iommu/arm-smmu: Correctly calculate and use the TTBR1 pagetable

Due to an egregious misunderstanding of the specification it
was thought that to do the TTBR1 matching correctly the sign
extension bit needed to match the input address space. This
is incorrect - the TTBR1 range is determined by the size of
the TTBR1 space (in our case, the same as the input address
space). For example if the input address size is 36, the
effective range of the pagetables are:

TTBR0: 0x00000000_00000000 - 0x0000000f_ffffffff
TTBR1: 0xfffffff0_00000000 - 0xffffffff_ffffffff

For its part the sign extension bit needs should be set based on
the upstream bus size. If the device has a UBS of 49 then the
sign extension bit is assumed by design to be 48 otherwise
the driver needs to pick the highest available bit and reduce
the input address space by 1.

Because the client driver shouldn't need to know the upstream
bus size, convention is to use a fully sign extended unsigned
long address for TTBR1 mappings. If the sign extension bit is set
lower than the upstream bus size some implementations assume that
bits above the sign extension bit need to be zero and breaks the
convention. Setting the sign extension bit correctly for the
upstream bus size ensures that sign extension always works.

The hardware will match an address to the TTBR1 if all the bits
between the sign extension bit and the input address size are set
to 1. We emulate this behavior in software when looking up a pagetable
for a software operation.

Change-Id: Ic0dedbad80c72f11bc8a7e6792f0e3c2f58bc674
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>

0 files changed, 0 insertions, 0 deletions