linux-kernel - Re: [PATCH 0/4] iommu/exynos: Add basic support for SysMMU v7

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Message-ID: <CAPLW+4k9DBbX6PupEk-J_KFbLmwgbfuDrfuVgyapT=d4WMG7yQ@mail.gmail.com>
Date:   Wed, 6 Jul 2022 17:24:43 +0300
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Janghyuck Kim <janghyuck.kim@...sung.com>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        David Virag <virag.david003@...il.com>,
        Cho KyongHo <pullip.cho@...sung.com>,
        Daniel Mentz <danielmentz@...gle.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        iommu@...ts.linux-foundation.org, iommu@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] iommu/exynos: Add basic support for SysMMU v7

On Sun, 3 Jul 2022 at 13:47, David Virag <virag.david003@...il.com> wrote:
>
> On Sun, 2022-07-03 at 00:48 +0300, Sam Protsenko wrote:
> [...]
> > Hi Marek,
> >
> > As I understand, you have some board with SysMMU v7, which is not VM
> > capable (judging from the patches you shared earlier). Could you
> > please somehow verify if this series works fine for you? For example,
> > this testing driver [1] can be helpful.
> >
> > Thanks!
> >
> > [1]
> > https://github.com/joe-skb7/linux/commit/bbadd46fa525fe1fef2ccbdfff81f7d29caf0506
>
> Hi Sam,
>
> Not Marek here, but I wanted to try this on my jackpotlte (Exynos
> 7885). The driver reports it's DPU sysmmu as version 7.2, and manually
> reading the capabilities registers it looks like it has the 2nd
> capability register but not the VM capability.
>
> After applying your patches, adding your test driver (with SYSMMU_BASE
> corrected to 7885 value), and adding the sysmmu to dt, I tried to cat
> the test file that it creates in debugfs and I got an SError kernel
> panic.
>
> I tried tracing where the SError happens and it looks like it's this
> line:
>         /* Preload for emulation */
>         iowrite32(rw | vpn, obj->reg_base + MMU_EMU_PRELOAD);
>
> Trying to read the EMU registers using devmem results in a "Bus error".
>
> Could these emulation registers be missing from my SysMMU? Do you have
> any info on what version should have it? Or maybe some capability bit?
> I'll try testing it with DECON/DPP later and see if it works that way.
>

Hi Janghyuck,

Do you have by chance any info on SysMMU v7.2, which is present e.g.
on Exynos7885? David is trying to use emulation registers there with
no luck, so it would be nice if you can provide some details on
questions above.

Thanks!

> Best regards,
> David