Re: [PATCH v8] PCI: hotplug: Add a generic RAS tracepoint for hotplug event

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Tue, 20 May 2025, Lukas Wunner wrote:

> On Tue, May 20, 2025 at 12:44:38PM +0200, Lukas Wunner wrote:
> > Link speed changes and device plug/unplug events are orthogonal,
> > I don't think they should be mixed together in the same event.
> > 
> > A link speed event can be signaled simultaneously to a plug event
> > and then user space can decide in which type of event it's
> > interested in.
> > 
> > That also avoids the awkwardness of having N/A values for the
> > link speed on unplug.
> 
> After thinking about this some more:
> 
> A link speed event could contain a "reason" field
> which indicates why the link speed changed,
> e.g. "hotplug", "autonomous", "thermal", "retrain", etc.
> 
> In other words, instead of mixing the infomation for hotplug
> and link speed events together in one event, a separate link
> speed event could point to hotplug as one possible reason for
> the new speed.

It will be somewhat challenging to link LBMS into what caused it, 
especially in cases where there is more than one LBMS following a single 
Link Retraining.

Do you have opinion on should the event be only recorded from LBMS/LABS 
if the speed changed from the previous value? The speed should probably 
also be reported also for the first time (initial enumeration, hotplugging 
a new board).

-- 
 i.