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

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Message-ID: <20201124111027.GA13151@willie-the-truck>
Date:   Tue, 24 Nov 2020 11:10:28 +0000
From:   Will Deacon <will@...nel.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Rob Clark <robdclark@...il.com>,
        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 , 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 Tue, Nov 24, 2020 at 09:32:54AM +0530, Sai Prakash Ranjan wrote:
> On 2020-11-24 00:52, Rob Clark wrote:
> > 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?
> > 
> 
> Ok I can split out domain attr and quirk into its own patch if Will is
> fine with that approach.

Why don't I just queue the first two patches on their own branch and we
both pull that?

Will