Re: [PATCH 1/2] drm/msm/dp: postpone irq_hpd event during connection pending state

[khsieh]

On 2021-01-13 12:22, Stephen Boyd wrote:
> Quoting khsieh@xxxxxxxxxxxxxx (2021-01-13 09:44:24)
> > On 2021-01-11 11:55, Stephen Boyd wrote:
> > > Quoting Kuogee Hsieh (2021-01-07 12:30:24)
> > >> irq_hpd event can only be executed at connected state. Therefore
> > >> irq_hpd event should be postponed if it happened at connection
> > >> pending state. This patch also make sure both link rate and lane
> > >
> > > Why does it happen at connection pending state?
> > plug in need two state to complete it.
> > advance to connection pending state once link training completed and
> > sent uevent notification to frame work.
> > transition to connected state after frame work provided resolution
> > timing and start transmit video panel.
> > Therefore irq_hpd should not be handled if it occurred before 
> > connected
> > state.
>
> Sure that's what's going on in the patch but you didn't answer my
> question. Why does irq_hpd happen before connected state?

I have no idea why it happen this way.
during debug 
https://partnerissuetracker.corp.google.com/issues/170598152
I saw two different scenario
1) irq_hpd followed by unplug with less than 20 ms in between. this one 
fixed by this patch set.
2) plug followed by irq_hpd around 300ms in between. it does not cause 
problem. but it should be handled in order (after connected state).