On Wed, 12 Sep 2018, Alexandre Belloni wrote:

On 12/09/2018 12:43:52+0100, Lee Jones wrote:

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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.

I care for the kernel in general, not just the areas I'm responsible
for.  I guess I'm just that kinda guy! ;)

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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.

Oh I see.  My question was relating to whether the H/W is physically
capable of changing modes on-the-fly, rather than how Linux would
handle that.  If this is something we'd wish to support, then it would
have to be a single driver, which is why I was asking.  By separating
the drivers this way, we are blocking that as a possibility.  Although
I guess the OP has already thought about that and made the decision
not to support it.

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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.

Other drivers already do this.

-- 
Lee Jones [???]
Linaro Services Technical Lead
Linaro.org ? Open source software for ARM SoCs
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