+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? Originally I wanted an API that we could use to pass all the details that we have in the USB Type-C drivers (that would be the configuration and status) to the GPU drivers, but Hans was against that because, if I remember correctly, the OOB hotplug event may need to be delivered to the GPU drivers in some cases even when the connector is not USB Type-C connector, and he wanted a common API. Hans, please correct me if I got it wrong. I think that the GPU drivers need to handle USB Type-C connectors separately one way or the other, but maybe the notification from the connector can continue to be generic - not USB Type-C specific. Imre proposed that the GPU drivers should be able to query the DisplayPort configuration and status from the USB Type-C drivers instead of the USB Type-C drivers just dumping the information together with the notification about some event (so connection, disconnection or attention) like I originally proposed. Imre, please correct me if I misunderstood you :-). I'm fine with anything, but we do need improvement here as you guys can see. thanks, -- heikki
