i2c-algo-bit.c

I2C总线LINUX驱动程序

/* ------------------------------------------------------------------------- */
/* 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]>, Ky鰏ti M鋖kki
   <[e-mail]> and Jean Delvare <[e-mail]> */

/* $Id: i2c-algo-bit.c,v 1.54 2005/11/05 12:44:36 khali Exp $ */

#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 "i2c.h"
#include "i2c-algo-bit.h"


/* ----- global defines ----------------------------------------------- */
#define DEB(x) if (i2c_debug>=1) x;
#define DEB2(x) if (i2c_debug>=2) x;
#define DEBSTAT(x) if (i2c_debug>=3) x; /* print several statistical values*/
#define DEBPROTO(x) if (i2c_debug>=9) { x; }
 	/* debug the protocol by showing transferred bits */


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

/* module parameters:
 */
static int i2c_debug;
static int bit_test;	/* see if the line-setting functions work	*/

/* --- 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);
}

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

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

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

	setscl(adap,1);

	/* Not all adapters have scl sense line... */
	if (adap->getscl == NULL ) {
		udelay(adap->udelay);
		return 0;
	}

	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;
		}
		if (current->need_resched)
			schedule();
	}
	DEBSTAT(printk(KERN_DEBUG "needed %ld jiffies\n", jiffies-start));
	udelay(adap->udelay);
	return 0;
} 


/* --- other auxiliary functions --------------------------------------	*/
static void i2c_start(struct i2c_algo_bit_data *adap) 
{
	/* assert: scl, sda are high */
	DEBPROTO(printk("S "));
	sdalo(adap);
	scllo(adap);
}

static void i2c_repstart(struct i2c_algo_bit_data *adap) 
{
	/* scl, sda may not be high */
	DEBPROTO(printk(" Sr "));
	setsda(adap,1);
	sclhi(adap);
	udelay(adap->udelay);
	
	sdalo(adap);
	scllo(adap);
}


static void i2c_stop(struct i2c_algo_bit_data *adap) 
{
	DEBPROTO(printk("P\n"));
	/* assert: scl is low */
	sdalo(adap);
	sclhi(adap); 
	sdahi(adap);
}



/* 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, 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 & ( 1 << i );
		setsda(adap,sb);
		udelay(adap->udelay);
		DEBPROTO(printk(KERN_DEBUG "%d",sb!=0));
		if (sclhi(adap)<0) { /* timed out */
			sdahi(adap); /* we don't want to block the net */
			DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at bit #%d\n", c&0xff, i));
			return -ETIMEDOUT;
		};
		/* do arbitration here: 
		 * if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
		 */
		setscl(adap, 0 );
		udelay(adap->udelay);
	}
	sdahi(adap);
	if (sclhi(adap)<0){ /* timeout */
		DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at ack\n", c&0xff));
		return -ETIMEDOUT;
	};
	/* read ack: SDA should be pulled down by slave */
	ack=getsda(adap);	/* ack: sda is pulled low ->success.	 */
	DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x , getsda() = %d\n", c & 0xff, ack));

	DEBPROTO( printk(KERN_DEBUG "[%2.2x]",c&0xff) );
	DEBPROTO(if (0==ack){ printk(KERN_DEBUG " A ");} else printk(KERN_DEBUG " NA ") );
	scllo(adap);
	return 0==ack;		/* return 1 if device acked	 */
	/* 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 */
			DEB2(printk(KERN_DEBUG " i2c_inb: timeout at bit #%d\n", 7-i));
			return -ETIMEDOUT;
		};
		indata *= 2;
		if ( getsda(adap) ) 
			indata |= 0x01;
		scllo(adap);
	}
	/* assert: scl is low */
	DEB2(printk(KERN_DEBUG "i2c_inb: 0x%02x\n", indata & 0xff));

	DEBPROTO(printk(KERN_DEBUG " 0x%02x", indata & 0xff));
	return (int) (indata & 0xff);
}

/*
 * 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)
		printk(KERN_INFO "i2c-algo-bit.o: Testing SDA only, "
			"SCL is not readable.\n");

	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	printk(KERN_DEBUG "i2c-algo-bit.o: (0) scl=%d, sda=%d\n",scl,sda);
	if (!scl || !sda ) {
		printk(KERN_WARNING "i2c-algo-bit.o: %s seems to be busy.\n", name);
		goto bailout;
	}

	sdalo(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	printk(KERN_DEBUG "i2c-algo-bit.o: (1) scl=%d, sda=%d\n",scl,sda);
	if ( 0 != sda ) {
		printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck high!\n");
		goto bailout;
	}
	if ( 0 == scl ) {
		printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
			"while pulling SDA low!\n");
		goto bailout;
	}		

	sdahi(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	printk(KERN_DEBUG "i2c-algo-bit.o: (2) scl=%d, sda=%d\n",scl,sda);
	if ( 0 == sda ) {
		printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck low!\n");
		goto bailout;
	}
	if ( 0 == scl ) {
		printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
			"while pulling SDA high!\n");
		goto bailout;
	}

	scllo(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?0:getscl(adap));
	printk(KERN_DEBUG "i2c-algo-bit.o: (3) scl=%d, sda=%d\n",scl,sda);
	if ( 0 != scl ) {
		printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck high!\n");
		goto bailout;
	}
	if ( 0 == sda ) {
		printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
			"while pulling SCL low!\n");
		goto bailout;
	}
	
	sclhi(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	printk(KERN_DEBUG "i2c-algo-bit.o: (4) scl=%d, sda=%d\n",scl,sda);
	if ( 0 == scl ) {
		printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck low!\n");
		goto bailout;
	}
	if ( 0 == sda ) {
		printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
			"while pulling SCL high!\n");
		goto bailout;
	}
	printk(KERN_INFO "i2c-algo-bit.o: %s passed test.\n",name);
	return 0;
bailout:
	sdahi(adap);
	sclhi(adap);
	return -ENODEV;