Re: [PATCH 1/2] drm/msm/dp: postpone irq_hpd event during connection pending state
From: khsieh
Date: Thu Jan 14 2021 - 12:15:26 EST
On 2021-01-13 16:00, Stephen Boyd wrote:
Quoting khsieh@xxxxxxxxxxxxxx (2021-01-13 15:44:32)
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).
Ok. So nobody understands why the hardware is acting this way and we're
papering over the problem by forcing the HPD state to be what we think
it should be? That's not great.
irq_hpd is issued from dongle.
it then go through EC ps8805 driver and reach DP driver finally.
Again, to duplicate problem #1 this at my set up, i have to
intentionally wiggling type-c connector of dongle.
But I can not duplicate problem #2 and only saw it one time from Quantan
provide logs.