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Message-ID: <1423855102.4182.63.camel@pengutronix.de>
Date: Fri, 13 Feb 2015 20:18:22 +0100
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc: Jonathan Corbet <corbet@....net>, Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Russell King <linux@....linux.org.uk>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
Linus Walleij <linus.walleij@...aro.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jslaby@...e.cz>, Arnd Bergmann <arnd@...db.de>,
Andrew Morton <akpm@...ux-foundation.org>,
"David S. Miller" <davem@...emloft.net>,
Mauro Carvalho Chehab <mchehab@....samsung.com>,
Joe Perches <joe@...ches.com>, Antti Palosaari <crope@....fi>,
Tejun Heo <tj@...nel.org>, Will Deacon <will.deacon@....com>,
Nikolay Borisov <Nikolay.Borisov@....com>,
Rusty Russell <rusty@...tcorp.com.au>,
Kees Cook <keescook@...omium.org>,
Michal Marek <mmarek@...e.cz>,
"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>,
"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
Linux-Arch <linux-arch@...r.kernel.org>,
"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>
Subject: Re: [PATCH 12/14] ARM: dts: Introduce STM32F429 MCU
Am Freitag, den 13.02.2015, 17:41 +0100 schrieb Maxime Coquelin:
> 2015-02-13 17:25 GMT+01:00 Philipp Zabel <p.zabel@...gutronix.de>:
> > Hi Maxime,
> >
> > Am Freitag, den 13.02.2015, 16:59 +0100 schrieb Maxime Coquelin:
> >> Hi Philipp,
> >>
> >> 2015-02-13 12:47 GMT+01:00 Philipp Zabel <p.zabel@...gutronix.de>:
> >> > Hi Maxime,
> >> >
> >> > Am Donnerstag, den 12.02.2015, 18:46 +0100 schrieb Maxime Coquelin:
> >> > [...]
> >> >> + soc {
> >> >> + reset_ahb1: reset@...23810 {
> >> >> + #reset-cells = <1>;
> >> >> + compatible = "st,stm32-reset";
> >> >> + reg = <0x40023810 0x4>;
> >> >> + };
> >> >> +
> >> >> + reset_ahb2: reset@...23814 {
> >> >> + #reset-cells = <1>;
> >> >> + compatible = "st,stm32-reset";
> >> >> + reg = <0x40023814 0x4>;
> >> >> + };
> >> >> +
> >> >> + reset_ahb3: reset@...23818 {
> >> >> + #reset-cells = <1>;
> >> >> + compatible = "st,stm32-reset";
> >> >> + reg = <0x40023818 0x4>;
> >> >> + };
> >> >> +
> >> >> + reset_apb1: reset@...23820 {
> >> >> + #reset-cells = <1>;
> >> >> + compatible = "st,stm32-reset";
> >> >> + reg = <0x40023820 0x4>;
> >> >> + };
> >> >> +
> >> >> + reset_apb2: reset@...23824 {
> >> >> + #reset-cells = <1>;
> >> >> + compatible = "st,stm32-reset";
> >> >> + reg = <0x40023824 0x4>;
> >> >> + };
> >> >
> >> > These are mostly consecutive, single registers. I wonder if these are
> >> > part of the same IP block and thus should be grouped together into the
> >> > same reset controller node?
> >>
> >> What I could to is to have two instances. One for AHB and one for APB domain.
> >> Doing this, I will have one instance per domain, and only consecutive registers.
> >> Is it fine for you?
> >
> > Looking at
> > http://www.st.com/web/en/resource/technical/document/reference_manual/DM00031020.pdf
> > Table 34 (RCC register map and reset values), I'd say there is a single
> > "Reset and Clock Control" device at 0x40023800 - 0x40023884:
> >
> > soc {
> > rcc: rcc@...23800 {
> > #clock-cells = <1>;
> > #reset-cells = <1>;
> > compatible = "st,stm32-rcc";
> > reg = <0x40023800 0x84>;
> > };
> >
> > ...
> >
> > If you really want to describe the reset controller parts (offsets +0x10
> > to +0x24) in a separate node, I won't argue against it too long,
> > although this is a somewhat arbitrary decision.
> >
> > In any case, the whole register at offset +0x1c is reserved, so there is
> > no reason to split the reset controller. It is ok to have unused ranges
> > as is already the case with reserved bits inside the used registers.
>
> Ok. I understand your point.
> But it will be more difficult at usage, because the node referencing
> the fourth reset bit of apb2 register will have to pass 164 as
> parameter.
> It is error prone IMHO.
>
> Other solution would be to add some defines for each reset line in the
> DT-Bindings, as we do today for STi platform.
> But it is giving an unneeded constraint between DT and reset trees.
That is a bit unfortunate, but providing the named constants in
include/dt-bindings/reset/ makes for a much better readable device tree,
so I'd prefer that solution, even if it means having to coordinate pull
requests.
regards
Philipp
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