Re: [PATCH 3/7] gpio: mvebu: Add limited PWM support

[Lee Jones <lee.jones@xxxxxxxxxx>]

On Mon, 19 Jan 2015, Thierry Reding wrote:

> On Sun, Jan 18, 2015 at 10:04:38AM +0000, Lee Jones wrote:
> > On Thu, 15 Jan 2015, Linus Walleij wrote:
> > 
> > > On Tue, Jan 13, 2015 at 3:42 AM, Andrew Lunn <andrew@xxxxxxx> wrote:
> > > 
> > > > So i thought about this some more. What would an MFD based solution
> > > > look like?
> > > >
> > > > First issue is backwards compatibility. There are currently around 90
> > > > .dts files using this gpio driver. I could imagine a few of these
> > > > being changed to make use of an MFD based driver to make us of the new
> > > > features, but the rest expect backwards compatibility.
> > > 
> > > Good point.
> > > 
> > > > I think the only sensible way to achieve this is that the gpio driver
> > > > keeps its existing binding.
> > > 
> > > Yup.
> > > 
> > > > This does not really describe the hardware. The hardware is more like:
> > > >
> > > >         gpio: gpio {
> > > >                 compatible = "marvell,orion-gpio";
> > > >                 reg = <0xd0018100 0x40>;
> > > >                 ngpios = <32>;
> > > >                 gio-controller;
> > > >                 #gpio-cells = <2>;
> > > >                 interrupt-controller;
> > > >                 #interrupt-cells = <2>;
> > > >                 interrupts = <16>, <17>, <18>, <19>;
> > > >                 clocks = <&coreclk 0>;
> > > >
> > > >                 pwm: pwm {
> > > >                         compatible = "marvell,armada-pwm";
> > > >                         reg = <0xd00181c0 0x08>;
> > > >                         #pwm-cells = <2>;
> > > >                         clocks = <&coreclk 0>;
> > > >                 };
> > > >         };
> 
> I think you technically need an (empty) ranges property in the gpio node
> so that the address can be properly translated.
> 
> > > >
> > > > but i don't think MFD supports that sort of structure?
> > > 
> > > No it would have to be some custom DT code in the GPIO driver
> > > spawning the PWM platform device.
> > 
> > of_platform_populate()?
> 
> Huh? I was under the impression that mfd_add_devices() would already
> deal with this situation? Isn't that what's parsed based on the cells
> parameter?

There was talk of this _not_ being an MFD device.  I was providing an
alternative way to get this device registered.

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