i2c-keywest.c

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/*
    i2c Support for Apple Keywest I2C Bus Controller

    Copyright (c) 2001 Benjamin Herrenschmidt <[e-mail]>

    Original work by
    
    Copyright (c) 2000 Philip Edelbrock <[e-mail]>

    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.

    Changes:

    2001/12/13 BenH	New implementation
    2001/12/15 BenH	Add support for "byte" and "quick"
                        transfers. Add i2c_xfer routine.
    2003/09/21 BenH	Rework state machine with Paulus help
    2004/01/21 BenH	Merge in Greg KH changes, polled mode is back
    2004/02/05 BenH	Merge 64 bits fixes from the g5 ppc64 tree

    My understanding of the various modes supported by keywest are:

     - Dumb mode : not implemented, probably direct tweaking of lines
     - Standard mode : simple i2c transaction of type
         S Addr R/W A Data A Data ... T
     - Standard sub mode : combined 8 bit subaddr write with data read
         S Addr R/W A SubAddr A Data A Data ... T
     - Combined mode : Subaddress and Data sequences appended with no stop
         S Addr R/W A SubAddr S Addr R/W A Data A Data ... T

    Currently, this driver uses only Standard mode for i2c xfer, and
    smbus byte & quick transfers ; and uses StandardSub mode for
    other smbus transfers instead of combined as we need that for the
    sound driver to be happy
*/

#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/ioport.h>
#include <linux/pci.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/timer.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/interrupt.h>

#include <asm/io.h>
#include <asm/prom.h>
#include <asm/machdep.h>
#include <asm/pmac_feature.h>
#include <asm/pmac_low_i2c.h>

#include "i2c-keywest.h"

#undef POLLED_MODE

/* Some debug macros */
#define WRONG_STATE(name) do {\
		pr_debug("KW: wrong state. Got %s, state: %s (isr: %02x)\n", \
			 name, __kw_state_names[iface->state], isr);	\
	} while(0)

#ifdef DEBUG
static const char *__kw_state_names[] = {
	"state_idle",
	"state_addr",
	"state_read",
	"state_write",
	"state_stop",
	"state_dead"
};
#endif /* DEBUG */

MODULE_AUTHOR("Benjamin Herrenschmidt <[e-mail]>");
MODULE_DESCRIPTION("I2C driver for Apple's Keywest");
MODULE_LICENSE("GPL");
MODULE_PARM(probe, "i");

static int probe = 0;

#ifdef POLLED_MODE
/* Don't schedule, the g5 fan controller is too
 * timing sensitive
 */
static u8
wait_interrupt(struct keywest_iface* iface)
{
	int i;
	u8 isr;
	
	for (i = 0; i < 200000; i++) {
		isr = read_reg(reg_isr) & KW_I2C_IRQ_MASK;
		if (isr != 0)
			return isr;
		udelay(10);
	}
	return isr;
}
#endif /* POLLED_MODE */

static void
do_stop(struct keywest_iface* iface, int result)
{
	write_reg(reg_control, KW_I2C_CTL_STOP);
	iface->state = state_stop;
	iface->result = result;
}

/* Main state machine for standard & standard sub mode */
static void
handle_interrupt(struct keywest_iface *iface, u8 isr)
{
	int ack;
	
	if (isr == 0) {
		if (iface->state != state_stop) {
			pr_debug("KW: Timeout !\n");
			do_stop(iface, -EIO);
		}
		if (iface->state == state_stop) {
			ack = read_reg(reg_status);
			if (!(ack & KW_I2C_STAT_BUSY)) {
				iface->state = state_idle;
				write_reg(reg_ier, 0x00);
#ifndef POLLED_MODE
				complete(&iface->complete);
#endif /* POLLED_MODE */
			}
		}
		return;
	}

