/*
* at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
*
* Copyright (C) 2006 David Brownell
*
* 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.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/sched.h>
#include <linux/spi/spi.h>
#include <linux/spi/eeprom.h>
struct at25_data {
struct spi_device *spi;
struct mutex lock;
struct spi_eeprom chip;
struct bin_attribute bin;
unsigned addrlen;
};
#define AT25_WREN 0x06 /* latch the write enable */
#define AT25_WRDI 0x04 /* reset the write enable */
#define AT25_RDSR 0x05 /* read status register */
#define AT25_WRSR 0x01 /* write status register */
#define AT25_READ 0x03 /* read byte(s) */
#define AT25_WRITE 0x02 /* write byte(s)/sector */
#define AT25_SR_nRDY 0x01 /* nRDY = write-in-progress */
#define AT25_SR_WEN 0x02 /* write enable (latched) */
#define AT25_SR_BP0 0x04 /* BP for software writeprotect */
#define AT25_SR_BP1 0x08
#define AT25_SR_WPEN 0x80 /* writeprotect enable */
#define EE_MAXADDRLEN 3 /* 24 bit addresses, up to 2 MBytes */
/* Specs often allow 5 msec for a page write, sometimes 20 msec;
* it's important to recover from write timeouts.
*/
#define EE_TIMEOUT 25
/*-------------------------------------------------------------------------*/
#define io_limit PAGE_SIZE /* bytes */
static ssize_t
at25_ee_read(
struct at25_data *at25,
char *buf,
unsigned offset,
size_t count
)
{
u8 command[EE_MAXADDRLEN + 1];
u8 *cp;
ssize_t status;
struct spi_transfer t[2];
struct spi_message m;
cp = command;
*cp++ = AT25_READ;
/* 8/16/24-bit address is written MSB first */
switch (at25->addrlen) {
default: /* case 3 */
*cp++ = offset >> 16;
case 2:
*cp++ = offset >> 8;
case 1:
case 0: /* can't happen: for better codegen */
*cp++ = offset >> 0;
}
spi_message_init(&m);
memset(t, 0, sizeof t);
t[0].tx_buf = command;
t[0].len = at25->addrlen + 1;
spi_message_add_tail(&t[0], &m);
t[1].rx_buf = buf;
t[1].len = count;
spi_message_add_tail(&t[1], &m);
mutex_lock(&at25->lock);
/* Read it all at once.
*
* REVISIT that's potentially a problem with large chips, if
* other devices on the bus need to be accessed regularly or
* this chip is clocked very slowly
*/
status = spi_sync(at25->spi, &m);
dev_dbg(&at25->spi->dev,
"read %Zd bytes at %d --> %d\n",
count, offset, (int) status);
mutex_unlock(&at25->lock);
return status ? status : count;
}
static ssize_t
at25_bin_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
struct device *dev;
struct at25_data *at25;
dev = container_of(kobj, struct device, kobj);
at25 = dev_get_drvdata(dev);
if (unlikely(off >= at25->bin.size))
return 0;
if ((off + count) > at25->bin.size)
count = at25->bin.size - off;
if (unlikely(!count))
return count;
return at25_ee_read(at25, buf, off, count);
}
static ssize_t
at25_ee_write(struct at25_data *at25, char *buf, loff_t off, size_t count)
{
ssize_t status = 0;
unsigned written = 0;
unsigned buf_size;
u8 *bounce;
/* Temp buffer starts with command and address */
buf_size = at25->chip.page_size;
if (buf_size > io_limit)
buf_size = io_limit;
bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
if (!bounce)
return -ENOMEM;
/* For write, rollover is within the page ... so we write at
* most one page, then manually roll over to the next page.
*/
bounce[0] = AT25_WRITE;
mutex_lock(&at25->lock);
do {
unsigned long timeout, retries;
unsigned segment;
unsigned offset = (unsigned) off;
u8 *cp = bounce + 1;
*cp = AT25_WREN;
status = spi_write(at25->spi, cp, 1);
if (status < 0) {
dev_dbg(&at25->spi->dev, "WREN --> %d\n",
(int) status);
break;
}
/* 8/16/24-bit address is written MSB first */
switch (at25->addrlen) {
default: /* case 3 */
*cp++ = offset >> 16;
case 2:
*cp++ = offset >> 8;
case 1:
case 0: /* can't happen: for better codegen */
*cp++ = offset >> 0;
}
/* Write as much of a page as we can */
segment = buf_size - (offset % buf_size);
if (segment > count)
segment = count;
memcpy(cp, buf, segment);
status = spi_write(at25->spi, bounce,
segment + at25->addrlen + 1);
dev_dbg(&at25->spi->dev,
"write %u bytes at %u --> %d\n",
segment, offset, (int) status);
if (status < 0)
break;
/* REVISIT this should detect (or prevent) failed writes
* to readonly sections of the EEPROM...
