linux-kernel - Re: [PATCH] iommu/arm: fix ARM_SMMU

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Date:   Wed, 13 Oct 2021 17:20:24 +0100
From:   Will Deacon <will@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Joerg Roedel <joro@...tes.org>, Arnd Bergmann <arnd@...db.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Robin Murphy <robin.murphy@....com>,
        Yong Wu <yong.wu@...iatek.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Alex Elder <elder@...aro.org>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iommu/arm: fix ARM_SMMU_QCOM compilation

Hi Arnd,

On Wed, Oct 13, 2021 at 10:33:55AM +0200, Arnd Bergmann wrote:
> On Wed, Oct 13, 2021 at 9:58 AM Will Deacon <will@...nel.org> wrote:
> > On Tue, Oct 12, 2021 at 05:18:00PM +0200, Arnd Bergmann wrote:
> > > From: Arnd Bergmann <arnd@...db.de>
> > >
> > > My previous bugfix ended up making things worse for the QCOM IOMMU
> > > driver when it forgot to add the Kconfig symbol that is getting used to
> > > control the compilation of the SMMU implementation specific code
> > > for Qualcomm.
> > >
> > > Fixes: 424953cf3c66 ("qcom_scm: hide Kconfig symbol")
> > > Reported-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> > > Reported-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > > Reported-by: John Stultz <john.stultz@...aro.org>
> > > Link: https://lore.kernel.org/lkml/20211010023350.978638-1-dmitry.baryshkov@linaro.org/
> > > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > > ---
> > > In case we want fix it this way after all, here is the patch
> > > I made. Either this one or Dmitry patch from the link above
> > > is required for v5.15
> > > ---
> > >  drivers/iommu/Kconfig | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > >
> > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > index c5c71b7ab7e8..3eb68fa1b8cc 100644
> > > --- a/drivers/iommu/Kconfig
> > > +++ b/drivers/iommu/Kconfig
> > > @@ -355,6 +355,14 @@ config ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT
> > >         'arm-smmu.disable_bypass' will continue to override this
> > >         config.
> > >
> > > +config ARM_SMMU_QCOM
> > > +     def_tristate y
> > > +     depends on ARM_SMMU && ARCH_QCOM
> > > +     select QCOM_SCM
> > > +     help
> > > +       When running on a Qualcomm platform that has the custom variant
> > > +       of the ARM SMMU, this needs to be built into the SMMU driver.
> > > +
> >
> > FWIW, I prefer this solution over changing the driver code, so:
> >
> > Acked-by: Will Deacon <will@...nel.org>
> >
> > I assume you'll be getting this fixed for 5.15?
> 
> I was hoping you and Joerg could just pick your preferred patch
> into the iommu fixes tree for v5.15.
> 
> I currently have nothing else pending for my asm-generic tree that
> introduced the regression, but I can take it through there if that helps
> you.

I also don't have any fixes pending, and I don't see any in Joerg's tree so
it's probably quickest if you send it on yourself. Is that ok?

Cheers,

Will