[PATCH next] cxl: Allow PSL timebase to not sync

Vaibhav Jain vaibhav at linux.vnet.ibm.com
Tue Mar 15 15:09:29 AEDT 2016

Hi Mikey,

Michael Neuling <mikey at neuling.org> writes:

> I'm not happy with doing this unless we add something which advertises
> that it's synced or not to userspace.
> If we do that, I'm happy to just fail without the need of the parameter
> but advertise it to userspace.
> The parameter is a bit of a PITA too, as it's a driver level config not
> card level.  You really want to turn it on/off based on the card, not
> the whole system.

Would a bool attribute in sysfs for the card (e.g timebase_sync) make
sense? We can by default ignore (and log) timebase sync errors during card
initialization and provide a simple wrapper in libcxl to query and set
this attribute afterwards.

Also it might be better if the AFU advertises the need for timebase
synchronization via a configuration record so that we enable it for the
psl iif one of the slices asks for it. I am not sure if this possible at
the moment but I believe it something we can put forth the psl/hdk team
before timebase usage becomes more widespread.

~ Vaibhav

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