	if (isr & KW_I2C_IRQ_ADDR) {
		ack = read_reg(reg_status);
		if (iface->state != state_addr) {
			write_reg(reg_isr, KW_I2C_IRQ_ADDR);
			WRONG_STATE("KW_I2C_IRQ_ADDR"); 
			do_stop(iface, -EIO);
			return;
		}
		if ((ack & KW_I2C_STAT_LAST_AAK) == 0) {
			iface->state = state_stop;		     
			iface->result = -ENODEV;
			pr_debug("KW: NAK on address\n");
		} else {
			/* Handle rw "quick" mode */
			if (iface->datalen == 0) {
				do_stop(iface, 0);
			} else if (iface->read_write == I2C_SMBUS_READ) {
				iface->state = state_read;
				if (iface->datalen > 1)
					write_reg(reg_control, KW_I2C_CTL_AAK);
			} else {
				iface->state = state_write;
				write_reg(reg_data, *(iface->data++));
				iface->datalen--;
			}
		}
		write_reg(reg_isr, KW_I2C_IRQ_ADDR);
	}

	if (isr & KW_I2C_IRQ_DATA) {
		if (iface->state == state_read) {
			*(iface->data++) = read_reg(reg_data);
			write_reg(reg_isr, KW_I2C_IRQ_DATA);
			iface->datalen--;
			if (iface->datalen == 0)
				iface->state = state_stop;
			else if (iface->datalen == 1)
				write_reg(reg_control, 0);
		} else if (iface->state == state_write) {
			/* Check ack status */
			ack = read_reg(reg_status);
			if ((ack & KW_I2C_STAT_LAST_AAK) == 0) {
				pr_debug("KW: nack on data write (%x): %x\n",
				    iface->data[-1], ack);
				do_stop(iface, -EIO);
			} else if (iface->datalen) {
				write_reg(reg_data, *(iface->data++));
				iface->datalen--;
			} else {
				write_reg(reg_control, KW_I2C_CTL_STOP);
				iface->state = state_stop;
				iface->result = 0;
			}
			write_reg(reg_isr, KW_I2C_IRQ_DATA);
		} else {
			write_reg(reg_isr, KW_I2C_IRQ_DATA);
			WRONG_STATE("KW_I2C_IRQ_DATA"); 
			if (iface->state != state_stop)
				do_stop(iface, -EIO);
		}
	}

	if (isr & KW_I2C_IRQ_STOP) {
		write_reg(reg_isr, KW_I2C_IRQ_STOP);
		if (iface->state != state_stop) {
			WRONG_STATE("KW_I2C_IRQ_STOP");
			iface->result = -EIO;
		}
		iface->state = state_idle;
		write_reg(reg_ier, 0x00);
#ifndef POLLED_MODE
		complete(&iface->complete);
#endif /* POLLED_MODE */			
	}

	if (isr & KW_I2C_IRQ_START)
		write_reg(reg_isr, KW_I2C_IRQ_START);
}

#ifndef POLLED_MODE

/* Interrupt handler */
static irqreturn_t
keywest_irq(int irq, void *dev_id, struct pt_regs *regs)
{
	struct keywest_iface *iface = (struct keywest_iface *)dev_id;
	unsigned long flags;

	spin_lock_irqsave(&iface->lock, flags);
	del_timer(&iface->timeout_timer);
	handle_interrupt(iface, read_reg(reg_isr));
	if (iface->state != state_idle) {
		iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
		add_timer(&iface->timeout_timer);
	}
	spin_unlock_irqrestore(&iface->lock, flags);
	return IRQ_HANDLED;
}

static void
keywest_timeout(unsigned long data)
{
	struct keywest_iface *iface = (struct keywest_iface *)data;
	unsigned long flags;

	pr_debug("timeout !\n");
	spin_lock_irqsave(&iface->lock, flags);
	handle_interrupt(iface, read_reg(reg_isr));
	if (iface->state != state_idle) {
		iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
		add_timer(&iface->timeout_timer);
	}
	spin_unlock_irqrestore(&iface->lock, flags);
}

#endif /* POLLED_MODE */

/*
 * SMBUS-type transfer entrypoint
 */
static s32
keywest_smbus_xfer(	struct i2c_adapter*	adap,
			u16			addr,
			unsigned short		flags,
			char			read_write,
			u8			command,
			int			size,
			union i2c_smbus_data*	data)
{
	struct keywest_chan* chan = i2c_get_adapdata(adap);
	struct keywest_iface* iface = chan->iface;
	int len;
	u8* buffer;
	u16 cur_word;
	int rc = 0;

	if (iface->state == state_dead)
		return -ENXIO;
		
