linux-kernel - Re: [5/7] i2c-designware: enable/disable the controller properly

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Message-ID: <20130409092836.GG21818@intel.com>
Date:	Tue, 9 Apr 2013 12:28:36 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	ben-linux@...ff.org, Jean Delvare <khali@...ux-fr.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Christian Ruppert <christian.ruppert@...lis.com>
Subject: Re: [5/7] i2c-designware: enable/disable the controller properly

On Tue, Apr 09, 2013 at 11:09:14AM +0200, Wolfram Sang wrote:
> 
> > +static void __i2c_dw_enable(struct dw_i2c_dev *dev, bool enable)
> > +{
> > +	int timeout = 100;
> > +
> > +	do {
> > +		dw_writel(dev, enable, DW_IC_ENABLE);
> > +		if ((dw_readl(dev, DW_IC_ENABLE_STATUS) & 1) == enable)
> > +			return;
> > +
> > +		usleep_range(25, 250);
> 
> This would wait 25ms max. Is there a timeout value specified in the docs?

The datasheet says something like:

	1. Define a timer interval (t_i2c_poll) equal 10 times the highest
	signaling period. For 400kHz this is 25us.

	2. Define max timeout parameter, MAX_T_POLL_COUNT, such that if any
	repeated operation exeeds this maximum, an error is reported.

In this case I have:

	t_i2c_poll = 25 (to 250 us)
	MAX_T_POLL_COUNT = 100

> > +	} while (timeout-- > 0);
> 
> while (timeout--)?

OK, thanks.
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