Re: [PATCH v6 0/8] mfd: introduce a driver for LPSS devices on SPT

[Lee Jones]

On Tue, 28 Jul 2015, Rafael J. Wysocki wrote:

> On Monday, July 27, 2015 10:29:34 PM Lee Jones wrote:
> > On Mon, 27 Jul 2015, Lee Jones wrote:
> > 
> > > On Mon, 27 Jul 2015, Rafael J. Wysocki wrote:
> > > 
> > > > On Monday, July 27, 2015 05:24:13 PM Lee Jones wrote:
> > > > > On Mon, 27 Jul 2015, Mika Westerberg wrote:
> > > > > 
> > > > > > On Mon, Jul 27, 2015 at 04:27:33PM +0100, Lee Jones wrote:
> > > > > > > FAO Stephen Boyd,
> > > > > > > 
> > > > > > > > Stephen, can you, please, have a look into patch 8 regarding to clock name
> > > > > > > > matching and other stuff Lee asked?
> > > > > > > 
> > > > > > > Patch 8:
> > > > > > > 
> > > > > > >       "Can you review the clock implementation please?  It looks
> > > > > > >       fragile to me as it relies heavily on device names constructed
> > > > > > >       of MFD cell names and IDA numbers cat'ed together!"
> > > > > > 
> > > > > > Lee, can you suggest an alternative then?
> > > > > > 
> > > > > > Why we are doing it like this is that number of different LPSS devices
> > > > > > changes from SoC to SoC. In addition to that the device (called "slice")
> > > > > > might have iDMA block or not.
> > > > > > 
> > > > > > Since the drivers in question (pxa2xx-spi, i2c-designware and 8250_dw)
> > > > > > use standard clk framework to request their clocks the Linux device must
> > > > > > have clock registered which matches the device in advance.
> > > > > > 
> > > > > > Because we add the host controller device dynamically (from the MFD
> > > > > > driver) based on how many devices are actually present, we need somehow
> > > > > > predict what would be the correct name and instance number for that
> > > > > > device to get the clock for it. That's the reason we use IDA here along
> > > > > > with the cell name (or driver name).
> > > > > 
> > > > > I'm sure there are perfectly viable reasons for you doing this.  And I
> > > > > don't know the CCF well enough to know whether it's the best idea or
> > > > > not, or else I would have made a suggestion rather than waiting all
> > > > > this time.
> > > > > 
> > > > > It's for this reason that I needed Mike (now Stephen) to take a look
> > > > > and give me either an Ack, to say it's the best solution, or to
> > > > > provide a better alternative.
> > > > > 
> > > > > Until that happens, I'm stuck!
> > > > 
> > > > Well, what if we had no one at hand to review that code?  Would that mean it
> > > > would not be applicable forever?
> > > 
> > > No, but that's not the case is it?
> > > 
> > > I don't understand why Mike and Stephen aren't helping!
> > 
> > I'll wait until tomorrow and if we haven't heard anything I'll make a
> > decision.
> 
> OK, thanks!
> 
> BTW, I don't have the time to review every single patch using ACPI
> or one of the PM frameworks.  If people who use them make mistakes,
> it is their burden to fix those mistakes when they show up in testing.
> 
> What's happening here is that Andy and Mika are taking the responsibility
> for fixing the new code if it turns out to be buggy and so it's their
> problem if it happens to be broken.
> 
> And you can still revert commits that introduce bugs as a last resort.

I'm fine with that in principle.  My issue here was that it looks
wrong to me.  I just don't know enough about the inner workings of the
CCF to be able to say that for sure, or to provide a suitable
alternative.  I think, probably the correct thing to do is to have an
accompanying clock driver, but who knows (I guess Stephen and Mike to,
but are seemingly unwilling to help).

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org â Open source software for ARM SoCs
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