[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>

3 files changed, 392 insertions, 0 deletions

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index b217a65453f5..9052f4c3493b 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -135,6 +135,16 @@ config SPI_S3C24XX_GPIO
 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 e01104d1ebf8..bf271fe4e536 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_SPI_S3C24XX)		+= spi_s3c24xx.o
 #       ... 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 000000000000..48e4f48e779f
--- /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");
+