On Wed, Jul 19, 2017 at 4:27 PM, Robin Murphy [off-list ref] wrote:

On 19/07/17 10:33, Anup Patel wrote:

quoted

This patchset primarily adds Broadcom FlexRM reset module for
VFIO platform driver. We also have minor improvments in IOMMU
and VFIO driver to allow VFIO no-IOMMU mode access to FlexRM.

I'm struggling to understand the IOMMU changes here - what's the
FlexRM's hardware relationship with the IOMMU, and how is it different
from any other device? Furthermore, if there *is* a relevant IOMMU
present, why would no-IOMMU mode need to be involved at all?

We want to have FlexRM device accessible from user-space
using VFIO platform with and without IOMMU.

Currently, if IOMMU ops are available for platform bus then
I cannot access FlexRM device using VFIO no-IOMMU mode.

Since, SMMU can bypass transactions which do not match
any SMRs, we should allow no-IOMMU mode for devices
when IOMMU group is not available.

Regards,
Anup