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

From: Maxime Coquelin <mcoquelin.stm32@gmail.com>
To: "Maxime Ripard" <maxime.ripard@free-electrons.com>,
	"Andreas Färber" <afaerber@suse.de>
Cc: "Arnd Bergmann" <arnd@arndb.de>,
	"Philipp Zabel" <p.zabel@pengutronix.de>,
	"Daniel Thompson" <daniel.thompson@linaro.org>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Geert Uytterhoeven" <geert@linux-m68k.org>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Stefan Agner" <stefan@agner.ch>,
	"Peter Meerwald" <pmeerw@pmeerw.net>,
	"Paul Bolle" <pebolle@tiscali.nl>,
	"Peter Hurley" <peter@hurleysoftware.com>,
	"Andy Shevchenko" <andy.shevchenko@gmail.com>,
	"Chanwoo Choi" <cw00.choi@samsung.com>,
	"Russell King" <linux@arm.linux.org.uk>,
	"Daniel Lezcano" <daniel.lezcano@linaro.org>,
	"Joe Perches" <joe@perches.com>,
	"Vladimir Zapolskiy" <vladimir_zapolskiy@mentor.com>,
	"Lee Jones" <lee.jones@linaro.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Ian Campbell" <ijc+devicetree@hellion.org.uk>,
	"Kumar Gala" <galak@codeaurora.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Jiri Slaby" <jslaby@suse.cz>,
	"Nikolay Borisov" <Nikolay.Borisov@arm.com>,
	"Rusty Russell" <rusty@rustcorp.com.au>,
	"Kees Cook" <keescook@chromium.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"Nicolae Rosia" <nicolae.rosia@gmail.com>,
	"Kamil Lulko" <rev13@wp.pl>
Subject: Re: [PATCH v8 14/16] ARM: dts: Introduce STM32F429 MCU
Date: Thu, 21 May 2015 22:10:35 +0200	[thread overview]
Message-ID: <CALszF6BuvTf86k6S5UEYZs-DJSTehy=+Csb3c6jxMU90MN05zw@mail.gmail.com> (raw)
In-Reply-To: <20150521185122.GD8557@lukather>

2015-05-21 20:51 GMT+02:00 Maxime Ripard <maxime.ripard@free-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@arndb.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@40023800 {
>>     #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