[PATCH] SPI eeprom driver
This is adds a simple SPI EEPROM driver, providing access to the EEPROM
through sysfs much like the I2C "eeprom" driver ... except this driver
supports write access, and multiple EEPROM sizes.
From: "Tuppa, Walter" <walter.tuppa@siemens.com>
Since I have EEPROMs on SPI with different address sizing, I made some
changes to your at25.c to support them. Works perfectly. (Also includes a
small bugfix for the "what size address" test.)
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Walter Tuppa <walter.tuppa@siemens.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index b217a65..9052f4c 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -135,6 +135,16 @@
comment "SPI Protocol Masters"
depends on SPI_MASTER
+config SPI_AT25
+ tristate "SPI EEPROMs from most vendors"
+ depends on SPI_MASTER && SYSFS
+ help
+ Enable this driver to get read/write support to most SPI EEPROMs,
+ after you configure the board init code to know about each eeprom
+ on your target board.
+
+ This driver can also be built as a module. If so, the module
+ will be called at25.
#
# Add new SPI protocol masters in alphabetical order above this line
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index e01104d..bf271fe 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -22,6 +22,7 @@
# ... add above this line ...
# SPI protocol drivers (device/link on bus)
+obj-$(CONFIG_SPI_AT25) += at25.o
# ... add above this line ...
# SPI slave controller drivers (upstream link)
diff --git a/drivers/spi/at25.c b/drivers/spi/at25.c
new file mode 100644
index 0000000..48e4f48
--- /dev/null
+++ b/drivers/spi/at25.c
@@ -0,0 +1,381 @@
+/*
+ * 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(&at25->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.attr.owner = THIS_MODULE;
+ 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");
+
diff --git a/include/linux/spi/eeprom.h b/include/linux/spi/eeprom.h
new file mode 100644
index 0000000..1085212
--- /dev/null
+++ b/include/linux/spi/eeprom.h
@@ -0,0 +1,22 @@
+#ifndef __LINUX_SPI_EEPROM_H
+#define __LINUX_SPI_EEPROM_H
+
+/*
+ * Put one of these structures in platform_data for SPI EEPROMS handled
+ * by the "at25" driver. On SPI, most EEPROMS understand the same core
+ * command set. If you need to support EEPROMs that don't yet fit, add
+ * flags to support those protocol options. These values all come from
+ * the chip datasheets.
+ */
+struct spi_eeprom {
+ u32 byte_len;
+ char name[10];
+ u16 page_size; /* for writes */
+ u16 flags;
+#define EE_ADDR1 0x0001 /* 8 bit addrs */
+#define EE_ADDR2 0x0002 /* 16 bit addrs */
+#define EE_ADDR3 0x0004 /* 24 bit addrs */
+#define EE_READONLY 0x0008 /* disallow writes */
+};
+
+#endif /* __LINUX_SPI_EEPROM_H */
