/*
 * Copyright (c) 1994 Gordon W. Ross
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *	$Id: eeprom.c,v 1.1 1994/09/20 16:35:44 gwr Exp $
 */

/*
 * Access functions for the EEPROM (Electrically Eraseable PROM)
 * The main reason for the existence of this module is to
 * handle the painful task of updating the EEPROM contents.
 * After a write, it must not be touched for 10 milliseconds.
 * (See the Sun-3 Architecture Manual sec. 5.9)
 */

#include <sys/param.h>
#include <sys/conf.h>
#include <sys/buf.h>
#include <sys/systm.h>
#include <sys/malloc.h>

#include <machine/obio.h>
#include <machine/eeprom.h>

#define HZ 100

static int ee_update(caddr_t buf, int off, int cnt);

static char *eeprom_va;
static int ee_busy, ee_want;

void eeprom_init()
{
	eeprom_va = obio_find_mapping(OBIO_EEPROM, OBIO_EEPROM_SIZE);
}

static int ee_take()	/* Take the lock. */
{
	int error = 0;
	while (ee_busy) {
		ee_want = 1;
		error = tsleep(&ee_busy, PZERO | PCATCH, "eeprom", 0);
		ee_want = 0;
		if (error)	/* interrupted */
			goto out;
	}
	ee_busy = 1;
 out:
	return error;
}

static void ee_give()	/* Give the lock. */
{
	ee_busy = 0;
	if (ee_want) {
		ee_want = 0;
		wakeup(&ee_busy);
	}
}

int eeprom_uio(struct uio *uio)
{
	int error;
	int off;	/* NOT off_t */
	u_int cnt;
	caddr_t va;
	caddr_t buf = (caddr_t)0;

	off = uio->uio_offset;
	if (off >= OBIO_EEPROM_SIZE)
		return (EFAULT);

	cnt = uio->uio_resid;
	if (cnt > (OBIO_EEPROM_SIZE - off))
		cnt = (OBIO_EEPROM_SIZE - off);

	if ((error = ee_take()) != 0)
		return (error);

	if (eeprom_va == NULL) {
		error = ENXIO;
		goto out;
	}

	va = eeprom_va;
	if (uio->uio_rw != UIO_READ) {
		/* Write requires a temporary buffer. */
		buf = malloc(OBIO_EEPROM_SIZE, M_DEVBUF, M_WAITOK);
		if (!buf) {
			error = EAGAIN;
			goto out;
		}
		va = buf;
	}

	if ((error = uiomove(va + off, (int)cnt, uio)) != 0)
		goto out;

	if (uio->uio_rw != UIO_READ)
		error = ee_update(buf, off, cnt);

 out:
	if (buf)
		free(buf, M_DEVBUF);
	ee_give();
	return (error);
}

/*
 * Update the EEPROM from the passed buf.
 */
static int ee_update(char *buf, int off, int cnt)
{
	volatile char *ep;
	char *bp;

	if (eeprom_va == NULL)
		return (ENXIO);

	ep = eeprom_va + off;
	bp = buf + off;

	while (cnt > 0) {
		/*
		 * DO NOT WRITE IT UNLESS WE HAVE TO because the
		 * EEPROM has a limited number of write cycles.
		 * After some number of writes it just fails!
		 */
		if (*ep != *bp) {
			*ep  = *bp;
			/*
			 * We have written the EEPROM, so now we must
			 * sleep for at least 10 milliseconds while
			 * holding the lock to prevent all access to
			 * the EEPROM while it recovers.
			 */
			(void)tsleep(eeprom_va, PZERO-1, "eeprom", HZ/50);
		}
		/* Make sure the write worked. */
		if (*ep != *bp)
			return (EIO);
		ep++;
		bp++;
		cnt--;
	}
}

/*
 * Read a byte out of the EEPROM.  This is called from
 * things like the zs driver very early to find out
 * which device should be used as the console.
 */
int ee_get_byte(int off, int canwait)
{
	int c = -1;
	if ((off < 0) || (off >= OBIO_EEPROM_SIZE))
		goto out;
	if (eeprom_va == NULL)
		goto out;

	if (canwait) {
		if (ee_take())
			goto out;
	} else {
		if (ee_busy)
			goto out;
	}

	c = eeprom_va[off] & 0xFF;

	if (canwait)
		ee_give();
 out:
	return c;
}