Re: [PATCH v2 3/7] iommu/arm-smmu: Add dependency on io-pgtable format modules

From: Robin Murphy <robin.murphy@arm.com>
To: isaacm@codeaurora.org
Cc: kernel-team@android.com, will@kernel.org, pdaly@codeaurora.org,
	linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org,
	iommu@lists.linux-foundation.org,
	freedreno@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org, pratikp@codeaurora.org
Subject: Re: [PATCH v2 3/7] iommu/arm-smmu: Add dependency on io-pgtable format modules
Date: Wed, 23 Dec 2020 13:05:25 +0000	[thread overview]
Message-ID: <b86f5972-2e9c-20bd-eee3-ee3ea53d5fe6@arm.com> (raw)
In-Reply-To: <e47f14b81d90772346ef28c9a7fd3365@codeaurora.org>

On 2020-12-22 19:49, isaacm@codeaurora.org wrote:
> On 2020-12-22 11:27, Robin Murphy wrote:
>> On 2020-12-22 00:44, Isaac J. Manjarres wrote:
>>> The SMMU driver depends on the availability of the ARM LPAE and
>>> ARM V7S io-pgtable format code to work properly. In preparation
>>
>> Nit: we don't really depend on v7s - we *can* use it if it's
>> available, address constraints are suitable, and the SMMU
>> implementation actually supports it (many don't), but we can still
>> quite happily not use it even so. LPAE is mandatory in the
>> architecture so that's our only hard requirement, embodied in the
>> kconfig select.
>>
>> This does mean there may technically still be a corner case involving
>> ARM_SMMU=y and IO_PGTABLE_ARM_V7S=m, but at worst it's now a runtime
>> failure rather than a build error, so unless and until anyone
>> demonstrates that it actually matters I don't feel particularly
>> inclined to give it much thought.
>>
>> Robin.
>>
> Okay, I'll fix up the commit message, as well as the code, so that it
> only depends on io-pgtable-arm.

Well, IIUC it would make sense to keep the softdep for when the v7s 
module *is* present; I just wanted to clarify that it's more of a 
nice-to-have rather than a necessity.

Robin.

> Thanks,
> Isaac
>>> for having the io-pgtable formats as modules, add a "pre"
>>> dependency with MODULE_SOFTDEP() to ensure that the io-pgtable
>>> format modules are loaded before loading the ARM SMMU driver module.
>>>
>>> Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
>>> ---
>>>   drivers/iommu/arm/arm-smmu/arm-smmu.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c 
>>> b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>>> index d8c6bfd..a72649f 100644
>>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
>>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>>> @@ -2351,3 +2351,4 @@ MODULE_DESCRIPTION("IOMMU API for ARM 
>>> architected SMMU implementations");
>>>   MODULE_AUTHOR("Will Deacon <will@kernel.org>");
>>>   MODULE_ALIAS("platform:arm-smmu");
>>>   MODULE_LICENSE("GPL v2");
>>> +MODULE_SOFTDEP("pre: io-pgtable-arm io-pgtable-arm-v7s");
>>>
>>
>> _______________________________________________
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>> linux-arm-kernel@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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