Re: [PATCH] soc: qcom: pmic_glink_altmode: fix spurious DP hotplug events

[Clayton Craft]

On 3/26/25 07:43, Johan Hovold wrote:
> On Tue, Mar 25, 2025 at 09:32:10AM +0100, Johan Hovold wrote:
> > On Mon, Mar 24, 2025 at 10:05:44AM -0700, Clayton Craft wrote:
> > > On 3/24/25 06:24, Johan Hovold wrote:
> > > > The PMIC GLINK driver is currently generating DisplayPort hotplug
> > > > notifications whenever something is connected to (or disconnected from)
> > > > a port regardless of the type of notification sent by the firmware.
> > > >
> > > > These notifications are forwarded to user space by the DRM subsystem as
> > > > connector "change" uevents:
> >
> > > > ---
> > > >
> > > > Clayton reported seeing display flickering with recent RC kernels, which
> > > > may possibly be related to these spurious events being generated with
> > > > even greater frequency.
> > > >
> > > > That still remains to be fully understood, but the spurious events, that
> > > > on the X13s are generated every 90 seconds, should be fixed either way.
> > >
> > > When a display/dock (which has ethernet) is connected, I see this
> > > hotplug change event 2 times (every 30 seconds) which I think you said
> > > this is expected now?
> >
> > I didn't realise you were also using a display/dock. Bjorn mentioned
> > that he has noticed issues with one of his monitors (e.g. built-in hub
> > reenumerating repeatedly iirc) which may be related.

Sorry for the confusion, let me clarify:

The original issue I reported to you on IRC was *without* a 
dock/external display attached, only a PD adapter was attached. With 
your patch, I no longer see these drm hotplug events in this scenario.

After confirming that your patch resolved the spurious hotplug events 
when using a PD charger, I connected a dock+external display to see if 
the patch caused any regressions there for me. It was here that I 
noticed a periodic hotplug event firing 2 times every 30 seconds was 
still showing up. I don't know if this is expected or not, I've never 
noticed it before because I wasn't monitoring udev events.

> > Just so I understand you correctly here, you're no longer seeing the
> > repeated uevents with this patch? Both when using a dock and when using
> > a charger directly?

With PD charger only: no more spurious hotplug events firing

With dock+external displauy: 2x hotplug events every 30s.

> > Did it help with the display flickering too? Was that only on the
> > external display?

The flickering was only on the internal display, and your patch here 
seems to have resolved that.

-Clayton