linux-kernel - Re: [PATCH 1/4] iommu/exynos: Set correct dma mask for SysMMU v5+

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Message-ID: <CAPLW+4kfrHOb8utzynhB=2KLDQu-NC08UYpAVjpg__NQSeSQyg@mail.gmail.com>
Date:   Fri, 8 Jul 2022 16:18:32 +0300
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        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 1/4] iommu/exynos: Set correct dma mask for SysMMU v5+

On Sun, 3 Jul 2022 at 21:50, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 02/07/2022 23:37, Sam Protsenko wrote:
> > SysMMU v5+ supports 36 bit physical address space. Set corresponding DMA
> > mask to avoid falling back to SWTLBIO usage in dma_map_single() because
> > of failed dma_capable() check.
> >
> > The original code for this fix was suggested by Marek.
> >
> > Originally-by: Marek Szyprowski <m.szyprowski@...sung.com>
>
> This is some tip specific tag, I don't think checkpatch allows it.
> Either use suggesgted-by or co-developed-by + SoB.
>

Yes, checkpatch is swearing at that line, though I encountered that
tag mentioning somewhere in Documentation. Will rework it in v2.

> > Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> > ---
> >  drivers/iommu/exynos-iommu.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
> > index 71f2018e23fe..28f8c8d93aa3 100644
> > --- a/drivers/iommu/exynos-iommu.c
> > +++ b/drivers/iommu/exynos-iommu.c
> > @@ -647,6 +647,14 @@ static int exynos_sysmmu_probe(struct platform_device *pdev)
> >               }
> >       }
> >
> > +     if (MMU_MAJ_VER(data->version) >= 5) {
> > +             ret = dma_set_mask(dev, DMA_BIT_MASK(36));
> > +             if (ret) {
> > +                     dev_err(dev, "Unable to set DMA mask: %d\n", ret);
>
> Missing cleanup: iommu_device_unregister
> and probably also: iommu_device_sysfs_remove
>

Right. Also the correct cleanup should be added for failing
iommu_device_register() case, above of the quoted code. Will do that
in v2, thanks.

Another thing is that "remove" method is missing. But guess I'll get
to it later, when adding modularization support for this driver.

> > +                     return ret;
> > +             }
> > +     }
> > +
> >       /*
> >        * use the first registered sysmmu device for performing
> >        * dma mapping operations on iommu page tables (cpu cache flush)
>
>
> Best regards,
> Krzysztof