Re: [PATCH v8 1/2] mfd: add atmel-hlcdc driver

[Thierry Reding <thierry.reding@gmail.com>]

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On Tue, Oct 07, 2014 at 01:41:12PM +0200, Boris Brezillon wrote:
> On Tue, 7 Oct 2014 12:38:14 +0100
> Lee Jones <lee.jones@linaro.org> wrote:
> 
> > On Tue, 07 Oct 2014, Thierry Reding wrote:
> > 
> > > On Tue, Oct 07, 2014 at 11:17:43AM +0100, Lee Jones wrote:
> > > > On Tue, 07 Oct 2014, Thierry Reding wrote:
> > > > 
> > > > > On Tue, Oct 07, 2014 at 10:59:32AM +0100, Lee Jones wrote:
> > > > > > On Tue, 07 Oct 2014, Thierry Reding wrote:
> > > > > > 
> > > > > > > On Tue, Oct 07, 2014 at 10:44:27AM +0100, Lee Jones wrote:
> > > > > > > > On Mon, 06 Oct 2014, Boris Brezillon wrote:
> > > > > > > > 
> > > > > > > > > The HLCDC IP available on some Atmel SoCs (i.e. at91sam9n12, at91sam9x5
> > > > > > > > > family or sama5d3 family) exposes 2 subdevices:
> > > > > > > > > - a display controller (controlled by a DRM driver)
> > > > > > > > > - a PWM chip
> > > > > > > > > 
> > > > > > > > > The MFD device provides a regmap and several clocks (those connected
> > > > > > > > > to this hardware block) to its subdevices.
> > > > > > > > > 
> > > > > > > > > This way concurrent accesses to the iomem range are handled by the regmap
> > > > > > > > > framework, and each subdevice can safely access HLCDC registers.
> > > > > > > > > 
> > > > > > > > > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > > > > > > > > Acked-by: Lee Jones <lee.jones@linaro.org>
> > > > > > > > > Tested-by: Anthony Harivel <anthony.harivel@emtrion.de>
> > > > > > > > > Tested-by: Ludovic Desroches <ludovic.desroches@atmel.com>
> > > > > > > > > ---
> > > > > > > > >  drivers/mfd/Kconfig             |   6 ++
> > > > > > > > >  drivers/mfd/Makefile            |   1 +
> > > > > > > > >  drivers/mfd/atmel-hlcdc.c       | 122 ++++++++++++++++++++++++++++++++++++++++
> > > > > > > > >  include/linux/mfd/atmel-hlcdc.h |  85 ++++++++++++++++++++++++++++
> > > > > > > > >  4 files changed, 214 insertions(+)
> > > > > > > > >  create mode 100644 drivers/mfd/atmel-hlcdc.c
> > > > > > > > >  create mode 100644 include/linux/mfd/atmel-hlcdc.h
> > > > > > > > 
> > > > > > > > Applied for v3.19.
> > > > > > > 
> > > > > > > Will you provide a stable branch that I can pull into the PWM tree?
> > > > > > 
> > > > > > I hadn't planned on it.  What do you need that for?
> > > > > 
> > > > > Because the PWM driver depends on this series. But if you prefer you
> > > > > could also take the PWM driver through your tree.
> > > > 
> > > > Probably better to deal with that via Kconfig.
> > > 
> > > Do you have any suggestions? The PWM driver currently selects the
> > > MFD_ATMEL_HLCDC symbol, which as I understand will cause a Kconfig error
> > > if the latter isn't defined.
> > 
> > s/select/depends on/ for the desired effect.
> > 
> 
> Don't forget the atmel-hlcdc.h header file which is referenced by both
> the DRM and the PWM drivers.

The depends on will prevent the PWM driver from being built until MFD
becomes available, so the missing header file shouldn't be a problem.

That said, Nicolas Ferre (Cc'ing) at some point requested this to become
a select (or at least for the DRM driver, but I guess the same applies
to PWM) on the grounds that a depends on will make it more difficult to
enable the driver.

So we have two options here: 1) turn the select into a depends on here
and allow the dependency to be resolved that way, or 2) solve the
dependency by making sure the MFD part is merged first (either by
pulling the MFD tree into the PWM and DRM trees or waiting for a full
cycle for the MFD changes to land).

I don't mind either way.

Thierry

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