diff options
Diffstat (limited to 'drivers/misc/eeprom/at24.c')
| -rw-r--r-- | drivers/misc/eeprom/at24.c | 582 |
1 files changed, 582 insertions, 0 deletions
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c new file mode 100644 index 00000000000..d4775528abc --- /dev/null +++ b/drivers/misc/eeprom/at24.c @@ -0,0 +1,582 @@ +/* + * at24.c - handle most I2C EEPROMs + * + * Copyright (C) 2005-2007 David Brownell + * Copyright (C) 2008 Wolfram Sang, Pengutronix + * + * 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/mutex.h> +#include <linux/sysfs.h> +#include <linux/mod_devicetable.h> +#include <linux/log2.h> +#include <linux/bitops.h> +#include <linux/jiffies.h> +#include <linux/i2c.h> +#include <linux/i2c/at24.h> + +/* + * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable. + * Differences between different vendor product lines (like Atmel AT24C or + * MicroChip 24LC, etc) won't much matter for typical read/write access. + * There are also I2C RAM chips, likewise interchangeable. One example + * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes). + * + * However, misconfiguration can lose data. "Set 16-bit memory address" + * to a part with 8-bit addressing will overwrite data. Writing with too + * big a page size also loses data. And it's not safe to assume that the + * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC + * uses 0x51, for just one example. + * + * Accordingly, explicit board-specific configuration data should be used + * in almost all cases. (One partial exception is an SMBus used to access + * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.) + * + * So this driver uses "new style" I2C driver binding, expecting to be + * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or + * similar kernel-resident tables; or, configuration data coming from + * a bootloader. + * + * Other than binding model, current differences from "eeprom" driver are + * that this one handles write access and isn't restricted to 24c02 devices. + * It also handles larger devices (32 kbit and up) with two-byte addresses, + * which won't work on pure SMBus systems. + */ + +struct at24_data { + struct at24_platform_data chip; + bool use_smbus; + + /* + * Lock protects against activities from other Linux tasks, + * but not from changes by other I2C masters. + */ + struct mutex lock; + struct bin_attribute bin; + + u8 *writebuf; + unsigned write_max; + unsigned num_addresses; + + /* + * Some chips tie up multiple I2C addresses; dummy devices reserve + * them for us, and we'll use them with SMBus calls. + */ + struct i2c_client *client[]; +}; + +/* + * This parameter is to help this driver avoid blocking other drivers out + * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C + * clock, one 256 byte read takes about 1/43 second which is excessive; + * but the 1/170 second it takes at 400 kHz may be quite reasonable; and + * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible. + * + * This value is forced to be a power of two so that writes align on pages. + */ +static unsigned io_limit = 128; +module_param(io_limit, uint, 0); +MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)"); + +/* + * Specs often allow 5 msec for a page write, sometimes 20 msec; + * it's important to recover from write timeouts. + */ +static unsigned write_timeout = 25; +module_param(write_timeout, uint, 0); +MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)"); + +#define AT24_SIZE_BYTELEN 5 +#define AT24_SIZE_FLAGS 8 + +#define AT24_BITMASK(x) (BIT(x) - 1) + +/* create non-zero magic value for given eeprom parameters */ +#define AT24_DEVICE_MAGIC(_len, _flags) \ + ((1 << AT24_SIZE_FLAGS | (_flags)) \ + << AT24_SIZE_BYTELEN | ilog2(_len)) + +static const struct i2c_device_id at24_ids[] = { + /* needs 8 addresses as A0-A2 are ignored */ + { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) }, + /* old variants can't be handled with this generic entry! */ + { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) }, + { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) }, + /* spd is