Message-ID: <547331F2.3000006@ti.com>
Date: Mon, 24 Nov 2014 15:26:10 +0200
From: Grygorii Strashko <grygorii.strashko@ti.com>
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To: =?windows-1252?Q?Uwe_Kleine-K=F6nig?= 
	<u.kleine-koenig@pengutronix.de>
CC: Wolfram Sang <wsa@the-dreams.de>, <linux-i2c@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Sekhar Nori <nsekhar@ti.com>,
        Kevin Hilman <khilman@deeprootsystems.com>,
        Santosh Shilimkar <ssantosh@kernel.org>,
        Murali Karicheri <m-karicheri2@ti.com>
Subject: Re: [4/5] i2c: davinci: use bus recovery infrastructure
References: <1416477788-5544-5-git-send-email-grygorii.strashko@ti.com> <20141121190744.GB4431@pengutronix.de> <546F9382.40102@ti.com> <20141123203634.GG4431@pengutronix.de>
In-Reply-To: <20141123203634.GG4431@pengutronix.de>
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Sender: linux-kernel-owner@vger.kernel.org

Hi Uwe,

On 11/23/2014 10:36 PM, Uwe Kleine-K?nig wrote:
> On Fri, Nov 21, 2014 at 09:33:22PM +0200, Grygorii Strashko wrote:
>> On 11/21/2014 09:07 PM, Uwe Kleine-K?nig wrote:
>>> On Thu, Nov 20, 2014 at 12:03:07PM +0200, Grygorii Strashko wrote:
>>> Just another general comment about the driver that doesn't influence the
>>> correctness of this patch: The i2c-davinci driver is quite quick to
>>> reset the bus. I wonder how often this reset triggers. Is the bus in
>>> question less "stable" than others?
>>
>> In comparison to ..? :)
> In comparison to other bus drivers in other SoCs. I know this might be
> hard to answer. I just wonder where the reason for this has to be
> located. Strange hardware? Software bug? Or is this SoC just operating
> with strange slaves more often than others?

Davinci driver does reset in two cases:
- when I2C transaction isn't completed due to timeout (no irq received)
- when BB is detected
both cases are reasonable, because in 1st case HW state is undefined
in 2d case - Davinci I2C supports only master mode and if BB detected
we need perform some recovery procedure.

Also, this patch doesn't introduce functional changes - it's just code
reworking intended to reuse I2C bus recovery infrastructure

i2c-omap.c - OMAP I2C driver does mostly the same now.
i2c-tegra.c - seems, It will do reset even frequently.
i2c-imx.c - if understand right, it will reinitialize I2C controller 
before each transfer, because it enables/disables I2C clocks.
... 

So, what i can say here is just "In comparison to ..?" :)

regards,
-grygorii
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