linux-kernel - Re: [PATCHv7 0/3] QCOM smmu-500 wait-for-safe handling for sdm845

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Date:   Fri, 01 Nov 2019 22:49:00 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Will Deacon <will@...nel.org>
Cc:     agross@...nel.org, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org,
        Stephen Boyd <swboyd@...omium.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        bjorn.andersson@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCHv7 0/3] QCOM smmu-500 wait-for-safe handling for sdm845

On 2019-11-01 22:01, Will Deacon wrote:
> On Fri, Sep 20, 2019 at 01:34:26PM +0530, Sai Prakash Ranjan wrote:
>> Previous version of the patches are at [1]:
>> 
>> QCOM's implementation of smmu-500 on sdm845 adds a hardware logic 
>> called
>> wait-for-safe. This logic helps in meeting the invalidation 
>> requirements
>> from 'real-time clients', such as display and camera. This 
>> wait-for-safe
>> logic ensures that the invalidations happen after getting an ack from 
>> these
>> devices.
>> In this patch-series we are disabling this wait-for-safe logic from 
>> the
>> arm-smmu driver's probe as with this enabled the hardware tries to
>> throttle invalidations from 'non-real-time clients', such as USB and 
>> UFS.
>> 
>> For detailed information please refer to patch [3/4] in this series.
>> I have included the device tree patch too in this series for someone 
>> who
>> would like to test out this. Here's a branch [2] that gets display on 
>> MTP
>> SDM845 device.
>> 
>> This patch series is inspired from downstream work to handle 
>> under-performance
>> issues on real-time clients on sdm845. In downstream we add separate 
>> page table
>> ops to handle TLB maintenance and toggle wait-for-safe in tlb_sync 
>> call so that
>> achieve required performance for display and camera [3, 4].
> 
> What's the plan for getting this merged? I'm not happy taking the 
> firmware
> bits without Andy's ack, but I also think the SMMU changes should go 
> via
> the IOMMU tree to avoid conflicts.
> 
> Andy?
> 

Bjorn maintains QCOM stuff now if I am not wrong and he has already 
reviewed the firmware bits. So I'm hoping you could take all these 
through IOMMU tree.

-Sai

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