a 24c02 in memory DIMMs */ + { "spd", AT24_DEVICE_MAGIC(2048 / 8, + AT24_FLAG_READONLY | AT24_FLAG_IRUGO) }, + { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) }, + /* 24rf08 quirk is handled at i2c-core */ + { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) }, + { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) }, + { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) }, + { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) }, + { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) }, + { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) }, + { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) }, + { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) }, + { "at24", 0 }, + { /* END OF LIST */ } +}; +MODULE_DEVICE_TABLE(i2c, at24_ids); + +/*-------------------------------------------------------------------------*/ + +/* + * This routine supports chips which consume multiple I2C addresses. It + * computes the addressing information to be used for a given r/w request. + * Assumes that sanity checks for offset happened at sysfs-layer. + */ +static struct i2c_client *at24_translate_offset(struct at24_data *at24, + unsigned *offset) +{ + unsigned i; + + if (at24->chip.flags & AT24_FLAG_ADDR16) { + i = *offset >> 16; + *offset &= 0xffff; + } else { + i = *offset >> 8; + *offset &= 0xff; + } + + return at24->client[i]; +} + +static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf, + unsigned offset, size_t count) +{ + struct i2c_msg msg[2]; + u8 msgbuf[2]; + struct i2c_client *client; + int status, i; + + memset(msg, 0, sizeof(msg)); + + /* + * REVISIT some multi-address chips don't rollover page reads to + * the next slave address, so we may need to truncate the count. + * Those chips might need another quirk flag. + * + * If the real hardware used four adjacent 24c02 chips and that + * were misconfigured as one 24c08, that would be a similar effect: + * one "eeprom" file not four, but larger reads would fail when + * they crossed certain pages. + */ + + /* + * Slave address and byte offset derive from the offset. Always + * set the byte address; on a multi-master board, another master + * may have changed the chip's "current" address pointer. + */ + client = at24_translate_offset(at24, &offset); + + if (count > io_limit) + count = io_limit; + + /* Smaller eeproms can work given some SMBus extension calls */ + if (at24->use_smbus) { + if (count > I2C_SMBUS_BLOCK_MAX) + count = I2C_SMBUS_BLOCK_MAX; + status = i2c_smbus_read_i2c_block_data(client, offset, + count, buf); + dev_dbg(&client->dev, "smbus read %zu@%d --> %d\n", + count, offset, status); + return (status < 0) ? -EIO : status; + } + + /* + * When we have a better choice than SMBus calls, use a combined + * I2C message. Write address; then read up to io_limit data bytes. + * Note that read page rollover helps us here (unlike writes). + * msgbuf is u8 and will cast to our needs. + */ + i = 0; + if (at24->chip.flags & AT24_FLAG_ADDR16) + msgbuf[i++] = offset >> 8; + msgbuf[i++] = offset; + + msg[0].addr = client->addr; + msg[0].buf = msgbuf; + msg[0].len = i; + + msg[1].addr = client->addr; + msg[1].flags = I2C_M_RD; + msg[1].buf = buf; + msg[1].len = count; + + status = i2c_transfer(client->adapter, msg, 2); + dev_dbg(&client->dev, "i2c read %zu@%d --> %d\n", + count, offset, status); + + if (status == 2) + return count; + else if (status >= 0) + return -EIO; + else + return status; +} + +static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr, + char *buf, loff_t off, size_t count) +{ + struct at24_data *at24; + ssize_t retval = 0; + + at24 = dev_get_drvdata(container_of(kobj, struct device, kobj)); + + if (unlikely(!count)) + return count; + + /* + * Read data from chip, protecting against concurrent updates + * from this host, but not from other I2C masters. + */ + mutex_lock(&at24->lock); + + while (count) { + ssize_t status; + + status = at24_eeprom_read(at24, buf, off, count); + if (status <= 0) { + if (retval == 0) + retval = status; + break; + } + buf += status; + off += status; + count -= status; + retval += status; + } + + mutex_unlock(&at24->lock); + + return retval; +} + + +/* + * REVISIT: export at24_bin{read,write}() to let other kernel code use + * eeprom data. For example, it might hold a board's Ethernet address, or + * board-specific calibration data generated on the manufacturing floor. + */ + + +/* + * Note that if the hardware write-protect pin is pulled high, the whole + * chip is normally write protected. But there are plenty of product + * variants here, including OTP fuses and partial chip protect. + * + * We only use page mode writes; the alternative is sloooow. This routine + * writes at most one page. + */ +static ssize_t at24_eeprom_write(struct at24_data *at24, char *buf, + unsigned offset, size_t count) +{ + struct i2c_client *client; + struct i2c_msg msg; + ssize_t status; + unsigned long timeout, write_time; + unsigned next_page; + + /* Get corresponding I2C address and adjust offset */ + client = at24_translate_offset(at24, &offset); + + /* write_max is at most a page */ + if (count > at24->write_max) + count = at24->write_max; + + /* Never roll over backwards, to the start of this page */ + next_page = roundup(offset + 1, at24->chip.page_size); + if (offset + count > next_page) + count = next_page - offset; + + /* If we'll use I2C calls for I/O, set up the message */ + if (!at24->use_smbus) { + int i = 0; + + msg.addr = client->addr; + msg.flags = 0; + + /* msg.buf is u8 and casts will mask the values */ + msg.buf = at24->writebuf; + if (at24->chip.flags & AT24_FLAG_ADDR16) + msg.buf[i++] = offset >> 8; + + msg.buf[i++] = offset; + memcpy(&msg.buf[i], buf, count); + msg.len = i + count; + } + + /* + * Writes fail if the previous one didn't complete yet. We may + * loop a few times until this one succeeds, waiting at least + * long enough for one entire page write to work. + */ + timeout = jiffies + msecs_to_jiffies(write_timeout); + do { + write_time = jiffies; + if (at24->use_smbus) { + status = i2c_smbus_write_i2c_block_data(client, + offset, count, buf); + if (status == 0) + status = count; + } else { + status = i2c_transfer(client->adapter, &msg, 1); + if (status == 1) + status = count; + } + dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n", + count, offset, status, jiffies); + + if (status == count) + return count; + + /* REVISIT: at HZ=100, this is sloooow */ + msleep(1); + } while (time_before(write_time, timeout)); + + return -ETIMEDOUT; +} + +static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr, + char *buf, loff_t off, size_t count) +{ + struct at24_data *at24; + ssize_t retval = 0; + + at24 = dev_get_drvdata(container_of(kobj, struct device, kobj)); + + if (unlikely(!count)) + return count; + + /* + * Write data to chip, protecting against concurrent updates + * from this host, but not from other I2C masters. + */ + mutex_lock(&at24->lock); + + while (count) { + ssize_t status; + + status = at24_eeprom_write(at24, buf, off, count); + if (status <= 0) { + if (retval == 0) + retval = status; + break; + } + buf += status; + off += status; + count -= status; + retval += status; + } + + mutex_unlock(&at24->lock); + + return retval; +} + +/*-------------------------------------------------------------------------*/ + +static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) +{ + struct at24_platform_data chip; + bool writable; + bool use_smbus = false; + struct at24_data *at24; + int err; + unsigned i, num_addresses; + kernel_ulong_t magic; + + if (client->dev.platform_data) { + chip = *(struct at24_platform_data *)client->dev.platform_data; + } else { + if (!id->driver_data) { + err = -ENODEV; + goto err_out; + } + magic = id->driver_data; + chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN)); + magic >>= AT24_SIZE_BYTELEN; + chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS); + /* + * This is slow, but we can't know all eeproms, so we better + * play safe. Specifying custom eeprom-types via platform_data + * is recommended anyhow. + */ + chip.page_size = 1; + } + + if (!is_power_of_2(chip.byte_len)) + dev_warn(&client->dev, + "byte_len looks suspicious (no power of 2)!