On Wed, Jan 31, 2018 at 12:10:47PM +0000, Shameerali Kolothum Thodi wrote:

[...]

quoted

I went back and re-read the patches, I think the point here is that the
perf driver (ie PATCH 2 that, by the way, is not maiinline) uses
devm_ioremap_resource() to map the counters and that's what is causing
failures when PMCG is part of SMMUv3 registers.

Thanks for going through this.  No, this is not where we are seeing the failure.
May be I was not clear in my earlier mail. The failure happens in SMMUv3
driver probe function when it calls devm_ioremap_resource().

Understood - because the PMU PMCG driver calls it first, that's what
I was referring to.

My point is that:

- the PMCG platform device resources should be built with the correct
  resource hierarchy
- and even then, I do not think that using devm_ioremap_resource() in
  the PMCG PMU driver is the correct way of handling its resource
  reservation (ie the kernel must be able to detect that a resource is
  contained in a parent one but I am not sure devm_ioremap_resource()
  is the way to handle this correctly)

quoted

It is the resources hierarchy that is wrong and in turn, I do not think
devm_request_mem_region() is the right way of requesting it for the
PMCG driver.

I need to look into this but I suspect that's something that should
be handled in the PMCG driver, that has to request the memory region
_differently_ (ie ioremap copes with this overlap - it is the
devm_request_mem_region() in devm_ioremap_resource() that fails, correct
?).

It looks like, in IORT code,

iort_add_platform_device()--> platform_device_add()-->insert_resource(), inserts
both SMMUv3 and PMCG resources into the resource tree and then when the probe
of SMMUv3 is called, it detects the conflict.

[   85.548749] arm-smmu-v3 arm-smmu-v3.0.auto: can't request region for resource [mem 0x148000000-0x14801ffff]                      

Of course, changing devm_ioremap_resource() to devm_ioremap() in SMMv3
driver probe solves the issue for us, but not sure that's the right approach or not.

See above.

Lorenzo