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

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Date:   Wed, 13 Oct 2021 08:58:03 +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>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/arm: fix ARM_SMMU_QCOM compilation

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?

Cheers,

Will