linux-kernel - Re: [PATCH] iommu/arm-smmu: support SMMU module probing from the IORT

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Message-ID: <20191125160445.GA24078@e121166-lin.cambridge.arm.com>
Date:   Mon, 25 Nov 2019 16:04:52 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     will@...nel.org, bhelgaas@...gle.com, gregkh@...uxfoundation.org,
        iommu@...ts.linuxfoundation.org, isaacm@...eaurora.org,
        jcrouse@...eaurora.org, jean-philippe@...aro.org,
        john.garry@...wei.com, joro@...tes.org,
        linux-kernel@...r.kernel.org, robin.murphy@....com,
        saravanak@...gle.com
Subject: Re: [PATCH] iommu/arm-smmu: support SMMU module probing from the IORT

On Fri, Nov 22, 2019 at 06:41:25PM +0100, Ard Biesheuvel wrote:
> Add support for SMMU drivers built as modules to the ACPI/IORT device
> probing path, by deferring the probe of the master if the SMMU driver is
> known to exist but has not been loaded yet. Given that the IORT code
> registers a platform device for each SMMU that it discovers, we can
> easily trigger the udev based autoloading of the SMMU drivers by making
> the platform device identifier part of the module alias.
> 
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> ---
>  drivers/acpi/arm64/iort.c   | 4 ++--
>  drivers/iommu/arm-smmu-v3.c | 1 +
>  drivers/iommu/arm-smmu.c    | 1 +
>  3 files changed, 4 insertions(+), 2 deletions(-)

I think it is best if Will picks this up and add it to the
series that modularize the SMMU drivers:

Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>

> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index 5a7551d060f2..a696457a9b11 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -850,9 +850,9 @@ static inline bool iort_iommu_driver_enabled(u8 type)
>  {
>  	switch (type) {
>  	case ACPI_IORT_NODE_SMMU_V3:
> -		return IS_BUILTIN(CONFIG_ARM_SMMU_V3);
> +		return IS_ENABLED(CONFIG_ARM_SMMU_V3);
>  	case ACPI_IORT_NODE_SMMU:
> -		return IS_BUILTIN(CONFIG_ARM_SMMU);
> +		return IS_ENABLED(CONFIG_ARM_SMMU);
>  	default:
>  		pr_warn("IORT node type %u does not describe an SMMU\n", type);
>  		return false;
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 7669beafc493..bf6a1e8eb9b0 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -3733,4 +3733,5 @@ module_platform_driver(arm_smmu_driver);
>  
>  MODULE_DESCRIPTION("IOMMU API for ARM architected SMMUv3 implementations");
>  MODULE_AUTHOR("Will Deacon <will@...nel.org>");
> +MODULE_ALIAS("platform:arm-smmu-v3");
>  MODULE_LICENSE("GPL v2");
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index d55acc48aee3..db5106b0955b 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -2292,4 +2292,5 @@ module_platform_driver(arm_smmu_driver);
>  
>  MODULE_DESCRIPTION("IOMMU API for ARM architected SMMU implementations");
>  MODULE_AUTHOR("Will Deacon <will@...nel.org>");
> +MODULE_ALIAS("platform:arm-smmu");
>  MODULE_LICENSE("GPL v2");
> -- 
> 2.20.1
>