[Skiboot] [PATCH 3/3] npu2/hw-procedures: Fix parallel zcal for opencapi

Stewart Smith stewart at linux.ibm.com
Wed Mar 20 17:31:24 AEDT 2019

Frederic Barrat <fbarrat at linux.ibm.com> writes:
> Le 18/03/2019 à 01:57, Andrew Donnellan a écrit :
>> On 16/3/19 3:44 am, Frederic Barrat wrote:
>>> For opencapi, we currently do impedance calibration when initializing
>>> the PHY for the device, which could run in parallel if we were rich
>>> and had multiple opencapi devices. But if 2 devices are on the same
>>> obus, the 2 calibration sequences could overlap, which likely yields
>>> bad results and is useless anyway since it only needs to be done once
>>> per obus.
>>> This patch splits the opencapi PHY reset in 2 parts:
>>> - a 'init' part called serially at boot. That's when zcal is done. If
>>>    we have 2 devices on the same socket, the zcal won't be redone,
>>>    since we're called serially and we'll see it has already be done for
>>>    the obus
>>> - a 'reset' part called during fundamental reset as a prereq for link
>>>    training. It does the PHY setup for a set of lanes and the dccal.
>>> The PHY team confirmed there's no dependency between zcal and the
>>> other reset steps and it can be moved earlier.
>>> Signed-off-by: Frederic Barrat <fbarrat at linux.ibm.com>
>> Does this need to go to stable?
> Yes, and I keep forgetting :-(
> This patch doesn't apply on v6.1. I'll backport it later this week.

We only really care about 6.0 and 6.2 at this point - and given about 2
weeks we won't care about 6.2 anymore.

Stewart Smith
OPAL Architect, IBM.

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