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

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Message-ID: <20200608184507.GC4106@dell>
Date:   Mon, 8 Jun 2020 19:45:07 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Michael Walle <michael@...le.cc>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>, Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-pwm@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 03/16] mfd: mfd-core: match device tree node against
 reg property

On Mon, 08 Jun 2020, Michael Walle wrote:

> Am 2020-06-08 16:24, schrieb Lee Jones:
> > 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/plataorm_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.
> 
> Mh?
> 
> static const struct mfd_cell ab8500_devs[] = {
> ..
>        OF_MFD_CELL("ab8500-pwm",
>                     NULL, NULL, 0, 1, "stericsson,ab8500-pwm"),
>         OF_MFD_CELL("ab8500-pwm",
>                     NULL, NULL, 0, 2, "stericsson,ab8500-pwm"),
>         OF_MFD_CELL("ab8500-pwm",
>                     NULL, NULL, 0, 3, "stericsson,ab8500-pwm"),
> ..
> }
> 
> And in pwm-ab8500.c there are three offsets based on the pdev->id.
> 
> Am I missing something here?

Scrap what I said above.

For some reason I had of_platform_populate() in my head.

This will register and enumerate 3 devices.

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