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

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Message-ID: <CAPLW+4=pikbLQZLabv7aZvGhA_30xaJRYLxK+uOUUXnwu2Byow@mail.gmail.com>
Date:   Wed, 13 Jul 2022 17:14:46 +0300
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     David Virag <virag.david003@...il.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>,
        Janghyuck Kim <janghyuck.kim@...sung.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.
>

Hey David,

Can you please try out the [1] branch again? I've added support for
Exynos7885 there, using the info provided by Janghyuck Kim: apparently
Exynos7885 has EMU registers, but those have some other offsets than
on Exynos850:

    #define MMU_EMU_PRELOAD    0x8040
    #define MMU_EMU_SHOT       0x8044

I wonder if my changes to [1] do the trick.

[1] https://github.com/joe-skb7/linux/tree/e850-96-mainline-iommu

> Best regards,
> David