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

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Date:	Thu, 21 May 2015 22:10:35 +0200
From:	Maxime Coquelin <mcoquelin.stm32@...il.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Andreas Färber <afaerber@...e.de>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Rob Herring <robh+dt@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Stefan Agner <stefan@...er.ch>,
	Peter Meerwald <pmeerw@...erw.net>,
	Paul Bolle <pebolle@...cali.nl>,
	Peter Hurley <peter@...leysoftware.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Joe Perches <joe@...ches.com>,
	Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
	Lee Jones <lee.jones@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Nikolay Borisov <Nikolay.Borisov@....com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Kees Cook <keescook@...omium.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Nicolae Rosia <nicolae.rosia@...il.com>,
	Kamil Lulko <rev13@...pl>
Subject: Re: [PATCH v8 14/16] ARM: dts: Introduce STM32F429 MCU

2015-05-21 20:51 GMT+02:00 Maxime Ripard <maxime.ripard@...e-electrons.com>:
> On Wed, May 20, 2015 at 06:17:34PM +0200, Maxime Coquelin wrote:
>> Hi Arnd, Philipp,
>>
>> 2015-05-13 21:11 GMT+02:00 Arnd Bergmann <arnd@...db.de>:
>> > Ideally the binding should follow closely what is documented
>> > in the data sheet.
>> >
>>
>> Daniel and myself would like your opinion about this binding:
>>
>> rcc: rcc@...23800 {
>>     #reset-cells = <1>;
>>     #clock-cells = <2>;
>>     compatible = "st,stm32-rcc";
>>     reg = <0x40023800 0x10>, <0x40023810 0x20>, <0x40023830 0x20>;
>>     reg-names = "clock-cfg", "reset", "clock-gates";
>> };
>>
>> It would solve a problem Daniel is facing due to conflicting mem
>> region when clock and reset drivers are enabled, as both would reserve
>> the same region.
>>
>> Also, it would make the reset driver very generic.
>> Doing that, we could even create a generic-reset.c driver that would
>> be used by STM32 and Sunxi (at least).
>> 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 lack a bit of context here, but I'd be very happy to use a generic
> driver. As a matter of fact, the sunxi reset driver is already pretty
> much there (not that it's very difficult to do).

Ok, good. The two drivers are almost the same, so squashing to a
generic one would be trivial.

>
> The only thing we did that stands out a bit is that we actually need
> the reset driver much earlier than the default probe, since some of
> our timers are maintained in reset. We have some code to do just that
> already, we just need have something similar to be on board.

We have the same problem on stm32, as just discussed with Andreas [0].
I decided to patch the bootloader to deassert timers reset, after
discussions with Rob Herring and Arnd.

Moving to a common driver, stm32 could use the same early init method
to initiliaze reset before timers.

Regards,
Maxime

[0]: http://marc.info/?l=linux-arm-kernel&m=143223846802405&w=2#0
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