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[104.57.184.186]) by smtp.gmail.com with ESMTPSA id m66sm2805314oia.28.2021.05.25.10.14.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 May 2021 10:14:47 -0700 (PDT) Date: Tue, 25 May 2021 12:14:45 -0500 From: Bjorn Andersson To: Will Deacon Cc: Rob Clark , Eric Anholt , dri-devel , linux-arm-msm , freedreno , Sean Paul , Jordan Crouse , Robin Murphy , Rob Herring , Joerg Roedel , "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Linux Kernel Mailing List Subject: Re: [PATCH 1/2] iommu/arm-smmu-qcom: Skip the TTBR1 quirk for db820c. Message-ID: References: <20210326231303.3071950-1-eric@anholt.net> <20210329144729.GB4203@willie-the-truck> <20210330093432.GB5281@willie-the-truck> <20210330153050.GB6567@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210330153050.GB6567@willie-the-truck> Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Tue 30 Mar 10:31 CDT 2021, Will Deacon wrote: > On Tue, Mar 30, 2021 at 08:03:36AM -0700, Rob Clark wrote: > > On Tue, Mar 30, 2021 at 2:34 AM Will Deacon wrote: > > > > > > On Mon, Mar 29, 2021 at 09:02:50PM -0700, Rob Clark wrote: > > > > On Mon, Mar 29, 2021 at 7:47 AM Will Deacon 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. > > > > Just a driver issue (and the fact that currently we don't have > > physical access to a device... debugging a5xx per-process-pgtables by > > pushing untested things to the CI farm is kind of a difficult way to > > work) > > But then in that case, this is using the compatible string to identify a > driver issue, no? > No the compatible addition identifies the hardware, the implementation then uses this information to know that it needs to behave "differently" on this platform. When/if someone decides to add the necessary support in the driver they can remove the driver quirk, but it doesn't invalidate the specific compatible. Regards, Bjorn