	/* Prepare datas & select mode */
	iface->cur_mode &= ~KW_I2C_MODE_MODE_MASK;
	switch (size) {
        case I2C_SMBUS_QUICK:
	    	len = 0;
	    	buffer = NULL;
	    	iface->cur_mode |= KW_I2C_MODE_STANDARD;
	    	break;
        case I2C_SMBUS_BYTE:
	    	len = 1;
	    	buffer = &data->byte;
	    	iface->cur_mode |= KW_I2C_MODE_STANDARD;
	    	break;
        case I2C_SMBUS_BYTE_DATA:
	    	len = 1;
	    	buffer = &data->byte;
	    	iface->cur_mode |= KW_I2C_MODE_STANDARDSUB;
	    	break;
        case I2C_SMBUS_WORD_DATA:
	    	len = 2;
	    	cur_word = cpu_to_le16(data->word);
	    	buffer = (u8 *)&cur_word;
	    	iface->cur_mode |= KW_I2C_MODE_STANDARDSUB;
		break;
        case I2C_SMBUS_BLOCK_DATA:
	    	len = data->block[0];
	    	buffer = &data->block[1];
	    	iface->cur_mode |= KW_I2C_MODE_STANDARDSUB;
		break;
        default:
	    	return -1;
	}

	/* Turn a standardsub read into a combined mode access */
 	if (read_write == I2C_SMBUS_READ
 	    && (iface->cur_mode & KW_I2C_MODE_MODE_MASK) == KW_I2C_MODE_STANDARDSUB) {
 		iface->cur_mode &= ~KW_I2C_MODE_MODE_MASK;
 		iface->cur_mode |= KW_I2C_MODE_COMBINED;
 	}

	/* Original driver had this limitation */
	if (len > 32)
		len = 32;

	if (pmac_low_i2c_lock(iface->node))
		return -ENXIO;

	pr_debug("chan: %d, addr: 0x%x, transfer len: %d, read: %d\n",
		chan->chan_no, addr, len, read_write == I2C_SMBUS_READ);

	iface->data = buffer;
	iface->datalen = len;
	iface->state = state_addr;
	iface->result = 0;
	iface->read_write = read_write;
	
	/* Setup channel & clear pending irqs */
	write_reg(reg_isr, read_reg(reg_isr));
	write_reg(reg_mode, iface->cur_mode | (chan->chan_no << 4));
	write_reg(reg_status, 0);

	/* Set up address and r/w bit */
	write_reg(reg_addr,
		(addr << 1) | ((read_write == I2C_SMBUS_READ) ? 0x01 : 0x00));

	/* Set up the sub address */
	if ((iface->cur_mode & KW_I2C_MODE_MODE_MASK) == KW_I2C_MODE_STANDARDSUB
	    || (iface->cur_mode & KW_I2C_MODE_MODE_MASK) == KW_I2C_MODE_COMBINED)
		write_reg(reg_subaddr, command);

#ifndef POLLED_MODE
	/* Arm timeout */
	iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
	add_timer(&iface->timeout_timer);
#endif

	/* Start sending address & enable interrupt*/
	write_reg(reg_control, KW_I2C_CTL_XADDR);
	write_reg(reg_ier, KW_I2C_IRQ_MASK);

#ifdef POLLED_MODE
	pr_debug("using polled mode...\n");
	/* State machine, to turn into an interrupt handler */
	while(iface->state != state_idle) {
		unsigned long flags;

		u8 isr = wait_interrupt(iface);
		spin_lock_irqsave(&iface->lock, flags);
		handle_interrupt(iface, isr);
		spin_unlock_irqrestore(&iface->lock, flags);
	}
#else /* POLLED_MODE */
	pr_debug("using interrupt mode...\n");
	wait_for_completion(&iface->complete);	
#endif /* POLLED_MODE */