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From: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
To: Rob Clark <robdclark@gmail.com>
Cc: Will Deacon <will@kernel.org>, David Airlie <airlied@linux.ie>,
	Sean Paul <sean@poorly.run>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Akhil P Oommen <akhilpo@codeaurora.org>,
	Emil Velikov <emil.velikov@collabora.com>,
	"list@263.net:IOMMU DRIVERS , Joerg Roedel <joro@8bytes.org>,
	" <iommu@lists.linux-foundation.org>,
	Matthias Kaehlcke <mka@chromium.org>,
	"Kristian H . Kristensen" <hoegsberg@google.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Stephen Boyd <swboyd@chromium.org>,
	freedreno <freedreno@lists.freedesktop.org>,
	Sharat Masetty <smasetty@codeaurora.org>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
	<linux-arm-kernel@lists.infradead.org>,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCHv3 7/7] drm/msm/a6xx: Add support for using system cache(LLC)
Date: Fri, 03 Jul 2020 22:29:16 +0530	[thread overview]
Message-ID: <c925406446bb2f6c7aead8e047672cae@codeaurora.org> (raw)
In-Reply-To: <CAF6AEGsCROVTsi2R7_aUkmH9Luoc_guMR0w0KUJc2cEgpfj79w@mail.gmail.com>

On 2020-07-03 21:34, Rob Clark wrote:
> 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
> 

Ok then we are good to remove unused sys cache prot flag which Will has 
posted.

Thanks,
Sai

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  reply	other threads:[~2020-07-03 16:59 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
2020-07-03 16:59         ` Sai Prakash Ranjan [this message]
2020-07-09 16:13         ` Jordan Crouse

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