Re: [PATCH v3 03/16] mfd: mfd-core: match device tree node against reg property

[Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On Mon, 25 May 2020, Michael Walle wrote:
> Am 2020-05-15 12:28, schrieb Lee Jones:
> > On Thu, 30 Apr 2020, Michael Walle wrote:
> > 
> > > Hi Lee,
> > > 
> > > Am 2020-04-23 19:45, schrieb Michael Walle:
> > > > There might be multiple children with the device tree compatible, for
> > > > example if a MFD has multiple instances of the same function. In this
> > > > case only the first is matched and the other children get a wrong
> > > > of_node reference.
> > > > Add a new option to match also against the unit address of the child
> > > > node. Additonally, a new helper OF_MFD_CELL_REG is added.

[...]

> > > > diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
> > > > index d01d1299e49d..c2c0ad6b14f3 100644
> > > > --- a/include/linux/mfd/core.h
> > > > +++ b/include/linux/mfd/core.h
> > > > @@ -13,8 +13,11 @@
> > > >  #include <linux/platform_device.h>
> > > >
> > > >  #define MFD_RES_SIZE(arr) (sizeof(arr) / sizeof(struct resource))
> > > > +#define MFD_OF_REG_VALID	BIT(31)
> > 
> > What about 64bit platforms?
> 
> The idea was to have this as a logical number. I.e. for now you may only
> have one subdevice per unique compatible string. In fact, if you have a
> look at the ab8500.c, there are multiple "stericsson,ab8500-pwm"
> subdevices. But there is only one DT node for all three of it. I guess
> this works as long as you don't use phandles to reference the pwm node
> in the device tree. Or you don't want to use device tree properties
> per subdevice (for example the "timeout-sec" of a watchdog device).

This is not a good example, as the "stericsson,ab8500-pwm" is
legitimate.  Here we are registering 3 potential devices, but only
instantiating 1 of them.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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