\n"); + if (!is_power_of_2(chip.page_size)) + dev_warn(&client->dev, + "page_size looks suspicious (no power of 2)!\n"); + + /* Use I2C operations unless we're stuck with SMBus extensions. */ + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { + if (chip.flags & AT24_FLAG_ADDR16) { + err = -EPFNOSUPPORT; + goto err_out; + } + if (!i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { + err = -EPFNOSUPPORT; + goto err_out; + } + use_smbus = true; + } + + if (chip.flags & AT24_FLAG_TAKE8ADDR) + num_addresses = 8; + else + num_addresses = DIV_ROUND_UP(chip.byte_len, + (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256); + + at24 = kzalloc(sizeof(struct at24_data) + + num_addresses * sizeof(struct i2c_client *), GFP_KERNEL); + if (!at24) { + err = -ENOMEM; + goto err_out; + } + + mutex_init(&at24->lock); + at24->use_smbus = use_smbus; + at24->chip = chip; + at24->num_addresses = num_addresses; + + /* + * Export the EEPROM bytes through sysfs, since that's convenient. + * By default, only root should see the data (maybe passwords etc) + */ + at24->bin.attr.name = "eeprom"; + at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR; + at24->bin.read = at24_bin_read; + at24->bin.size = chip.byte_len; + + writable = !(chip.flags & AT24_FLAG_READONLY); + if (writable) { + if (!use_smbus || i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) { + + unsigned write_max = chip.page_size; + + at24->bin.write = at24_bin_write; + at24->bin.attr.mode |= S_IWUSR; + + if (write_max > io_limit) + write_max = io_limit; + if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX) + write_max = I2C_SMBUS_BLOCK_MAX; + at24->write_max = write_max; + + /* buffer (data + address at the beginning) */ + at24->writebuf = kmalloc(write_max + 2, GFP_KERNEL); + if (!at24->writebuf) { + err = -ENOMEM; + goto err_struct; + } + } else { + dev_warn(&client->dev, + "cannot write due to controller restrictions."); + } + } + + at24->client[0] = client; + + /* use dummy devices for multiple-address chips */ + for (i = 1; i < num_addresses; i++) { + at24->client[i] = i2c_new_dummy(client->adapter, + client->addr + i); + if (!at24->client[i]) { + dev_err(&client->dev, "address 0x%02x unavailable\n", + client->addr + i); + err = -EADDRINUSE; + goto err_clients; + } + } + + err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin); + if (err) + goto err_clients; + + i2c_set_clientdata(client, at24); + + dev_info(&client->dev, "%zu byte %s EEPROM %s\n", + at24->bin.size, client->name, + writable ? "(writable)" : "(read-only)"); + dev_dbg(&client->dev, + "page_size %d, num_addresses %d, write_max %d%s\n", + chip.page_size, num_addresses, + at24->write_max, + use_smbus ? ", use_smbus" : ""); + + return 0; + +err_clients: + for (i = 1; i < num_addresses; i++) + if (at24->client[i]) + i2c_unregister_device(at24->client[i]); + + kfree(at24->writebuf); +err_struct: + kfree(at24); +err_out: + dev_dbg(&client->dev, "probe error %d\n", err); + return err; +} + +static int __devexit at24_remove(struct i2c_client *client) +{ + struct at24_data *at24; + int i; + + at24 = i2c_get_clientdata(client); + sysfs_remove_bin_file(&client->dev.kobj, &at24->bin); + + for (i = 1; i < at24->num_addresses; i++) + i2c_unregister_device(at24->client[i]); + + kfree(at24->writebuf); + kfree(at24); + i2c_set_clientdata(client, NULL); + return 0; +} + +/*-------------------------------------------------------------------------*/ + +static struct i2c_driver at24_driver = { + .driver = { + .name = "at24", + .owner = THIS_MODULE, + }, + .probe = at24_probe, + .remove = __devexit_p(at24_remove), + .id_table = at24_ids, +}; + +static int __init at24_init(void) +{ + io_limit = rounddown_pow_of_two(io_limit); + return i2c_add_driver(&at24_driver); +} +module_init(at24_init); + +static void __exit at24_exit(void) +{ + i2c_del_driver(&at24_driver); +} +module_exit(at24_exit); + +MODULE_DESCRIPTION("Driver for most I2C EEPROMs"); +MODULE_AUTHOR("David Brownell and Wolfram Sang"); +MODULE_LICENSE("GPL"); |