[PATCH] drivers/tty/serial/8250: Make Aspeed VUART SIRQ polarity configurable

Jeremy Kerr jk at ozlabs.org
Mon Jul 29 12:02:56 AEST 2019

Hi Oskar,

> In my understanding the SIRQ polarity should be the same for all UARTs
> on the particular bus, i.e. both UARTs controlled by the SuperI/O and
> the VUART or PUART (pass-through). However, the host controls the
> UARTs on the SuperI/O itself.

Somewhat offtopic, but are you sure you want to enable the SuperIO

>  The VUART is covered by this code and we don't have a PUART driver
> yet.
> It might make sense to have this as a global setting which each driver
> could read. But wouldn't this be an exercise for the future where we
> actually have a second device? I don't think the Aspeed currently has
> any other devices that could generate a SIRQ (except for the PUART for
> which there's no driver).

We have a bunch of SIRQ sources that we use (on OpenPOWER platforms) -
the BT interface, the KCS interface, the UARTs, and the mbox hardware.
It's not just the VUART/PUART :)

> Having said that, ideally I'd like the SIRQ polarity to be auto-
> configured from the LPC/eSPI HW pin strap anyway. I have the code for
> that almost done. Maybe we shouldn't even have the sysfs interface for
> it and I should strip that out?

Yeah, I think I agree with that. The only downside is that the 
individual drivers will now need to poke at the SCU to query the
LPC/eSPI configuration. If you can find a nice way to do that, then that
sounds like the best approach. Can you query it through the parent bus



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