linux-kernel - Re: [PATCH v3 05/15] dt-bindings: Document the STM32 reset bindings

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Message-ID: <1426236654.3083.19.camel@pengutronix.de>
Date:	Fri, 13 Mar 2015 09:50:54 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc:	u.kleine-koenig@...gutronix.de, afaerber@...e.de,
	geert@...ux-m68k.org, Rob Herring <robh+dt@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, stefan@...er.ch,
	pmeerw@...erw.net, pebolle@...cali.nl,
	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>,
	Russell King <linux@....linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.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>,
	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-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-gpio@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v3  05/15] dt-bindings: Document the STM32 reset bindings

Hi Maxime,

Am Donnerstag, den 12.03.2015, 22:55 +0100 schrieb Maxime Coquelin:
> From: Maxime Coquelin <mcoquelin.stm32@...il.com>
> 
> This adds documentation of device tree bindings for the
> STM32 reset controller.
> 
> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@...il.com>
> ---
>  .../devicetree/bindings/reset/st,stm32-rcc.txt     | 102 +++++++++++++++++++++
>  1 file changed, 102 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/reset/st,stm32-rcc.txt
> 
> diff --git a/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt b/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt
> new file mode 100644
> index 0000000..962f961
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/reset/st,stm32-rcc.txt
> @@ -0,0 +1,102 @@
> +STMicroelectronics STM32 Peripheral Reset Controller
> +====================================================
> +
> +The RCC IP is both a reset and a clock controller. This documentation only
> +document the reset part.
> +
> +Please also refer to reset.txt in this directory for common reset
> +controller binding usage.
> +
> +Required properties:
> +- compatible: Should be "st,stm32-rcc"
> +- reg: should be register base and length as documented in the
> +  datasheet
> +- #reset-cells: 1, see below
> +
> +example:
> +
> +rcc: reset@...23800 {
> +	#reset-cells = <1>;
> +	compatible = "st,stm32-rcc";
> +	reg = <0x40023800 0x400>;
> +};
> +
> +Specifying softreset control of devices
> +=======================================
> +
> +Device nodes should specify the reset channel required in their "resets"
> +property, containing a phandle to the reset device node and an index specifying
> +which channel to use.

Using a single value as index is ok, but it should be documented how
this corresponds to the register and bit offsets in the reference
manual.
Maybe add a comment that the index is in fact the register offset / 4 *
32 + bit offset in that register and that not all registers are
dedicated to the rest controller? Otherwise it is confusing (to me at
least) that the indices start at some arbitrary value.

> +example:
> +
> +	timer2 {
> +		resets			= <&rcc 256>;
> +	};
> +
> +List of indexes for STM32F429:

"List of valid indices", to point out that any other index is invalid?

> + - gpioa: 128

I had to look at the RM0090 Reference manual V8.0, Chapter 6, "Reset and
clock control for STM32F42xx and STM32F43xxx (RCC)" to see that the
reset registers indeed start at 0x10 (RCC_AHB1RSTR), ...

> + - gpiob: 129
> + - gpioc: 130
> + - gpiod: 131
> + - gpioe: 132
> + - gpiof: 133
> + - gpiog: 134
> + - gpioh: 135
> + - gpioi: 136
> + - gpioj: 137
> + - gpiok: 138
> + - crc: 140
> + - dma1: 149
> + - dma2: 150
> + - dma2d: 151
> + - ethmac: 153
> + - otghs: 157
> + - dcmi: 160
> + - cryp: 164
> + - hash: 165
> + - rng: 166
> + - otgfs: 167
> + - fmc: 192
> + - tim2: 256
> + - tim3: 257
> + - tim4: 258
> + - tim5: 259
> + - tim6: 260
> + - tim7: 261
> + - tim12: 262
> + - tim13: 263
> + - tim14: 264
> + - wwdg: 267
> + - spi2: 270
> + - spi3: 271
> + - uart2: 273
> + - uart3: 274
> + - uart4: 275
> + - uart5: 276
> + - i2c1: 277
> + - i2c2: 278
> + - i2c3: 279
> + - can1: 281
> + - can2: 282
> + - pwr: 284
> + - dac: 285
> + - uart7: 286
> + - uart8: 287
> + - tim1: 288
> + - tim8: 289
> + - usart1: 292
> + - usart6: 293
> + - adc: 296
> + - sdio: 299
> + - spi1: 300
> + - spi4: 301
> + - syscfg: 302
> + - tim9: 304
> + - tim10: 305
> + - tim11: 306
> + - spi5: 308
> + - spi6: 309
> + - sai1: 310
> + - ltdc: 31

That last one should say "ltdc: 314", right?

regards
Philipp

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