linux-kernel - RE: [PATCH v2] i2c: tegra: Add delay before reset the controller

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Message-ID: <7A0BFCFE3DA5CD47B0FB7984326F201A13689D36EE@BGMAIL01.nvidia.com>
Date:	Fri, 10 Feb 2012 14:50:22 +0530
From:	Alok Chauhan <alokc@...dia.com>
To:	Alok Chauhan <alokc@...dia.com>, Ben Dooks <ben-i2c@...ff.org>
CC:	"khali@...ux-fr.org" <khali@...ux-fr.org>,
	"ben-linux@...ff.org" <ben-linux@...ff.org>,
	Stephen Warren <swarren@...dia.com>,
	"olof@...om.net" <olof@...om.net>,
	"bones@...retlab.ca" <bones@...retlab.ca>,
	"paul.gortmaker@...driver.com" <paul.gortmaker@...driver.com>,
	"dgreid@...gle.com" <dgreid@...gle.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] i2c: tegra: Add delay before reset the controller

> On Mon, Dec 26, 2011 at 04:44:41PM +0530, Alok Chauhan wrote:
>> 
> +	/*
> +	 * In NACK error condition resetting of I2C controller happens
> +	 * before STOP condition is properly completed by I2C controller,
> +	 * so wait for 2 clock cycle to complete STOP condition.
> +	 */
> +	if (i2c_dev->msg_err == I2C_ERR_NO_ACK)
> +		udelay(DIV_ROUND_UP(2 * 1000000, i2c_dev->bus_clk_rate));
> +

>Is a delay here good, would it be better to sleep so that some other process can gain cpu time?
>>We mostly used 100 khz i2c clock frequency and delay in that case will be 20 usec. Would it be ok to sleep for such a smaller time? Won't it increase any other overhead?

Please let me know if sleep is better option here instead of waiting.

Thanks
Alok

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