linux-kernel - Re: [PATCH-v3 07/11] i2c: pxa: enable/disable i2c module across msg xfer

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Message-ID: <55A3EA23.8070009@linaro.org>
Date:	Mon, 13 Jul 2015 22:11:07 +0530
From:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
To:	Wolfram Sang <wsa@...-dreams.de>
CC:	linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	robert.jarzmik@...e.fr, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, robh+dt@...nel.org,
	Yi Zhang <yizhang@...vell.com>
Subject: Re: [PATCH-v3 07/11] i2c: pxa: enable/disable i2c module across msg
 xfer



On Friday 10 July 2015 01:54 PM, Wolfram Sang wrote:
> On Tue, Jul 07, 2015 at 12:54:51AM +0530, Vaibhav Hiremath wrote:
>> From: Yi Zhang <yizhang@...vell.com>
>>
>> Enable i2c module/unit before transmission and disable when it finishes.
>>
>> why?
>> It's because the i2c bus may be distrubed if the slave device,
>> typically a touch, powers on.
>>
>> As we do not want to break slave mode support, this patch introduces
>> DT property to control disable of the I2C module after xfer in master mode
>> of operation.
>>
>> i2c-disable-after-xfer : If set, driver will disable I2C module after msg xfer
>
> Hmm, I am not sure this property fits into the "describing hardware"
> category. And we can't make the below behaviour default, because the
> udelay(100) will cause quite some latency.
>
>>

Sorry for delayed response,
I thought I responded to this, but when I was preparing for V4,
realized it that I did not :)

Yes, I agree that, this doesn't look like HW description. But I could
not find any other mechanism to handle this.
And also during V1 discussion, I did not get any objection to this
approach.


Thanks,
Vaibhav
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