i2c.c

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/*!***************************************************************************
*!
*! FILE NAME  : i2c.c
*!
*! DESCRIPTION: implements an interface for IIC/I2C, both directly from other
*!              kernel modules (i2c_writereg/readreg) and from userspace using
*!              ioctl()'s
*!
*! Nov 30 1998  Torbjorn Eliasson  Initial version.
*!              Bjorn Wesen        Elinux kernel version.
*! Jan 14 2000  Johan Adolfsson    Fixed PB shadow register stuff - 
*!                                 don't use PB_I2C if DS1302 uses same bits,
*!                                 use PB.
*| June 23 2003 Pieter Grimmerink  Added 'i2c_sendnack'. i2c_readreg now
*|                                 generates nack on last received byte, 
*|                                 instead of ack.
*|                                 i2c_getack changed data level while clock
*|                                 was high, causing DS75 to see  a stop condition
*|
*! $Log: i2c.c,v $
*! Revision 1.12  2003/06/23 14:43:47  oskarp
*! * i2c_sendnack is added.
*!   - i2c_readreg now generates nack on last received byte, instead of ack.
*!     i2c_getack changed data level while clock was high, causing DS75 to
*!     see a stop condition.
*!
*! Revision 1.11  2003/05/23 09:37:23  oskarp
*! * Made i2c_init() visible.
*!   - e.g. pcf856.c uses i2c_init().
*!
*! Revision 1.10  2003/04/01 14:12:06  starvik
*! Added loglevel for lots of printks
*!
*! Revision 1.9  2002/10/31 15:32:26  starvik
*! Update Port B register and shadow even when running with hardware support
*!   to avoid glitches when reading bits
*! Never set direction to out in i2c_inbyte
*! Removed incorrect clock togling at end of i2c_inbyte
*!
*! Revision 1.8  2002/08/13 06:31:53  starvik
*! Made SDA and SCL line configurable
*! Modified i2c_inbyte to work with PCF8563
*!
*! Revision 1.7  2001/04/04 13:11:36  markusl
*! Updated according to review remarks
*!
*! Revision 1.6  2001/03/19 12:43:00  markusl
*! Made some symbols unstatic (used by the eeprom driver)
*!
*! Revision 1.5  2001/02/27 13:52:48  bjornw
*! malloc.h -> slab.h
*!
*! Revision 1.4  2001/02/15 07:17:40  starvik
*! Corrected usage if port_pb_i2c_shadow
*!
*! Revision 1.3  2001/01/26 17:55:13  bjornw
*! * Made I2C_USES_PB_NOT_PB_I2C a CONFIG option instead of assigning it
*!   magically. Config.in needs to set it for the options that need it, like
*!   Dallas 1302 support. Actually, it should be default since it screws up
*!   the PB bits even if you don't use I2C..
*! * Include linux/config.h to get the above
*!
*! Revision 1.2  2001/01/18 15:49:30  bjornw
*! 2.4 port of I2C including some cleanups (untested of course)
*!
*! Revision 1.1  2001/01/18 15:35:25  bjornw
*! Verbatim copy of the Etrax i2c driver, 2.0 elinux version
*!
*!
*! ---------------------------------------------------------------------------
*!
*! (C) Copyright 1999-2002 Axis Communications AB, LUND, SWEDEN
*!
*!***************************************************************************/
/* $Id: i2c.c,v 1.12 2003/06/23 14:43:47 oskarp Exp $ */
/****************** INCLUDE FILES SECTION ***********************************/

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/config.h>

#include <asm/etraxi2c.h>

#include <asm/system.h>
#include <asm/svinto.h>
#include <asm/io.h>
#include <asm/delay.h>

#include "i2c.h"

/****************** I2C DEFINITION SECTION *************************/

#define D(x)

#define I2C_MAJOR 123  /* LOCAL/EXPERIMENTAL */
static const char i2c_name[] = "i2c";

#define CLOCK_LOW_TIME            8
#define CLOCK_HIGH_TIME           8
#define START_CONDITION_HOLD_TIME 8
#define STOP_CONDITION_HOLD_TIME  8
#define ENABLE_OUTPUT 0x01
#define ENABLE_INPUT 0x00
#define I2C_CLOCK_HIGH 1
#define I2C_CLOCK_LOW 0
#define I2C_DATA_HIGH 1
#define I2C_DATA_LOW 0

