linux-kernel - RE: [PATCH v6 1/2] i2c: imx: add DMA support for freescale i2c driver

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Date:	Thu, 7 Aug 2014 10:01:05 +0000
From:	"fugang.duan@...escale.com" <fugang.duan@...escale.com>
To:	Yao Yuan <yao.yuan@...escale.com>,
	"wsa@...-dreams.de" <wsa@...-dreams.de>,
	"marex@...x.de" <marex@...x.de>
CC:	"LW@...O-electronics.de" <LW@...O-electronics.de>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"Frank.Li@...escale.com" <Frank.Li@...escale.com>
Subject: RE: [PATCH v6 1/2] i2c: imx: add DMA support for freescale i2c driver

From: Yuan Yao-B46683 Data: Thursday, August 07, 2014 4:05 PM
>To: Duan Fugang-B38611; wsa@...-dreams.de; marex@...x.de
>Cc: LW@...O-electronics.de; mark.rutland@....com; shawn.guo@...aro.org;
>linux-kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
>i2c@...r.kernel.org; Li Frank-B20596
>Subject: RE: [PATCH v6 1/2] i2c: imx: add DMA support for freescale i2c
>driver
>
>Hi Fugang,
>
>> >> >+	/* Waiting for Transfer complete. */
>> >> >+	while (timeout--) {
>> >> >+		temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
>> >> >+		if (temp & I2SR_ICF)
>> >> >+			break;
>> >> >+		udelay(10);
>> >> >+	}
>> >> Whether there have better method like interrupt to avoid dead wait
>> >> here until timeout ?
>> >
>> >Can you give me more suggestion? We have discussed it with our team,
>> >It seems the short query wait is necessary.
>> >
>> At least, you can use schdule_timeout() instead of udelay() ?
>
>In fact, the waiting time normally is less than 10-50us, but the minimum
>time interval for schdule_timeout() is 1 jiffies.
>So maybe schdule_timeout() is not very necessary?
>
Oh, if the waiting time is 10 ~ 50us, you can use usleep_range(10, 50).
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