From: Rob Clark <robdclark@gmail.com>
To: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc: Sean Paul <sean@poorly.run>,
freedreno <freedreno@lists.freedesktop.org>,
David Airlie <airlied@linux.ie>, Will Deacon <will@kernel.org>,
"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>,
" <iommu@lists.linux-foundation.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Matthias Kaehlcke <mka@chromium.org>,
Akhil P Oommen <akhilpo@codeaurora.org>,
Daniel Vetter <daniel@ffwll.ch>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
"Kristian H . Kristensen" <hoegsberg@google.com>,
Stephen Boyd <swboyd@chromium.org>,
Robin Murphy <robin.murphy@arm.com>,
Sharat Masetty <smasetty@codeaurora.org>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>,
Emil Velikov <emil.velikov@collabora.com>
Subject: Re: [PATCHv3 7/7] drm/msm/a6xx: Add support for using system cache(LLC)
Date: Fri, 3 Jul 2020 09:04:49 -0700 [thread overview]
Message-ID: <CAF6AEGsCROVTsi2R7_aUkmH9Luoc_guMR0w0KUJc2cEgpfj79w@mail.gmail.com> (raw)
In-Reply-To: <ecfda7ca80f6d7b4ff3d89b8758f4dc9@codeaurora.org>
On Fri, Jul 3, 2020 at 7:53 AM Sai Prakash Ranjan
<saiprakash.ranjan@codeaurora.org> wrote:
>
> Hi Will,
>
> On 2020-07-03 19:07, Will Deacon wrote:
> > On Mon, Jun 29, 2020 at 09:22:50PM +0530, Sai Prakash Ranjan wrote:
> >> diff --git a/drivers/gpu/drm/msm/msm_iommu.c
> >> b/drivers/gpu/drm/msm/msm_iommu.c
> >> index f455c597f76d..bd1d58229cc2 100644
> >> --- a/drivers/gpu/drm/msm/msm_iommu.c
> >> +++ b/drivers/gpu/drm/msm/msm_iommu.c
> >> @@ -218,6 +218,9 @@ static int msm_iommu_map(struct msm_mmu *mmu,
> >> uint64_t iova,
> >> iova |= GENMASK_ULL(63, 49);
> >>
> >>
> >> + if (mmu->features & MMU_FEATURE_USE_SYSTEM_CACHE)
> >> + prot |= IOMMU_SYS_CACHE_ONLY;
> >
> > Given that I think this is the only user of IOMMU_SYS_CACHE_ONLY, then
> > it
> > looks like it should actually be a property on the domain because we
> > never
> > need to configure it on a per-mapping basis within a domain, and
> > therefore
> > it shouldn't be exposed by the IOMMU API as a prot flag.
> >
> > Do you agree?
> >
>
> GPU being the only user is for now, but there are other clients which
> can use this.
> Plus how do we set the memory attributes if we do not expose this as
> prot flag?
It does appear that the downstream kgsl driver sets this for basically
all mappings.. well there is some conditional stuff around
DOMAIN_ATTR_USE_LLC_NWA but it seems based on the property of the
domain. (Jordan may know more about what that is about.) But looks
like there are a lot of different paths into iommu_map in kgsl so I
might have missed something.
Assuming there isn't some case where we specifically don't want to use
the system cache for some mapping, I think it could be a domain
attribute that sets an io_pgtable_cfg::quirks flag
BR,
-R
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next prev parent reply other threads:[~2020-07-03 16:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-29 15:52 [PATCHv3 0/7] System Cache support for GPU and required SMMU support Sai Prakash Ranjan
2020-06-29 15:52 ` [PATCHv3 1/7] iommu/arm-smmu: Add a init_context_bank implementation hook Sai Prakash Ranjan
2020-06-29 15:52 ` [PATCHv3 2/7] iommu/io-pgtable-arm: Add support to use system cache Sai Prakash Ranjan
2020-06-29 15:52 ` [PATCHv3 3/7] iommu/arm-smmu: Add domain attribute for " Sai Prakash Ranjan
2020-06-29 15:52 ` [PATCHv3 4/7] iommu: arm-smmu-impl: Remove unwanted extra blank lines Sai Prakash Ranjan
2020-06-29 15:52 ` [PATCHv3 5/7] iommu: arm-smmu-impl: Convert to use of_match_node() for qcom impl Sai Prakash Ranjan
2020-06-29 15:52 ` [PATCHv3 6/7] drm/msm: rearrange the gpu_rmw() function Sai Prakash Ranjan
2020-06-29 15:52 ` [PATCHv3 7/7] drm/msm/a6xx: Add support for using system cache(LLC) Sai Prakash Ranjan
2020-07-03 13:37 ` Will Deacon
2020-07-03 14:53 ` Sai Prakash Ranjan
2020-07-03 15:40 ` Will Deacon
2020-07-03 16:04 ` Rob Clark [this message]
2020-07-03 16:59 ` Sai Prakash Ranjan
2020-07-09 16:13 ` Jordan Crouse
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