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

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Date:   Mon, 25 Nov 2019 12:16:54 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Ard Biesheuvel <ardb@...nel.org>, will@...nel.org
Cc:     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, lorenzo.pieralisi@....com,
        saravanak@...gle.com
Subject: Re: [PATCH] iommu/arm-smmu: support SMMU module probing from the IORT

On 22/11/2019 5:41 pm, 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.

Thanks Ard, I was just gearing up to check the ACPI fallout myself :)

AFAICS this looks sufficient to avoid any unexpected behaviour if users 
start playing with the rest of the series on ACPI systems, so we can 
investigate 'proper' device links for IORT at some point in future.

Reviewed-by: Robin Murphy <robin.murphy@....com>

> 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(-)
> 
> 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");
>