Re: [PATCH v12 0/6] Driver for at91 usart in spi mode

Alexandre Belloni
2018-09-12T12:14:34Z

On 12/09/2018 12:43:52+0100, Lee Jones wrote:
> > > But ... we can't have it both ways. *Either* it's a true MFD, in
> > > which case it can/should have 2 separate compatible strings which can
> > > be specified directly from the DT. *Or* it's not an MFD. In the
> > > latter case, which I think we're all agreeing on (else we'd have 2
> > > compatible strings), MFD is not the place to handle this (my original
> > > point).
> > >
> >
> > If that is what bothers you, then let's move it out of mfd.
>
> As I've already mentioned. I don't just want it moved out of MFD and
> shoved somewhere else. My aim is to fix this properly.
>

If it is out of MFD, then I'm not sure why you would care too much about
it as you won't be maintaining that code. And I still this what was done
was correct but I'm open to test what you suggest.

> > > So ... this is a USART device which can do SPI, right?
> > >
> > > My current thinking is that; as this is a USART device first &
> > > foremost, the USART should be probed in the first instance regardless,
> > > then if SPI mode is specified it (the USART driver) registers the SPI
> > > platform driver (as MFD does currently) and exits gracefully, allowing
> > > the SPI driver to take over.
> > >
> > > Spanner in the works: is it physically possible to change the mode at
> > > run-time? :s
> >
> > Yes it is possible but on Linux that will not happen without probing
> > the drivers again.
>
> Not sure I understand what you mean.
>

I was just commenting on changing the mode at runtime.

> I'm suggesting that you use the same platform_* interfaces MFD uses to
> register the SPI driver if SPI mode has been selected. Only do so
> from the appropriate driver i.e. USART.
>

Yeah, I understood that but I didn't comment because I'm not sure this
will work yet.

--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering