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

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.