linux-kernel - Re: [PATCHv8 0/8] System Cache support for GPU and required SMMU support

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Date:   Mon, 23 Nov 2020 11:22:31 -0800
From:   Rob Clark <robdclark@...il.com>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Akhil P Oommen <akhilpo@...eaurora.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        "Kristian H . Kristensen" <hoegsberg@...gle.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCHv8 0/8] System Cache support for GPU and required SMMU support

On Mon, Nov 23, 2020 at 9:01 AM Sai Prakash Ranjan
<saiprakash.ranjan@...eaurora.org> wrote:
>
> On 2020-11-23 20:51, Will Deacon wrote:
> > On Tue, Nov 17, 2020 at 08:00:39PM +0530, Sai Prakash Ranjan wrote:
> >> Some hardware variants contain a system cache or the last level
> >> cache(llc). This cache is typically a large block which is shared
> >> by multiple clients on the SOC. GPU uses the system cache to cache
> >> both the GPU data buffers(like textures) as well the SMMU pagetables.
> >> This helps with improved render performance as well as lower power
> >> consumption by reducing the bus traffic to the system memory.
> >>
> >> The system cache architecture allows the cache to be split into slices
> >> which then be used by multiple SOC clients. This patch series is an
> >> effort to enable and use two of those slices preallocated for the GPU,
> >> one for the GPU data buffers and another for the GPU SMMU hardware
> >> pagetables.
> >>
> >> Patch 1 - Patch 6 adds system cache support in SMMU and GPU driver.
> >> Patch 7 and 8 are minor cleanups for arm-smmu impl.
> >>
> >> Changes in v8:
> >>  * Introduce a generic domain attribute for pagetable config (Will)
> >>  * Rename quirk to more generic IO_PGTABLE_QUIRK_ARM_OUTER_WBWA (Will)
> >>  * Move non-strict mode to use new struct domain_attr_io_pgtbl_config
> >> (Will)
> >
> > Modulo some minor comments I've made, this looks good to me. What is
> > the
> > plan for merging it? I can take the IOMMU parts, but patches 4-6 touch
> > the
> > MSM GPU driver and I'd like to avoid conflicts with that.
> >
>
> SMMU bits are pretty much independent and GPU relies on the domain
> attribute
> and the quirk exposed, so as long as SMMU changes go in first it should
> be good.
> Rob?

I suppose one option would be to split out the patch that adds the
attribute into it's own patch, and merge that both thru drm and iommu?

If Will/Robin dislike that approach, I'll pick up the parts of the drm
patches which don't depend on the new attribute for v5.11 and the rest
for v5.12.. or possibly a second late v5.11 pull req if airlied
doesn't hate me too much for it.

Going forward, I think we will have one or two more co-dependent
series, like the smmu iova fault handler improvements that Jordan
posted.  So I would like to hear how Will and Robin prefer to handle
those.

BR,
-R


> Thanks,
> Sai
>
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
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