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

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Message-ID: <20201123152146.GE11033@willie-the-truck>
Date:   Mon, 23 Nov 2020 15:21:47 +0000
From:   Will Deacon <will@...nel.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Rob Clark <robdclark@...il.com>,
        Akhil P Oommen <akhilpo@...eaurora.org>,
        freedreno@...ts.freedesktop.org,
        "Kristian H . Kristensen" <hoegsberg@...gle.com>,
        dri-devel@...ts.freedesktop.org, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCHv8 0/8] System Cache support for GPU and required SMMU
 support

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.

Will