Re: [PATCH 1/3] i2c-mv64xxx: Add I2C Transaction Generator support

From: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
To: Gregory CLEMENT
	<gregory.clement-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
Cc: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>,
	linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Jason Cooper <jason-NLaQJdtUoK4Be96aLqz0jA@public.gmane.org>,
	Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>,
	Thomas Petazzoni
	<thomas.petazzoni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>,
	Lior Amsalem <alior-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	Yehuda Yitschak <yehuday-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	Ike Pan <ike.pan-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
	Piotr Ziecik <kosmo-nYOzD4b6Jr9Wk0Htik3J/w@public.gmane.org>,
	Tawfik Bayouk <tawfik-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	Nicolas Pitre <nico-vtqb6HGKxmzR7s880joybQ@public.gmane.org>,
	Dan Frazier
	<dann.frazier-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
	Chris Van Hoof <vanhoof-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
	David Marlin <dmarlin-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Eran Ben-Avi <benavi-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	Nadav Haklai <nadavh-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	Maen Suleiman <maen-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	Shadi Ammouri <shadi-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	Ezequiel Garcia
	<ezequiel.garcia-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>,
	Jon Masters <jcm-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Leif Lindholm <leif.lindholm-5wv7dgnIgG8@public.gmane.org>,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	Sebastian Hesselbarth
	<sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 1/3] i2c-mv64xxx: Add I2C Transaction Generator support
Date: Tue, 6 Aug 2013 18:21:51 +0200	[thread overview]
Message-ID: <20130806162151.GB2911@lukather> (raw)
In-Reply-To: <5200E684.5080003-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>

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On Tue, Aug 06, 2013 at 02:05:24PM +0200, Gregory CLEMENT wrote:
> On 16/07/2013 10:05, Maxime Ripard wrote:
> > Hi Gregory,
> > 
> > On Mon, Jul 15, 2013 at 04:24:36PM +0200, Gregory CLEMENT wrote:
> >> The I2C Transaction Generator offloads CPU from managing I2C transfer step by step.
> >> 
> >> This feature is currently only available on Armada XP, so usage of this mechanism is activated through device tree.
> >> 
> >> Based on the work of Piotr Ziecik and rewrote to use the new way of handling multiples i2c messages.
> >> 
> >> Signed-off-by: Piotr Ziecik <kosmo-nYOzD4b6Jr9Wk0Htik3J/w@public.gmane.org> Signed-off-by: Gregory CLEMENT <gregory.clement-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> --- drivers/i2c/busses/i2c-mv64xxx.c | 207
> >> ++++++++++++++++++++++++++++++++++++--- 1 file changed, 196 insertions(+), 11 deletions(-)
> > 
> > [...]
> > 
> >> +	/* +	 * For controllers embedded in new SoCs activate the +	 * Transaction Generator support. +	 */ +	if (of_device_is_compatible(np, "marvell,mv78230-i2c")) +
> >> drv_data->offload_enabled = true; +
> > 
> > Do you have a reason for not adding it to the match table? I mean, you will introduce a new compatible here, but if that compatible is used alone, won't probe the driver? That doesn't
> > seem very right to me.
> 
> But we shouldn't use it alone: we should always use:
> compatible = "marvell,mv78230-i2c", "marvell,mv64xxx-i2c";
> 
> From my point of view using  "marvell,mv78230-i2c" alone is an error.

Why is that? If the I2C controller is a new IP with additional features,
it should have a full compatible of its own, doesn't it?

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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