On Wed, Dec 18, 2013 at 10:28:37AM -0600, Daniel Drake wrote:
On Wed, Dec 18, 2013 at 2:43 AM, Daniel Vetter daniel@ffwll.ch wrote:
I think we can do it simpler. When you get a hpd interrupt you eventually call drm_helper_hpd_irq_event which will update all the state and poke connectors. I'd just create a delay_work which you launch from hdmi_irq_thread with a 1 second delay which again calls drm_helper_hpd_irq_event. That way you won't miss the EDID (presuming the user isn't _really_ careful with pluggin in the cable slowly).
OK, I like this more simplistic option.
However, one more pesky detail, if I am understanding your suggestion correctly. You are hoping for:
- I connect the display, causing HPD interrupt
- hpd irq handler calls drm_helper_hpd_irq_event() directly. Fails to
read EDID, no big deal. 3. hpd irq handles schedules a work item to call drm_helper_hpd_irq_event() a second time, 1 second later. Reads EDID sucessfully, image gets output to display.
That doesn't quite work. drm_helper_hpd_irq_event() in step 2 notices and records the state change (disconnected --> connected). And after drm_helper_probe_single_connector_modes() fails to read the EDID, it starts outputting an image at 1024x768. When we come to step 3, we call drm_helper_hpd_irq_event again, but that just returns without doing anything as it does not detect any new state change.
If we skip step 2, i.e. always delay the call to drm_helper_hpd_irq_event by 1 second, the problem is solved. As a user, the 1 second delay is not noticable. What do you think about just doing this?
Oh right, if you use the hpd pin for detection then this will happen. So I guess always delaying is the right option. Or you could make the connector state only conditional on an edid being present for HDMI, which would also work. -Daniel