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

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Message-ID: <119d4bcf5989d1aa0686fd674c6a3370@codeaurora.org>
Date:   Fri, 01 Nov 2019 23:01:59 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Will Deacon <will@...nel.org>, bjorn.andersson@...aro.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 22:55, Will Deacon wrote:
> On Fri, Nov 01, 2019 at 10:49:00PM +0530, Sai Prakash Ranjan wrote:
>> 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.
> 
> Oh, I didn't realise that. Is there a MAINTAINERS update someplace? If 
> I
> run:
> 
> $ ./scripts/get_maintainer.pl -f drivers/firmware/qcom_scm-64.c
> 
> in linux-next, I get:
> 
> Andy Gross <agross@...nel.org> (maintainer:ARM/QUALCOMM SUPPORT)
> linux-arm-msm@...r.kernel.org (open list:ARM/QUALCOMM SUPPORT)
> linux-kernel@...r.kernel.org (open list)
> 

It hasn't been updated yet then. I will leave it to Bjorn or Andy to 
comment on this.

-Sai

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