On Mon, Apr 08, 2024 at 12:43:34PM -0700, Abhinav Kumar wrote:
>
>
> On 4/7/2024 11:48 AM, Bjorn Andersson wrote:
> > On Fri, Apr 05, 2024 at 08:15:47PM -0700, Abhinav Kumar wrote:
> > > From: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> > [..]
> > > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> > > index d80f89581760..bfb6dfff27e8 100644
> > > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > > @@ -1665,7 +1665,7 @@ void dp_bridge_hpd_notify(struct drm_bridge *bridge,
> > > return;
> > > if (!dp_display->link_ready && status == connector_status_connected)
> > > - dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
> > > + dp_hpd_plug_handle(dp, 0);
> >
> > If I read the code correctly, and we get an external connect event
> > inbetween a previous disconnect and the related disable call, this
> > should result in a PLUG_INT being injected into the queue still.
> >
> > Will that not cause the same problem?
> >
> > Regards,
> > Bjorn
> >
>
> Yes, your observation is correct and I had asked the same question to kuogee
> before taking over this change and posting.
>
> We will have to handle that case separately. I don't have a good solution
> yet for it without requiring further rework or we drop the below snippet.
>
> if (state == ST_DISCONNECT_PENDING) {
> /* wait until ST_DISCONNECTED */
> dp_add_event(dp, EV_HPD_PLUG_INT, 0, 1); /* delay = 1 */
> mutex_unlock(&dp->event_mutex);
> return 0;
> }
>
> I will need sometime to address that use-case as I need to see if we can
> handle that better and then drop the the DISCONNECT_PENDING state to address
> this fully. But it needs more testing.
>
> But, we will need this patch anyway because without this we will not be able
> to fix even the most regular and commonly seen case of basic
> connect/disconnect receiving complementary events.
>
I did some more testing on this patch. Connecting and disconnecting the
cable while in fbcon works reliably, except for:
- edid/modes are not read before we bring up the link so I always end up
with 640x480
- if I run modetest -s <id>:<mode> the link is brought up with the new
resolution and I get my test image on the screen.
But as we're shutting down the link for the resolution chance I end up
in dp_bridge_hpd_notify() with link_ready && state = disconnected.
This triggers an unplug which hangs on the event_mutex, such that as
soon as I get the test image, the state machine enters
DISCONNECT_PENDING. This is immediately followed by another
!link_ready && status = connected, which attempts to perform the plug
operation, but as we're in DISCONNECT_PENDING this is posted on the
event queue. From there I get a log entry from my PLUG_INT, every
100ms stating that we're still in DISCONNECT_PENDING. If I exit
modetest the screen goes black, and no new mode can be selected,
because we're in DISCONNECT_PENDING. The only way out is to disconnect
the cable to complete the DISCONNECT_PENDING.
Regards,
Bjorn
>
> > > else if (dp_display->link_ready && status == connector_status_disconnected)
> > > - dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
> > > + dp_hpd_unplug_handle(dp, 0);
> > > }
> > > --
> > > 2.43.2
> > >
