On Tue 07 Dec 08:56 PST 2021, Hans de Goede wrote: > Hi all, > > On 12/7/21 13:26, Heikki Krogerus wrote: > > +Hans and Imre > > > > On Mon, Dec 06, 2021 at 02:31:40PM -0800, Bjorn Andersson wrote: > >> On Thu 07 Oct 03:17 PDT 2021, Heikki Krogerus wrote: > >>> On Wed, Oct 06, 2021 at 01:26:35PM -0700, Prashant Malani wrote: > >>>> (CC+ Heikki) > >> [..] > >>>> On Wed, Oct 6, 2021 at 8:19 AM Doug Anderson <dianders@xxxxxxxxxxxx> wrote: > >> [..] > >>> void drm_connector_oob_hotplug_event(struct fwnode_handle *connector_fwnode); > >>> > >>> If your USB Type-C controller/port driver does not yet register the DP > >>> alt mode, the it's responsible of handling HPD separately by calling > >>> drm_connector_oob_hotplug_event() on its own. > >>> > >> > >> Finally found my way back to this topic and it doesn't look like I can > >> reuse the existing altmode code with the firmware interface provided by > >> Qualcomm, so I just hacked something up that invokes > >> drm_connector_oob_hotplug_event(). > >> > >> But I'm not able to make sense of what the expected usage is. Reading > >> altmode/displayport.c, it seems that I should only invoke > >> drm_connector_oob_hotplug_event() as HPD state toggles. > >> > >> I made a trial implementation of this, where my firmware interface > >> driver calls drm_connector_oob_hotplug_event() every time HPD state > >> changes and then in my oob_hotplug_event callback I flip the DP > >> controller between on and off. > >> > >> Unfortunately when I then connect my HDMI dongle, I get HPD state HIGH, > >> call the oob_hotplug_event, the DP driver powers up and concludes that > >> there's nothing connected to the dongle and goes to idle. I then connect > >> the HDMI cable to the dongle, the firmware sends me another message with > >> HPD irq and state HIGH, which I ignore because it's not a change in > >> state. > >> > >> In the end I hacked up drm_connector_oob_hotplug_event() to allow me to > >> pass the HPD state and this solves my problem. I can now distinguish > >> between connect, disconnect and attention. > >> > >> Can you please help shed some light on what I might be missing? > > The plan always was to pass some extra information, like the number > of available DP lanes (which can make training faster) along as > parameter to the drm_connector_oob_hotplug_event(). > > The merged version ended up not doing this because there were no > consumers, but passing additional info like HPD state definitely > is ok. > Thanks, that clarifies things. I think it makes sense to pass #lanes, as that would rule out the possibility of attempting to run 4 lanes per dpcd information over a 2-lane mux configuration as well. I will write up some patches. Regards, Bjorn
