29, 2021 at 7:47 AM Will Deacon <will@kernel.org> wrote:
> >
> > On Fri, Mar 26, 2021 at 04:13:02PM -0700, Eric Anholt wrote:
> > > db820c wants to use the qcom smmu path to get HUPCF set (which keeps
> > > the GPU from wedging and then sometimes wedging the kernel after a
> > > page fault), but it doesn't have separate pagetables support yet in
> > > drm/msm so we can't go all the way to the TTBR1 path.
> >
> > What do you mean by "doesn't have separate pagetables support yet"? The
> > compatible string doesn't feel like the right way to determine this.
> 
> the compatible string identifies what it is, not what the sw
> limitations are, so in that regard it seems right to me..

Well it depends on what "doesn't have separate pagetables support yet"
means. I can't tell if it's a hardware issue, a firmware issue or a driver
issue.

Will