linux-kernel - Re: [PATCH v3 4/5] i2c: davinci: use bus recovery infrastructure

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Date:	Fri, 3 Apr 2015 22:18:46 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	"Grygorii.Strashko@...aro.org" <grygorii.strashko@...aro.org>
Cc:	Sekhar Nori <nsekhar@...com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, linux-i2c@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Kevin Hilman <khilman@...prootsystems.com>,
	Santosh Shilimkar <ssantosh@...nel.org>,
	Murali Karicheri <m-karicheri2@...com>,
	Alexander Sverdlin <alexander.sverdlin@...ia.com>
Subject: Re: [PATCH v3 4/5] i2c: davinci: use bus recovery infrastructure


> > The I2C specs say in 3.1.16 that the recovery procedure should be used
> > when SDA is stuck low. So, I do wonder if we should apply the recovery
> > after a timeout. Stuck SDA might be one reason for timeout, but there
> > may be others...
> 
> This is ancient code. And regarding your question -
> Might be it would be reasonable to add call of
> i2c_davinci_wait_bus_not_busy() at the end of i2c_davinci_xfer()?
> This way we will wait for Bus Free before performing recovery.

That might be an improvement, but the generic question still remains:
Is a timeout a reason for recovery? SDA stuck low is one reason for a
timeout. I have problems making up my mind here between being pragmatic
and being in accordance with the specs.

> Of course,  i2c_davinci_wait_bus_not_busy() has to be fixed first
> as proposed by Alexander Sverdlin here:
>  https://patchwork.ozlabs.org/patch/448994/. 

Okay, good that you said it. So I'll give his patch series priority over
this one.


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