#if 0
/* TODO: fix this so the CONFIG_ETRAX_I2C_USES... is set in Config.in instead */
#if defined(CONFIG_DS1302) && (CONFIG_DS1302_SDABIT==0) && \
           (CONFIG_DS1302_SCLBIT == 1)
#define CONFIG_ETRAX_I2C_USES_PB_NOT_PB_I2C
#endif
#endif

#ifdef CONFIG_ETRAX_I2C_USES_PB_NOT_PB_I2C
/* Use PB and not PB_I2C */
#ifndef CONFIG_ETRAX_I2C_DATA_PORT
#define CONFIG_ETRAX_I2C_DATA_PORT 0
#endif
#ifndef CONFIG_ETRAX_I2C_CLK_PORT
#define CONFIG_ETRAX_I2C_CLK_PORT 1
#endif

#define SDABIT CONFIG_ETRAX_I2C_DATA_PORT
#define SCLBIT CONFIG_ETRAX_I2C_CLK_PORT
#define i2c_enable() 
#define i2c_disable() 

/* enable or disable output-enable, to select output or input on the i2c bus */

#define i2c_dir_out() \
  REG_SHADOW_SET(R_PORT_PB_DIR, port_pb_dir_shadow, SDABIT, 1)
#define i2c_dir_in()  \
  REG_SHADOW_SET(R_PORT_PB_DIR, port_pb_dir_shadow, SDABIT, 0)

/* control the i2c clock and data signals */

#define i2c_clk(x) \
  REG_SHADOW_SET(R_PORT_PB_DATA, port_pb_data_shadow, SCLBIT, x)
#define i2c_data(x) \
  REG_SHADOW_SET(R_PORT_PB_DATA, port_pb_data_shadow, SDABIT, x)

/* read a bit from the i2c interface */

#define i2c_getbit() (((*R_PORT_PB_READ & (1 << SDABIT))) >> SDABIT)

#else /* !CONFIG_ETRAX_I2C_USES_PB_NOT_PB_I2C */
/* enable or disable the i2c interface */

#define i2c_enable() *R_PORT_PB_I2C = (port_pb_i2c_shadow |= IO_MASK(R_PORT_PB_I2C, i2c_en))
#define i2c_disable() *R_PORT_PB_I2C = (port_pb_i2c_shadow &= ~IO_MASK(R_PORT_PB_I2C, i2c_en))

/* enable or disable output-enable, to select output or input on the i2c bus */

#define i2c_dir_out() \
	*R_PORT_PB_I2C = (port_pb_i2c_shadow &= ~IO_MASK(R_PORT_PB_I2C, i2c_oe_)); \
	REG_SHADOW_SET(R_PORT_PB_DIR, port_pb_dir_shadow, 0, 1); 
#define i2c_dir_in() \
	*R_PORT_PB_I2C = (port_pb_i2c_shadow |= IO_MASK(R_PORT_PB_I2C, i2c_oe_)); \
	REG_SHADOW_SET(R_PORT_PB_DIR, port_pb_dir_shadow, 0, 0);

/* control the i2c clock and data signals */

#define i2c_clk(x) \
	*R_PORT_PB_I2C = (port_pb_i2c_shadow = (port_pb_i2c_shadow & \
       ~IO_MASK(R_PORT_PB_I2C, i2c_clk)) | IO_FIELD(R_PORT_PB_I2C, i2c_clk, (x))); \
       REG_SHADOW_SET(R_PORT_PB_DATA, port_pb_data_shadow, 1, x);

#define i2c_data(x) \
	*R_PORT_PB_I2C = (port_pb_i2c_shadow = (port_pb_i2c_shadow & \
	   ~IO_MASK(R_PORT_PB_I2C, i2c_d)) | IO_FIELD(R_PORT_PB_I2C, i2c_d, (x))); \
	REG_SHADOW_SET(R_PORT_PB_DATA, port_pb_data_shadow, 0, x);

/* read a bit from the i2c interface */

#define i2c_getbit() (*R_PORT_PB_READ & 0x1)

#endif /* CONFIG_ETRAX_I2C_USES_PB_NOT_PB_I2C */

/* use the kernels delay routine */

#define i2c_delay(usecs) udelay(usecs)


