Date:	Wed, 13 May 2015 13:58:05 +0100
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Arnd Bergmann <arnd@...db.de>
CC:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Andreas Färber <afaerber@...e.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Rob Herring <robh+dt@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	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>,
	Jonathan Corbet <corbet@....net>,
	Pawel Moll <pawel.moll@....com>,
	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>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Mauro Carvalho Chehab <mchehab@....samsung.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>,
	Nicolae Rosia <nicolae.rosia@...il.com>,
	Kamil Lulko <rev13@...pl>
Subject: Re: [PATCH v8 14/16] ARM: dts: Introduce STM32F429 MCU

On 13/05/15 12:45, Maxime Coquelin wrote:
> 2015-05-12 23:21 GMT+02:00 Arnd Bergmann <arnd@...db.de>:
>> On Saturday 09 May 2015 09:53:56 Maxime Coquelin wrote:
>>> +#include  <dt-bindings/mfd/stm32f4-rcc.h>
>>> +
>>>
>>
>> Can you find a way to avoid this dependency?
>>
>> Maybe you can change the bindings so that the numbers you pass as
>> arguments to the reset and clock specifiers reflect the numbers that
>> the hardware use?
>
> If I understand correctly, you prefer the way I did in v7 [0]?
>
> I don't have a strong opinion on this. Either way is fine to me.
>
> I changed the bindings in the v8 after discussions with Daniel
> Thompson, who is implementing the clock driver part of the RCC IP.
>
> He proposed we used common defines, because each peripheral has a
> reset line and a clock gate.
> Both reset and clock are represented as a single bit, with only the
> base offset differing between clock and reset.
> You can have a look at chapter 6 of the reference manual [1] if you
> find some time.
>
> Having common defines between clocks and reset make sense to me, but I
> also understand your point of avoiding dependencies.
>
> Maybe I can revert back to v7 bindings for now, and then we can
> reconsider using common defines when Daniel will send the clock
> patches.
> Note that doing that won't break the DT binary compatibility, as the
> raw reset values, or the ones from defines are the same.
>
> Daniel, could you share an example of the bindings you would use for the clocks?

For the most cases, where there is a clock gate just before the 
peripheral it looks pretty much like the reset driver and I use the bit 
offset of the clock gating bit as the index.

However there are a couple of clocks without gating just before the 
clock reaches the peripheral:

1. A hard coded /8. I think this will have to be given a synthetic
    number.

2. Ungated dividers. For these I am using the bit offset of the LSB of
    the mux field.

So I think there is only one value that is completely unrelated to the 
hardware and will use a magic constant instead.

I had planned to macros similar to the STM32F4_AxB_RESET() family of 
macros in both clk driver and DT in order to reuse the bit layouts from 
dt-bindings/mfd/stm32f4-rcc.h .

Normal case would have looked like this:

		timer3: timer@...00000 {
			compatible = "st,stm32-timer";
			reg = <0x40000000 0x400>;
			interrupts = <28>;
			resets = <&rcc STM32F4_APB1_RESET(TIM3)>;
			clocks = <&rcc STM32F4_APB1_CLK(TIM3)>;
			status = "disabled";
		};

Without the macros it looks like this:

		timer3: timer@...00000 {
			compatible = "st,stm32-timer";
			reg = <0x40000000 0x400>;
			interrupts = <28>;
			resets = <&rcc 257>;
			clocks = <&rcc 513>;
			status = "disabled";
		};

However we could perhaps be more literate even if we don't use the macros?

		timer3: timer@...00000 {
			compatible = "st,stm32-timer";
			reg = <0x40000000 0x400>;
			interrupts = <28>;
			resets = <&rcc ((0x20*8) + 1)>;
			clocks = <&rcc ((0x40*8) + 1)>;
			status = "disabled";
		};


Daniel.


> Kind regards,
> Maxime
>
>>
>>          Arnd
>
> [0]: http://lkml.iu.edu/hypermail/linux/kernel/1504.3/04523.html
> [1]: http://www.st.com/web/en/resource/technical/document/reference_manual/DM00031020.pdf
>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists