[Bug 109112] "*ERROR* Failed to probe lspcon" when HDMI isn't plugged before boot

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109112

--- Comment #35 from Kai-Heng Feng <kai.heng.feng at canonical.com> ---
(In reply to shashank.sharma at intel.com from comment #34)
> In the motherboard down mode, LSPCON is supposed to be powered on with the
> power supply from the board, and hence, it was supposed to be powered-on
> during the driver probe time. So if it's not getting powered on during
> probe, this seems like a board design error, and not a SW issue. (This is
> probably expecting LSPCON to work in dongle mode, which we do not support in
> driver). That also explains why we are not able to reproduce this issue with
> other parade based devices.

Ok we'll let vendor know about this.

> 
> In order to work around this issue, we can add LSPCON probing in the
> hot-plug sequence, but that might come up with its own hotplug stability
> issues, like if the I2C over Aux bus is not stable yet, that might delay the
> hotplug handling path by adding some retries.

We can use a DMI based quirk so other platforms won't be penalized.

> 
> Also, this is only possible when the display master IRQ is getting the HPD
> interrupt, but it's getting missed due to unavailability on the connector on
> port. But as the IRQ signal is also coming via LSPCON, which is not
> powered-on until hotplug, there is also a possibility of missing the hotplug
> all-together, in which case, moving the probe is not going to help at all.

This doesn't explain why Windows doesn't have this issue, it can reliably
detect hot plugging event everytime.

>  
> - Shashank

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