On Tue, 9 Apr 2024 at 00:23, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
>
>
>
> On 4/8/2024 2:12 PM, Dmitry Baryshkov wrote:
> > On Mon, 8 Apr 2024 at 22:43, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> 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.
> >
> > Should it then have the Co-developed-by trailers?
> >
>
> hmmm, perhaps but that didnt result in any code change between v2 and
> v3, so I didnt add it.
So who authored v0 of it? From your text I had an impression that it
was Kuogee. Please excuse me if I was wrong.
>
> >> 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.
> >
> > Hmm, no. We need to drop the HPD state machine, not to patch it. Once
> > the driver has proper detect() callback, there will be no
> > complementary events. That is a proper way to fix the code, not these
> > kinds of band-aids patches.
> >
>
> I had discussed this part too :)
>
> I totally agree we should fix .detect()'s behavior to just match cable
> connect/disconnect and not link_ready status.
>
> But that alone would not have fixed this issue. If HPD thread does not
> get scheduled and plug_handle() was not executed, .detect() would have
> still returned old status as we will update the cable status only in
> plug_handle() / unplug_handle() to have a common API between internal
> and external hpd execution.
I think there should be just hpd_notify, which if the HPD is up,
attempts to read the DPCD. No need for separate plug/unplug_handle.
The detect() can be as simple as !drm_dp_is_branch() || sink_count != 0.
>
> So we need to do both, make .detect() return correct status AND drop hpd
> event thread processing.
>
> But, dropping the hpd event thread processing alone was fixing the
> complimentary events issue. So kuogee had only this part in this patch.
I'd prefer to wait for the final patchset then. Which has the HPD
thread completely removed.
>
>
> >>>> 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
> >>>>
> >
> >
> >
--
With best wishes
Dmitry
