Re: [PATCH v8 14/16] ARM: dts: Introduce STM32F429 MCU

[Maxime Ripard <maxime.ripard@free-electrons.com>]

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Hi Philipp,

On Fri, May 22, 2015 at 12:07:11PM +0200, Philipp Zabel wrote:
> Am Freitag, den 22.05.2015, 11:18 +0200 schrieb Maxime Ripard:
> > On Fri, May 22, 2015 at 11:06:28AM +0200, Philipp Zabel wrote:
> > > > In the probe function, it would check the number of reg resources.
> > > > If a single resource is passed, it would take it, else it would look
> > > > the one named "reset".
> > > > The driver and bindings would be the same for the two families, and
> > > > the bindings would be backward compatible with sunxi ones.
> > > > 
> > > > Philip, Arnd, what do you think?
> > > 
> > > I'm not a fan of describing the register layout in the device tree as
> > > detailed as the sunxi bindings do. I'd prefer the reg property to
> > > describe the device's register address space with one entry per
> > > contiguous block of registers.
> > 
> > That's exactly what we do.
> 
> Sorry, what I mean is 'as detailed as reusing the sunxi bindings for
> stm32xx here would do'. I don't know enough about the Allwinner register
> layouts to form an opinion.
> 
> The STM32F427xx/STM32F429xx manual, Table 13. "STM32F427xx and
> STM32F429xx register boundary addresses" contains this entry:
>     Bus    Boundary address       Peripheral
>     AHB1   0x40023800-0x400238bf  RCC
> 
> And that's how I'd expect it to be described by the device tree:
> 
>     rcc: rcc@40023800 {
>         compatible = "st,stm32-rcc";
>         reg = <0x40023800 0xc0>;
>     };

It's pretty much what we do already. The thing is that our reset
controllers are intertwined with our clock ones, so our reset
controllers are usually taking only a few registers, and we can't use
more than that since we have clocks in the registers around.

> Instead of "reg = <0x40023810 0x20>" for the resets. Where in the
> address range the reset, clock gate and clock configuration registers
> reside could be derived from the compatible value.

I agree on that, and if a generic solution was to be made like this,
we could definitely use it.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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