*/
/* Wait for non-busy status */
timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
retries = 0;
do {
int sr;
sr = spi_w8r8(at25->spi, AT25_RDSR);
if (sr < 0 || (sr & AT25_SR_nRDY)) {
dev_dbg(&at25->spi->dev,
"rdsr --> %d (%02x)\n", sr, sr);
/* at HZ=100, this is sloooow */
msleep(1);
continue;
}
if (!(sr & AT25_SR_nRDY))
break;
} while (retries++ < 3 || time_before_eq(jiffies, timeout));
if (time_after(jiffies, timeout)) {
dev_err(&at25->spi->dev,
"write %d bytes offset %d, "
"timeout after %u msecs\n",
segment, offset,
jiffies_to_msecs(jiffies -
(timeout - EE_TIMEOUT)));
status = -ETIMEDOUT;
break;
}
off += segment;
buf += segment;
count -= segment;
written += segment;
} while (count > 0);
mutex_unlock(&at25->lock);
kfree(bounce);
return written ? written : status;
}
static ssize_t
at25_bin_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
struct device *dev;
struct at25_data *at25;
dev = container_of(kobj, struct device, kobj);
at25 = dev_get_drvdata(dev);
if (unlikely(off >= at25->bin.size))
return -EFBIG;
if ((off + count) > at25->bin.size)
count = at25->bin.size - off;
if (unlikely(!count))
return count;
return at25_ee_write(at25, buf, off, count);
}
/*-------------------------------------------------------------------------*/
static int at25_probe(struct spi_device *spi)
{
struct at25_data *at25 = NULL;
const struct spi_eeprom *chip;
int err;
int sr;
int addrlen;
/* Chip description */
chip = spi->dev.platform_data;
if (!chip) {
dev_dbg(&spi->dev, "no chip description\n");
err = -ENODEV;
goto fail;
}
/* For now we only support 8/16/24 bit addressing */
if (chip->flags & EE_ADDR1)
addrlen = 1;
else if (chip->flags & EE_ADDR2)
addrlen = 2;
else if (chip->flags & EE_ADDR3)
addrlen = 3;
else {
dev_dbg(&spi->dev, "unsupported address type\n");
err = -EINVAL;
goto fail;
}
/* Ping the chip ... the status register is pretty portable,
* unlike probing manufacturer IDs. We do expect that system
* firmware didn't write it in the past few milliseconds!
*/
sr = spi_w8r8(spi, AT25_RDSR);
if (sr < 0 || sr & AT25_SR_nRDY) {
dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
err = -ENXIO;
goto fail;
}
if (!(at25 = kzalloc(sizeof *at25, GFP_KERNEL))) {
err = -ENOMEM;
goto fail;
}
mutex_init(&at25->lock);
at25->chip = *chip;
at25->spi = spi_dev_get(spi);
dev_set_drvdata(&spi->dev, at25);
at25->addrlen = addrlen;
/* Export the EEPROM bytes through sysfs, since that's convenient.
* Default to root-only access to the data; EEPROMs often hold data
* that's sensitive for read and/or write, like ethernet addresses,
* security codes, board-specific manufacturing calibrations, etc.
*/
at25->bin.attr.name = "eeprom";
at25->bin.attr.mode = S_IRUSR;
at25->bin.read = at25_bin_read;
at25->bin.size = at25->chip.byte_len;
if (!(chip->flags & EE_READONLY)) {
at25->bin.write = at25_bin_write;
at25->bin.attr.mode |= S_IWUSR;
}
err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
if (err)
goto fail;
dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n",
(at25->bin.size < 1024)
? at25->bin.size
: (at25->bin.size / 1024),
(at25->bin.size < 1024) ? "Byte" : "KByte",
at25->chip.name,
(chip->flags & EE_READONLY) ? " (readonly)" : "",
at25->chip.page_size);
return 0;
fail:
dev_dbg(&spi->dev, "probe err %d\n", err);
kfree(at25);
return err;
}
static int __devexit at25_remove(struct spi_device *spi)
{
struct at25_data *at25;
at25 = dev_get_drvdata(&spi->dev);
sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
kfree(at25);
return 0;
}
/*-------------------------------------------------------------------------*/
static struct spi_driver at25_driver = {
.driver = {
.name = "at25",
.owner = THIS_MODULE,
},
.probe = at25_probe,
.remove = __devexit_p(at25_remove),
};
static int __init at25_init(void)
{
return spi_register_driver(&at25_driver);
}
module_init(at25_init);
static void __exit at25_exit(void)
{
spi_unregister_driver(&at25_driver);
}
module_exit(at25_exit);
MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
MODULE_AUTHOR("David Brownell");
MODULE_LICENSE("GPL");
