i2c-algo-bit.c

linux 内核源代码

/* ------------------------------------------------------------------------- */
/* i2c-algo-bit.c i2c driver algorithms for bit-shift adapters		     */
/* ------------------------------------------------------------------------- */
/*   Copyright (C) 1995-2000 Simon G. Vogl

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.		     */
/* ------------------------------------------------------------------------- */

/* With some changes from Frodo Looijaard <[e-mail]>, Kyösti Mälkki
   <[e-mail]> and Jean Delvare <[e-mail]> */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>


/* ----- global defines ----------------------------------------------- */

#ifdef DEBUG
#define bit_dbg(level, dev, format, args...) \
	do { \
		if (i2c_debug >= level) \
			dev_dbg(dev, format, ##args); \
	} while (0)
#else
#define bit_dbg(level, dev, format, args...) \
	do {} while (0)
#endif /* DEBUG */

/* ----- global variables ---------------------------------------------	*/

static int bit_test;	/* see if the line-setting functions work	*/
module_param(bit_test, bool, 0);
MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");

#ifdef DEBUG
static int i2c_debug = 1;
module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(i2c_debug,
		 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
#endif

/* --- setting states on the bus with the right timing: ---------------	*/

#define setsda(adap,val) adap->setsda(adap->data, val)
#define setscl(adap,val) adap->setscl(adap->data, val)
#define getsda(adap) adap->getsda(adap->data)
#define getscl(adap) adap->getscl(adap->data)

static inline void sdalo(struct i2c_algo_bit_data *adap)
{
	setsda(adap,0);
	udelay((adap->udelay + 1) / 2);
}

static inline void sdahi(struct i2c_algo_bit_data *adap)
{
	setsda(adap,1);
	udelay((adap->udelay + 1) / 2);
}

static inline void scllo(struct i2c_algo_bit_data *adap)
{
	setscl(adap,0);
	udelay(adap->udelay / 2);
}

/*
 * Raise scl line, and do checking for delays. This is necessary for slower
 * devices.
 */
static int sclhi(struct i2c_algo_bit_data *adap)
{
	unsigned long start;

	setscl(adap,1);

	/* Not all adapters have scl sense line... */
	if (!adap->getscl)
		goto done;

	start=jiffies;
	while (! getscl(adap) ) {	
 		/* the hw knows how to read the clock line,
 		 * so we wait until it actually gets high.
 		 * This is safer as some chips may hold it low
 		 * while they are processing data internally. 
 		 */
		if (time_after_eq(jiffies, start+adap->timeout)) {
			return -ETIMEDOUT;
		}
		cond_resched();
	}
#ifdef DEBUG
	if (jiffies != start && i2c_debug >= 3)
		pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
			 "high\n", jiffies - start);
#endif

done:
	udelay(adap->udelay);
	return 0;
} 


/* --- other auxiliary functions --------------------------------------	*/
static void i2c_start(struct i2c_algo_bit_data *adap) 
{
	/* assert: scl, sda are high */
	setsda(adap, 0);
	udelay(adap->udelay);
	scllo(adap);
}

static void i2c_repstart(struct i2c_algo_bit_data *adap) 
{
	/* assert: scl is low */
	sdahi(adap);
	sclhi(adap);
	setsda(adap, 0);
	udelay(adap->udelay);
	scllo(adap);
}


static void i2c_stop(struct i2c_algo_bit_data *adap) 
{
	/* assert: scl is low */
	sdalo(adap);
	sclhi(adap); 
	setsda(adap, 1);
	udelay(adap->udelay);
}



/* send a byte without start cond., look for arbitration, 
   check ackn. from slave */
/* returns:
 * 1 if the device acknowledged
 * 0 if the device did not ack
 * -ETIMEDOUT if an error occurred (while raising the scl line)
 */
static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
{
	int i;
	int sb;
	int ack;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: scl is low */
	for ( i=7 ; i>=0 ; i-- ) {
		sb = (c >> i) & 1;
		setsda(adap,sb);
		udelay((adap->udelay + 1) / 2);
		if (sclhi(adap)<0) { /* timed out */
			bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
				"timeout at bit #%d\n", (int)c, i);
			return -ETIMEDOUT;
		};
		/* do arbitration here: 
		 * if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
		 */
		scllo(adap);
	}
	sdahi(adap);
	if (sclhi(adap)<0){ /* timeout */
		bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
			"timeout at ack\n", (int)c);
		return -ETIMEDOUT;
	};
	/* read ack: SDA should be pulled down by slave */
	ack = !getsda(adap);    /* ack: sda is pulled low -> success */
	bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
		ack ? "A" : "NA");

	scllo(adap);
	return ack;
	/* assert: scl is low (sda undef) */
}


static int i2c_inb(struct i2c_adapter *i2c_adap) 
{
	/* read byte via i2c port, without start/stop sequence	*/
	/* acknowledge is sent in i2c_read.			*/
	int i;
	unsigned char indata=0;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: scl is low */
	sdahi(adap);
	for (i=0;i<8;i++) {
		if (sclhi(adap)<0) { /* timeout */
			bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
				"#%d\n", 7 - i);
			return -ETIMEDOUT;
		};
		indata *= 2;
		if ( getsda(adap) ) 
			indata |= 0x01;
		setscl(adap, 0);
		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
	}
	/* assert: scl is low */
	return indata;
}

/*
 * Sanity check for the adapter hardware - check the reaction of
 * the bus lines only if it seems to be idle.
 */
static int test_bus(struct i2c_algo_bit_data *adap, char* name) {
	int scl,sda;

	if (adap->getscl==NULL)
		pr_info("%s: Testing SDA only, SCL is not readable\n", name);

	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	if (!scl || !sda ) {
		printk(KERN_WARNING "%s: bus seems to be busy\n", name);
		goto bailout;
	}

	sdalo(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	if ( 0 != sda ) {
		printk(KERN_WARNING "%s: SDA stuck high!\n", name);
		goto bailout;
	}
	if ( 0 == scl ) {
		printk(KERN_WARNING "%s: SCL unexpected low "
		       "while pulling SDA low!\n", name);
		goto bailout;
	}		

	sdahi(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	if ( 0 == sda ) {
		printk(KERN_WARNING "%s: SDA stuck low!\n", name);
		goto bailout;
	}
	if ( 0 == scl ) {
		printk(KERN_WARNING "%s: SCL unexpected low "
		       "while pulling SDA high!\n", name);
		goto bailout;
	}

	scllo(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?0:getscl(adap));
	if ( 0 != scl ) {
		printk(KERN_WARNING "%s: SCL stuck high!\n", name);
		goto bailout;
	}
	if ( 0 == sda ) {
		printk(KERN_WARNING "%s: SDA unexpected low "
		       "while pulling SCL low!\n", name);
		goto bailout;
	}
	
	sclhi(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	if ( 0 == scl ) {
		printk(KERN_WARNING "%s: SCL stuck low!\n", name);
		goto bailout;
	}
	if ( 0 == sda ) {
		printk(KERN_WARNING "%s: SDA unexpected low "
		       "while pulling SCL high!\n", name);
		goto bailout;
	}
	pr_info("%s: Test OK\n", name);
	return 0;
bailout:
	sdahi(adap);
	sclhi(adap);
	return -ENODEV;
}

/* ----- Utility functions
 */

/* try_address tries to contact a chip for a number of
 * times before it gives up.
 * return values:
 * 1 chip answered