linux-kernel - Re: [PATCH v2 5/5] i2c: davinci: use ICPFUNC to toggle I2C as gpio for bus recovery

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Date:	Tue, 07 Jul 2015 15:37:49 +0200
From:	Jan Lübbe <jlu@...gutronix.de>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, Wolfram Sang <wsa@...-dreams.de>,
	Sekhar Nori <nsekhar@...com>, linux-i2c@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Mike Looijmans <milo-software@...rs.sourceforge.net>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Santosh Shilimkar <ssantosh@...nel.org>,
	Murali Karicheri <m-karicheri2@...com>,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 5/5] i2c: davinci: use ICPFUNC to toggle I2C as gpio
 for bus recovery

On Mi, 2014-11-26 at 19:05 +0200, Grygorii Strashko wrote:
> On 11/26/2014 06:04 PM, Uwe Kleine-König wrote:
> > On Wed, Nov 26, 2014 at 03:59:53PM +0200, Grygorii Strashko wrote:
> >> Having a board where the I2C bus locks up occasionally made it clear
> >> that the bus recovery in the i2c-davinci driver will only work on
> >> some boards, because on regular boards, this will only toggle GPIO
> >> lines that aren't muxed to the actual pins.
> >>
> >> The I2C controller on SoCs like da850 (and da830), Keystone 2 has the
> >> built-in capability to bit-bang its lines by using the ICPFUNC registers
> >> of the i2c controller.
> >> Implement the suggested procedure by toggling SCL and checking SDA using
> >> the ICPFUNC registers of the I2C controller when present. Allow platforms
> >> to indicate the presence of the ICPFUNC registers with a has_pfunc platform
> >> data flag and add optional DT property "ti,has-pfunc" to indicate
> >> the same in DT.
> > On what does it depend if this pfunc stuff works or not? Only the SoC,
> > or also on some board specific properties?
> 
> SoC / set of SoCs. Also, similar feature is supported by OMAP and AM335x/AM437x SoCs
> using I2C_SYSTEST register.
> 
> > Given the former using the
> > compatible string to detect its availability would be better. (In this
> > case also sorry, didn't consider this case when requesting the property
> > in the last round.)

I only stumbled across this after it was merged, with the additional
ti,has-pfunc property instead of using the compatible string (which
would be better for a soc-dependent feature). Can we still fix this?

Regards,
Jan
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