[Skiboot] [PATCH skiboot] npu2: Clear fence on all bricks

[Reza Arbab]

On Fri, Nov 22, 2019 at 11:04:22AM +1100, Alexey Kardashevskiy wrote:
>Reza/Ryan, could you please add more details about what exactly causes
>these UR HMIs? Thanks!

Hopefully I've pieced together the bug history correctly. As I 
understand it...

Each GPU has a 640kb protected region which will result in a 
"unsupported request" (UR) response. The root bug is that the driver 
maps and accidentally accesses that area.

This firmware patch helps for recovery. From our perspective it may seem 
redundant to clear the fence on all bricks instead of just the one we're 
resettting, but at a hardware level the above UR sends a fence signal to 
all the hardware units so they all need to be cleared.

Acked-by: Reza Arbab <arbab at linux.ibm.com>

-- 
Reza Arbab