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

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Date:   Fri, 1 Nov 2019 17:25:08 +0000
From:   Will Deacon <will@...nel.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.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 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)

Will