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@chromium.org 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?
Thanks, Bjorn