[RFC PATCH v2 0/8] ACPI/IORT: Support for IORT RMR node

[Steven Price]

On 19/11/2020 12:11, Shameer Kolothum wrote:
> RFC v1 --> v2:
>   - Added a generic interface for IOMMU drivers to retrieve all the
>     RMR info associated with a given IOMMU.
>   - SMMUv3 driver gets the RMR list during probe() and installs
>     bypass STEs for all the SIDs in the RMR list. This is to keep
>     the ongoing traffic alive(if any) during SMMUv3 reset. This is
>     based on the suggestions received for v1 to take care of the
>     EFI framebuffer use case. Only sanity tested for now.

Hi Shameer,

Sorry for not looking at this before.

Do you have any plans to implement support in the SMMUv2 driver? The 
platform I've been testing the EFI framebuffer support on has the 
display controller behind SMMUv2, so as it stands this series doesn't 
work. I did hack something up for SMMUv2 so I was able to test the first 
4 patches.

>   - During the probe/attach device, SMMUv3 driver reserves any
>     RMR region associated with the device such that there is a unity
>     mapping for them in SMMU.

For the EFI framebuffer use case there is no device to attach so I 
believe we are left with just the stream ID in bypass mode - which is 
definitely an improvement (the display works!) but not actually a unity 
mapping of the RMR range. I'm not sure whether it's worth fixing this or 
not, but I just wanted to point out there's still a need for a driver 
for the device before the bypass mode is replaced with the unity mapping.

Thanks,

Steve