netdev - Re: [PATCH] [RFC] qcom_scm: hide Kconfig symbol

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Date:   Wed, 29 Sep 2021 09:46:27 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Joerg Roedel <joro@...tes.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Alex Elder <elder@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, ath10k@...ts.infradead.org,
        linux-wireless <linux-wireless@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH] [RFC] qcom_scm: hide Kconfig symbol

On Wed 29 Sep 05:04 CDT 2021, Arnd Bergmann wrote:

> On Wed, Sep 29, 2021 at 11:51 AM Will Deacon <will@...nel.org> wrote:
> > On Mon, Sep 27, 2021 at 05:22:13PM +0200, Arnd Bergmann wrote:
> > >
> > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > index 124c41adeca1..989c83acbfee 100644
> > > --- a/drivers/iommu/Kconfig
> > > +++ b/drivers/iommu/Kconfig
> > > @@ -308,7 +308,7 @@ config APPLE_DART
> > >  config ARM_SMMU
> > >       tristate "ARM Ltd. System MMU (SMMU) Support"
> > >       depends on ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)
> > > -     depends on QCOM_SCM || !QCOM_SCM #if QCOM_SCM=m this can't be =y
> > > +     select QCOM_SCM
> > >       select IOMMU_API
> > >       select IOMMU_IO_PGTABLE_LPAE
> > >       select ARM_DMA_USE_IOMMU if ARM
> >
> > I don't want to get in the way of this patch because I'm also tired of the
> > randconfig failures caused by QCOM_SCM. However, ARM_SMMU is applicable to
> > a wide variety of (non-qcom) SoCs and so it seems a shame to require the
> > QCOM_SCM code to be included for all of those when it's not strictly needed
> > at all.
> 
> Good point, I agree that needs to be fixed. I think this additional
> change should do the trick:
> 

ARM_SMMU and QCOM_IOMMU are two separate implementations and both uses
QCOM_SCM. So both of them should select QCOM_SCM.

"Unfortunately" the Qualcomm portion of ARM_SMMU is builtin
unconditionally, so going with something like select QCOM_SCM if
ARCH_QCOM would still require the stubs in qcom_scm.h.

Regards,
Bjorn

> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -308,7 +308,6 @@ config APPLE_DART
>  config ARM_SMMU
>         tristate "ARM Ltd. System MMU (SMMU) Support"
>         depends on ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)
> -       select QCOM_SCM
>         select IOMMU_API
>         select IOMMU_IO_PGTABLE_LPAE
>         select ARM_DMA_USE_IOMMU if ARM
> @@ -438,7 +437,7 @@ config QCOM_IOMMU
>         # Note: iommu drivers cannot (yet?) be built as modules
>         bool "Qualcomm IOMMU Support"
>         depends on ARCH_QCOM || (COMPILE_TEST && !GENERIC_ATOMIC64)
> -       depends on QCOM_SCM=y
> +       select QCOM_SCM
>         select IOMMU_API
>         select IOMMU_IO_PGTABLE_LPAE
>         select ARM_DMA_USE_IOMMU
> 
> I'll see if that causes any problems for the randconfig builds.
> 
>        Arnd