linux-kernel - Re: [PATCH] iommu: fix ARM_SMMU vs QCOM

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Date:   Sat, 9 Oct 2021 23:16:38 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Arnd Bergmann <arnd@...db.de>,
        Thierry Reding <treding@...dia.com>,
        Andy Gross <agross@...nel.org>, linux-arm-msm@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH] iommu: fix ARM_SMMU vs QCOM_SCM compilation

On Sat 09 Oct 21:33 CDT 2021, Dmitry Baryshkov wrote:

> After commit 424953cf3c66 ("qcom_scm: hide Kconfig symbol") arm-smmu got
> qcom_smmu_impl_init() call guarded by IS_ENABLED(CONFIG_ARM_SMMU_QCOM).
> However the CONFIG_ARM_SMMU_QCOM Kconfig entry does not exist, so the
> qcom_smmu_impl_init() is never called.
> 
> So, let's fix this by always calling qcom_smmu_impl_init(). It does not
> touch the smmu passed unless the device is a non-Qualcomm one. Make
> ARM_SMMU select QCOM_SCM for ARCH_QCOM.
> 

Arnd's intention was to not force QCOM_SCM to be built on non-Qualcomm
devices. But as Daniel experienced, attempting to boot most Qualcomm
boards without this results in a instant reboot.

I think it's okay if we tinker with CONFIG_ARM_SMMU_QCOM for v5.16, but
we're getting late in v5.15 so I would prefer if we make sure this works
out of the box.

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Regards,
Bjorn

> Fixes: 424953cf3c66 ("qcom_scm: hide Kconfig symbol")
> Cc: Arnd Bergmann <arnd@...db.de>
> Reported-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>  drivers/iommu/Kconfig                      | 1 +
>  drivers/iommu/arm/arm-smmu/Makefile        | 3 +--
>  drivers/iommu/arm/arm-smmu/arm-smmu-impl.c | 9 +++++++--
>  3 files changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index c5c71b7ab7e8..a4593e53fe7d 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -309,6 +309,7 @@ config ARM_SMMU
>  	tristate "ARM Ltd. System MMU (SMMU) Support"
>  	depends on ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)
>  	select IOMMU_API
> +	select QCOM_SCM
>  	select IOMMU_IO_PGTABLE_LPAE
>  	select ARM_DMA_USE_IOMMU if ARM
>  	help
> diff --git a/drivers/iommu/arm/arm-smmu/Makefile b/drivers/iommu/arm/arm-smmu/Makefile
> index b0cc01aa20c9..e240a7bcf310 100644
> --- a/drivers/iommu/arm/arm-smmu/Makefile
> +++ b/drivers/iommu/arm/arm-smmu/Makefile
> @@ -1,5 +1,4 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
>  obj-$(CONFIG_ARM_SMMU) += arm_smmu.o
> -arm_smmu-objs += arm-smmu.o arm-smmu-impl.o arm-smmu-nvidia.o
> -arm_smmu-$(CONFIG_ARM_SMMU_QCOM) += arm-smmu-qcom.o
> +arm_smmu-objs += arm-smmu.o arm-smmu-impl.o arm-smmu-nvidia.o arm-smmu-qcom.o
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-impl.c b/drivers/iommu/arm/arm-smmu/arm-smmu-impl.c
> index 2c25cce38060..8199185dd262 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-impl.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-impl.c
> @@ -215,8 +215,13 @@ struct arm_smmu_device *arm_smmu_impl_init(struct arm_smmu_device *smmu)
>  	    of_device_is_compatible(np, "nvidia,tegra186-smmu"))
>  		return nvidia_smmu_impl_init(smmu);
>  
> -	if (IS_ENABLED(CONFIG_ARM_SMMU_QCOM))
> -		smmu = qcom_smmu_impl_init(smmu);
> +	/*
> +	 * qcom_smmu_impl_init() will not touch smmu if the device is not
> +	 * a Qualcomm one.
> +	 */
> +	smmu = qcom_smmu_impl_init(smmu);
> +	if (IS_ERR(smmu))
> +		return smmu;
>  
>  	if (of_device_is_compatible(np, "marvell,ap806-smmu-500"))
>  		smmu->impl = &mrvl_mmu500_impl;
> -- 
> 2.30.2
>