[Skiboot] [PATCH] npu2/hw-procedures: Fence bricks via NTL instead of MISC

[Stewart Smith]

Reza Arbab <arbab at linux.ibm.com> writes:
> There are a couple of places we can set/unset fence for a brick:
>
> 1. MISC register: NPU2_MISC_FENCE_STATE
> 2. NTL register for the brick: NPU2_NTL_MISC_CFG1(ndev)
>
> Recent testing of ATS in combination with GPU reset has exposed a side
> effect of using (1); if fence is set for all six bricks, it triggers a
> sticky nmmu latch which prevents the NPU from getting ATR responses.
> This manifests as a hang in the tests.
>
> We have npu2_dev_fence_brick() which uses (1), and only two calls to it.
> Replace the call which sets fence with a write to (2). Remove the
> corresponding unset call entirely. It's unneeded because the procedures
> already do a progression from full fence to half to idle using (2).
>
> Signed-off-by: Reza Arbab <arbab at linux.ibm.com>
> ---
>  hw/npu2-hw-procedures.c | 31 +++++++------------------------
>  1 file changed, 7 insertions(+), 24 deletions(-)

Thanks, seeing as we want this for stable as well, merged to:
master as of 5ff8763c9b0421d8de0f4346ca211c853d2406d4
6.0.x as of 966a2839484f164979c5118e52928f8509b4982b

-- 
Stewart Smith
OPAL Architect, IBM.