linux-kernel - Re: [PATCH v3 3/4] iommu/arm-smmu: Add support to handle Qcom's wait-for-safe logic

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Message-ID: <CAFp+6iH-KzX7x1j8AAuKJcOP6v=fyP-yLvaeeE_Ly3oueu_ngg@mail.gmail.com>
Date:   Wed, 26 Jun 2019 12:03:02 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Will Deacon <will@...nel.org>
Cc:     "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Will Deacon <will.deacon@....com>,
        open list <linux-kernel@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        David Brown <david.brown@...aro.org>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        "robh+dt" <robh+dt@...nel.org>, Andy Gross <agross@...nel.org>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH v3 3/4] iommu/arm-smmu: Add support to handle Qcom's
 wait-for-safe logic

On Tue, Jun 25, 2019 at 7:09 PM Will Deacon <will@...nel.org> wrote:
>
> On Tue, Jun 25, 2019 at 12:34:56PM +0530, Vivek Gautam wrote:
> > On Mon, Jun 24, 2019 at 10:33 PM Will Deacon <will@...nel.org> wrote:
> > > Instead, I think this needs to be part of a separate file that is maintained
> > > by you, which follows on from the work that Krishna is doing for nvidia
> > > built on top of Robin's prototype patches:
> > >
> > > http://linux-arm.org/git?p=linux-rm.git;a=shortlog;h=refs/heads/iommu/smmu-impl
> >
> > Looking at this branch quickly, it seem there can be separate implementation
> > level configuration file that can be added.
> > But will this also handle separate page table ops when required in future.
>
> Nothing's set in stone, but having the implementation-specific code
> constrain the page-table format (especially wrt quirks) sounds reasonable to
> me. I'm currently waiting for Krishna to respin the nvidia changes [1] on
> top of this so that we can see how well the abstractions are holding up.

Sure. Would you want me to try Robin's branch and take out the qualcomm
related stuff to its own implementation? Or, would you like me to respin this
series so that you can take it in to enable SDM845 boards such as, MTP
and dragonboard to have a sane build - debian, etc. so people benefit
out of it.
Qualcomm stuff is lying in qcom-smmu and arm-smmu and may take some
time to stub out the implementation related details.
Let me know your take.

Thanks & regards
Vivek

>
> I certainly won't merge the stuff until we have a user.
>
> Will
>
> [1] https://lkml.kernel.org/r/1543887414-18209-1-git-send-email-vdumpa@nvidia.com
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

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