/* * 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> /* * NOTE: this is an *EEPROM* driver. The vagaries of product naming * mean that some AT25 products are EEPROMs, and others are FLASH. * Handle FLASH chips with the drivers/mtd/devices/m25p80.c driver, * not this one! */ 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, struct bin_attribute *bin_attr, 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, struct bin_attribute *bin_attr, 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");