[PATCH v3 0/3] perf/smmuv3: Don't reserve the PMCG register spaces

[Leizhen (ThunderTown)]

On 2021/1/29 4:31, Will Deacon wrote:
> On Wed, Jan 27, 2021 at 07:32:55PM +0800, Zhen Lei wrote:
>> v2 --> v3:
>> Patch 3 is updated because https://lkml.org/lkml/2021/1/22/532 has been queued in advance.
>>
>> v1 --> v2:
>> According to Robin Murphy's suggestion: https://lkml.org/lkml/2021/1/20/470
>> Don't reserve the PMCG register spaces, and reserve the entire SMMU register space.
>>
>> v1:
>> Since the PMCG may implement its resigters space(4KB Page0 and 4KB Page1)
>> within the SMMUv3 64KB Page0. In this case, when the SMMUv3 driver reserves the
>> 64KB Page0 resource in advance, the PMCG driver try to reserve its Page0 and
>> Page1 resources, a resource conflict occurs.
>>
>> commit 52f3fab0067d6fa ("iommu/arm-smmu-v3: Don't reserve implementation
>> defined register space") reduce the resource reservation range of the SMMUv3
>> driver, it only reserves the first 0xe00 bytes in the 64KB Page0, to avoid
>> the above-mentioned resource conflicts.
>>
>> But the SMMUv3.3 add support for ECMDQ, its registers space is also implemented
>> in the SMMUv3 64KB Page0. This means we need to build two separate mappings.
>> New features may be added in the future, and more independent mappings may be
>> required. The simple problem is complicated because the user expects to map the
>> entire SMMUv3 64KB Page0.
>>
>> Therefore, the proper solution is: If the PMCG register resources are located in
>> the 64KB Page0 of the SMMU, the PMCG driver does not reserve the conflict resources
>> when the SMMUv3 driver has reserved the conflict resources before. Instead, the PMCG
>> driver only performs devm_ioremap() to ensure that it can work properly.
>>
>> Zhen Lei (3):
>>   perf/smmuv3: Don't reserve the PMCG register spaces
>>   perf/smmuv3: Add a MODULE_SOFTDEP() to indicate dependency on SMMU
>>   iommu/arm-smmu-v3: Reserving the entire SMMU register space
> 
> I'll need Robin's ack on these.

Hi, Robin:
  What's your opinion?
  In fact, I have written the patches that SMMU and PMCG whoever come first
will reserve the resources, and whoever comes next does not reserve. However,
the processing logic is relatively complex.

> 
> Will
> 
> .
>