linux-kernel - Re: Fwd: [PATCH v7] i2c: exynos5: add High Speed I2C controller driver

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Date:	Thu, 2 May 2013 13:27:21 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Naveen Krishna Ch <naveenkrishna.ch@...il.com>
Cc:	linux-i2c@...r.kernel.org,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>, linux-kernel@...r.kernel.org,
	grant.likely@...retlab.ca, devicetree-discuss@...ts.ozlabs.org,
	sjg@...omium.org, Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Naveen Krishna Chatradhi <ch.naveen@...sung.com>
Subject: Re: Fwd: [PATCH v7] i2c: exynos5: add High Speed I2C controller
 driver

Hi,

> >> +  - Samsung GPIO variant (deprecated):
> >> +    - gpios: The order of the gpios should be the following: <SDA, SCL>.
> >> +      The gpio specifier depends on the gpio controller.
> >
> > Huh? Why should we support a deprecated method with a new driver?
> >

This was left unanswered. I am curious.

> >> +Optional properties:
> >> +  - samsung,hs-mode: Mode of operation, High speed or Fast speed mode. If not
> >> +    specified, default value is 0.
> >> +  - samsung,hs-clock-freq: Desired operating frequency in Hz of the bus.
> >> +    If not specified, the default value in Hz is 100000.
> >> +  - samsung,fs-clock-freq: Desired operarting frequency in Hz of the bus.
> >> +    If not specified, the default value in Hz is 100000.
> >
> > NACK! We have a generic binding for defining the bus speed. And
> > shouldn't hs-mode be set depending on the bus speed?

Please use "clock-frequency" here, like other drivers do.

> >> +     /* In auto mode the length of xfer cannot be 0 */
> >> +     if (i2c->msg->len == 0)
> >> +             i2c_auto_conf |= 0x1;
> >
> > So you send some byte then? Why not reject the message?
> This is to support the probing the devices (i2cdetect cases)

No! This is not a proper SMBUS_QUICK if you send a byte! If it doesn't
work without sending data, then your device does not support it. This is
not uncommon. Please check the smbus specs if you are unsure.

> >> +     i2c->regs = of_iomap(np, 0);
> >
> > devm_ioremap_resource()
> This was a comment from Thomas on v1.
> https://lkml.org/lkml/2012/11/27/264
> 
> Kindly, suggest me which one is more optimal in this case.

"Optimal" is difficult here, but devm_* has momentum and I prefer
consistency.

> Thanks for your valuable time and comments

You're welcome! Thanks for the submission.

   Wolfram

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