/****************** FUNCTION DEFINITION SECTION *************************/


/* generate i2c start condition */

void
i2c_start(void)
{
	/*
	 * SCL=1 SDA=1
	 */
	i2c_dir_out();
	i2c_delay(CLOCK_HIGH_TIME/6);
	i2c_data(I2C_DATA_HIGH);
	i2c_clk(I2C_CLOCK_HIGH);
	i2c_delay(CLOCK_HIGH_TIME);
	/*
	 * SCL=1 SDA=0
	 */
	i2c_data(I2C_DATA_LOW);
	i2c_delay(START_CONDITION_HOLD_TIME);
	/*
	 * SCL=0 SDA=0
	 */
	i2c_clk(I2C_CLOCK_LOW);
	i2c_delay(CLOCK_LOW_TIME);
}

/* generate i2c stop condition */

void
i2c_stop(void)
{
	i2c_dir_out();

	/*
	 * SCL=0 SDA=0
	 */
	i2c_clk(I2C_CLOCK_LOW);
	i2c_data(I2C_DATA_LOW);
	i2c_delay(CLOCK_LOW_TIME*2);
	/*
	 * SCL=1 SDA=0
	 */
	i2c_clk(I2C_CLOCK_HIGH);
	i2c_delay(CLOCK_HIGH_TIME*2);
	/*
	 * SCL=1 SDA=1
	 */
	i2c_data(I2C_DATA_HIGH);
	i2c_delay(STOP_CONDITION_HOLD_TIME);

	i2c_dir_in();
}

/* write a byte to the i2c interface */

void
i2c_outbyte(unsigned char x)
{
	int i;

	i2c_dir_out();

	for (i = 0; i < 8; i++) {
		if (x & 0x80) {
			i2c_data(I2C_DATA_HIGH);
		} else {
			i2c_data(I2C_DATA_LOW);
		}
		
		i2c_delay(CLOCK_LOW_TIME/2);
		i2c_clk(I2C_CLOCK_HIGH);
		i2c_delay(CLOCK_HIGH_TIME);
		i2c_clk(I2C_CLOCK_LOW);
		i2c_delay(CLOCK_LOW_TIME/2);
		x <<= 1;
	}
	i2c_data(I2C_DATA_LOW);
	i2c_delay(CLOCK_LOW_TIME/2);

	/*
	 * enable input
	 */
	i2c_dir_in();
}

/* read a byte from the i2c interface */

unsigned char
i2c_inbyte(void)
{
	unsigned char aBitByte = 0;
	int i;

	/* Switch off I2C to get bit */
	i2c_disable();
	i2c_dir_in();
	i2c_delay(CLOCK_HIGH_TIME/2);

	/* Get bit */
	aBitByte |= i2c_getbit();

	/* Enable I2C */
	i2c_enable();
	i2c_delay(CLOCK_LOW_TIME/2);

	for (i = 1; i < 8; i++) {
		aBitByte <<= 1;
		/* Clock pulse */
		i2c_clk(I2C_CLOCK_HIGH);
		i2c_delay(CLOCK_HIGH_TIME);
		i2c_clk(I2C_CLOCK_LOW);
		i2c_delay(CLOCK_LOW_TIME);

		/* Switch off I2C to get bit */
		i2c_disable();
		i2c_dir_in();
		i2c_delay(CLOCK_HIGH_TIME/2);

		/* Get bit */
		aBitByte |= i2c_getbit();

		/* Enable I2C */
		i2c_enable();
		i2c_delay(CLOCK_LOW_TIME/2);
	}
	i2c_clk(I2C_CLOCK_HIGH);
	i2c_delay(CLOCK_HIGH_TIME);
	
	/*
	 * we leave the clock low, getbyte is usually followed
	 * by sendack/nack, they assume the clock to be low
	 */
	i2c_clk(I2C_CLOCK_LOW);
	return aBitByte;
}

/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_getack
*#
*# DESCRIPTION  : checks if ack was received from ic2
*#
*#--------------------------------------------------------------------------*/

int
i2c_getack(void)
{
	int ack = 1;
	/*
	 * enable output
	 */
	i2c_dir_out();
	/*
	 * Release data bus by setting
	 * data high
	 */
	i2c_data(I2C_DATA_HIGH);
	/*
	 * enable input
	 */
	i2c_dir_in();
	i2c_delay(CLOCK_HIGH_TIME/4);
	/*
	 * generate ACK clock pulse
	 */
	i2c_clk(I2C_CLOCK_HIGH);
	/*
	 * Use PORT PB instead of I2C
	 * for input. (I2C not working)
	 */
	i2c_clk(1);
	i2c_data(1);