Re: [RFC 1/3 v3] mm: iommu: An API to unify IOMMU, CPU and devicememory management

[Russell King - ARM Linux]

On Thu, Jul 15, 2010 at 08:48:36PM -0400, Tim HRM wrote:
> Interesting, since I seem to remember the MSM devices mostly conduct
> IO through regions of normal RAM, largely accomplished through
> ioremap() calls.
> 
> Without more public domain documentation of the MSM chips and AMSS
> interfaces I wouldn't know how to avoid this, but I can imagine it
> creates a bit of urgency for Qualcomm developers as they attempt to
> upstream support for this most interesting SoC.

As the patch has been out for RFC since early April on the linux-arm-kernel
mailing list (Subject: [RFC] Prohibit ioremap() on kernel managed RAM),
and no comments have come back from Qualcomm folk.

The restriction on creation of multiple V:P mappings with differing
attributes is also fairly hard to miss in the ARM architecture
specification when reading the sections about caches.
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