[Skiboot] [PATCH v3] phb4: Check for RX errors after link training

Stewart Smith stewart at linux.vnet.ibm.com
Fri Nov 2 18:59:10 AEDT 2018

Michael Neuling <mikey at neuling.org> writes:
> From: Oliver O'Halloran <oohall at gmail.com>
> Some PHB4 PHYs can get stuck in a bad state where they are constantly
> retraining the link. This happens transparently to skiboot and Linux
> but will causes PCIe to be slow. Resetting the PHB4 clears the
> problem.
> We can detect this case by looking at the RX errors count where we
> check for link stability. This patch does this by modifying the link
> optimal code to check for RX errors. If errors are occurring we
> retrain the link irrespective of the chip rev or card.
> Normally when this problem occurs, the RX error count is maxed out at
> 255. When there is no problem, the count is 0. We chose 8 as the max
> rx errors value to give us some margin for a few errors. There is also
> a knob that can be used to set the error threshold for when we should
> retrain the link. ie
>   nvram -p ibm,skiboot --update-config phb-rx-err-max=8
> Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
> Signed-off-by: Michael Neuling <mikey at neuling.org>


Figured this should also go to stable as everybody's been asking me,
so merged to master as of 9597a12ef4b3644e4b8644f659bec04ca139b7f9
and to 6.0.x as of 125cecaa0f236cc01cf527b432f74e4de69f3d12,  which made
it into 6.0.11

Stewart Smith
OPAL Architect, IBM.

More information about the Skiboot mailing list