i2c-algo-bit.c

linux 下的i2c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 Ky鰏ti M鋖kki <[e-mail]> and even
   Frodo Looijaard <[e-mail]> */

/* $Id: i2c-algo-bit.c,v 1.30 2001/07/29 02:44:25 mds Exp $ */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/version.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/ioport.h>
#include <linux/errno.h>
#include <linux/sched.h>

#include <linux/i2c.h>
#include <linux/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 */

/* debugging - slow down transfer to have a look at the data .. 	*/
/* I use this with two leds&resistors, each one connected to sda,scl 	*/
/* respectively. This makes sure that the algorithm works. Some chips   */
/* might not like this, as they have an internal timeout of some mils	*/
/*
#define SLO_IO      jif=jiffies;while(time_before_eq(jiffies, jif+i2c_table[minor].veryslow))\
                        if (need_resched) schedule();
*/


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

#ifdef SLO_IO
	int jif;
#endif

/* module parameters:
 */
static int i2c_debug;
static int bit_test;	/* see if the line-setting functions work	*/
static int bit_scan;	/* have a look at what's hanging 'round		*/

/* --- 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);
#ifdef SLO_IO
	SLO_IO
#endif
}

/*
 * 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=jiffies;

	setscl(adap,1);

	udelay(adap->udelay);

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

 	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. 
 		 */
		setscl(adap,1);
		if (time_after_eq(jiffies, start+adap->timeout)) {
			return -ETIMEDOUT;
		}
		if (current->need_resched)
			schedule();
	}
	DEBSTAT(printk("needed %ld jiffies\n", jiffies-start));
#ifdef SLO_IO
	SLO_IO
#endif
	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);
	setscl(adap,1);
	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)

 * [e-mail]: an instruction to disable any timeconsuming interrupt
   here except the heart beat of timer2 should be added before setsda(adap, sb).
   because when interrupt occurs during
   scl is set high, the interrupt service routine is served and may take long,
   after the interrupt returns, sda could be sampled by the device(slave)
   more than once, and this cause error problem.
*/
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 */
	DEB2(printk(" i2c_outb:%2.2X\n",c&0xff));
	for ( i=7 ; i>=0 ; i-- ) {
		sb = c & ( 1 << i );
		setsda(adap,sb);
		udelay(adap->udelay);
		DEBPROTO(printk("%d",sb!=0));
		if (sclhi(adap)<0) { /* timed out */
			sdahi(adap); /* we don't want to block the net */
			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 */
		return -ETIMEDOUT;
	};
	/* read ack: SDA should be pulled down by slave */
	ack=getsda(adap);	/* ack: sda is pulled low ->success.	 */
	DEB2(printk(" i2c_outb: getsda() =  0x%2.2x\n", ~ack ));

	DEBPROTO( printk("[%2.2x]",c&0xff) );
	DEBPROTO(if (0==ack){ printk(" A ");} else printk(" 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 */
	DEB2(printk("i2c_inb.\n"));

	sdahi(adap);
	for (i=0;i<8;i++) {
		if (sclhi(adap)<0) { /* timeout */
			return -ETIMEDOUT;
		};
		indata *= 2;
		if ( getsda(adap) ) 
			indata |= 0x01;
		scllo(adap);
	}
	/* assert: scl is low */
	DEBPROTO(printk(" %2.2x", 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;
	sda=getsda(adap);
	if (adap->getscl==NULL) {
		printk("i2c-algo-bit.o: Warning: Adapter can't read from clock line - skipping test.\n");
		return 0;		
	}
	scl=getscl(adap);
	printk("i2c-algo-bit.o: Adapter: %s scl: %d  sda: %d -- testing...\n",
	       name,getscl(adap),getsda(adap));
	if (!scl || !sda ) {
		printk("i2c-algo-bit.o: %s seems to be busy.\n",name);
		goto bailout;
	}
	sdalo(adap);
	printk("i2c-algo-bit.o:1 scl: %d  sda: %d \n",getscl(adap),
	       getsda(adap));
	if ( 0 != getsda(adap) ) {
		printk("i2c-algo-bit.o: %s SDA stuck high!\n",name);
		sdahi(adap);
		goto bailout;
	}
	if ( 0 == getscl(adap) ) {
		printk("i2c-algo-bit.o: %s SCL unexpected low while pulling SDA low!\n",
			name);
		goto bailout;
	}		
	sdahi(adap);
	printk("i2c-algo-bit.o:2 scl: %d  sda: %d \n",getscl(adap),
	       getsda(adap));
	if ( 0 == getsda(adap) ) {
		printk("i2c-algo-bit.o: %s SDA stuck low!\n",name);
		sdahi(adap);
		goto bailout;
	}
	if ( 0 == getscl(adap) ) {
		printk("i2c-algo-bit.o: %s SCL unexpected low while SDA high!\n",
		       name);
	goto bailout;
	}
	scllo(adap);
	printk("i2c-algo-bit.o:3 scl: %d  sda: %d \n",getscl(adap),
	       getsda(adap));
	if ( 0 != getscl(adap) ) {
		printk("i2c-algo-bit.o: %s SCL stuck high!\n",name);
		sclhi(adap);
		goto bailout;
	}
	if ( 0 == getsda(adap) ) {
		printk("i2c-algo-bit.o: %s SDA unexpected low while pulling SCL low!\n",
			name);
		goto bailout;
	}
	sclhi(adap);
	printk("i2c-algo-bit.o:4 scl: %d  sda: %d \n",getscl(adap),
	       getsda(adap));
	if ( 0 == getscl(adap) ) {
		printk("i2c-algo-bit.o: %s SCL stuck low!\n",name);
		sclhi(adap);
		goto bailout;
	}
	if ( 0 == getsda(adap) ) {
		printk("i2c-algo-bit.o: %s SDA unexpected low while SCL high!\n",
			name);
		goto bailout;
	}
	printk("i2c-algo-bit.o: %s passed test.\n",name);
	return 0;
bailout: