diff options
Diffstat (limited to 'drivers/misc/eeprom/at25.c')
| -rw-r--r-- | drivers/misc/eeprom/at25.c | 400 |
1 files changed, 400 insertions, 0 deletions
diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c new file mode 100644 index 000000000..3b7d8b758 --- /dev/null +++ b/drivers/misc/eeprom/at25.c @@ -0,0 +1,400 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * at25.c -- support most SPI EEPROMs, such as Atmel AT25 models + * + * Copyright (C) 2006 David Brownell + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/delay.h> +#include <linux/device.h> +#include <linux/sched.h> + +#include <linux/nvmem-provider.h> +#include <linux/spi/spi.h> +#include <linux/spi/eeprom.h> +#include <linux/property.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; + unsigned addrlen; + struct nvmem_config nvmem_config; + struct nvmem_device *nvmem; +}; + +#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 AT25_INSTR_BIT3 0x08 /* Additional address bit in instr */ + +#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 int at25_ee_read(void *priv, unsigned int offset, + void *val, size_t count) +{ + struct at25_data *at25 = priv; + char *buf = val; + u8 command[EE_MAXADDRLEN + 1]; + u8 *cp; + ssize_t status; + struct spi_transfer t[2]; + struct spi_message m; + u8 instr; + + if (unlikely(offset >= at25->chip.byte_len)) + return -EINVAL; + if ((offset + count) > at25->chip.byte_len) + count = at25->chip.byte_len - offset; + if (unlikely(!count)) + return -EINVAL; + + cp = command; + + instr = AT25_READ; + if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) + if (offset >= (1U << (at25->addrlen * 8))) + instr |= AT25_INSTR_BIT3; + *cp++ = instr; + + /* 8/16/24-bit address is written MSB first */ + switch (at25->addrlen) { + default: /* case 3 */ + *cp++ = offset >> 16; + fallthrough; + case 2: + *cp++ = offset >> 8; + fallthrough; + 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 %zu bytes at %d --> %zd\n", + count, offset, status); + + mutex_unlock(&at25->lock); + return status; +} + +static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count) +{ + struct at25_data *at25 = priv; + const char *buf = val; + int status = 0; + unsigned buf_size; + u8 *bounce; + + if (unlikely(off >= at25->chip.byte_len)) + return -EFBIG; + if ((off + count) > at25->chip.byte_len) + count = at25->chip.byte_len - off; + if (unlikely(!count)) + return -EINVAL; + + /* 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. + */ + mutex_lock(&at25->lock); + do { + unsigned long timeout, retries; + unsigned segment; + unsigned offset = (unsigned) off; + u8 *cp = bounce; + int sr; + u8 instr; + + *cp = AT25_WREN; + status = spi_write(at25->spi, cp, 1); + if (status < 0) { + dev_dbg(&at25->spi->dev, "WREN --> %d\n", status); + break; + } + + instr = AT25_WRITE; + if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) + if (offset >= (1U << (at25->addrlen * 8))) + instr |= AT25_INSTR_BIT3; + *cp++ = instr; + + /* 8/16/24-bit address is written MSB first */ + switch (at25->addrlen) { + default: /* case 3 */ + *cp++ = offset >> 16; + fallthrough; + case 2: + *cp++ = offset >> 8; + fallthrough; + 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, 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 { + + 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 ((sr < 0) || (sr & AT25_SR_nRDY)) { + dev_err(&at25->spi->dev, + "write %u bytes offset %u, timeout after %u msecs\n", + segment, offset, + jiffies_to_msecs(jiffies - + (timeout - EE_TIMEOUT))); + status = -ETIMEDOUT; + break; + } + + off += segment; + buf += segment; + count -= segment; + + } while (count > 0); + + mutex_unlock(&at25->lock); + + kfree(bounce); + return status; +} + +/*-------------------------------------------------------------------------*/ + +static int at25_fw_to_chip(struct device *dev, struct spi_eeprom *chip) +{ + u32 val; + + memset(chip, 0, sizeof(*chip)); + strncpy(chip->name, "at25", sizeof(chip->name)); + + if (device_property_read_u32(dev, "size", &val) == 0 || + device_property_read_u32(dev, "at25,byte-len", &val) == 0) { + chip->byte_len = val; + } else { + dev_err(dev, "Error: missing \"size\" property\n"); + return -ENODEV; + } + + if (device_property_read_u32(dev, "pagesize", &val) == 0 || + device_property_read_u32(dev, "at25,page-size", &val) == 0) { + chip->page_size = val; + } else { + dev_err(dev, "Error: missing \"pagesize\" property\n"); + return -ENODEV; + } + + if (device_property_read_u32(dev, "at25,addr-mode", &val) == 0) { + chip->flags = (u16)val; + } else { + if (device_property_read_u32(dev, "address-width", &val)) { + dev_err(dev, + "Error: missing \"address-width\" property\n"); + return -ENODEV; + } + switch (val) { + case 9: + chip->flags |= EE_INSTR_BIT3_IS_ADDR; + fallthrough; + case 8: + chip->flags |= EE_ADDR1; + break; + case 16: + chip->flags |= EE_ADDR2; + break; + case 24: + chip->flags |= EE_ADDR3; + break; + default: + dev_err(dev, + "Error: bad \"address-width\" property: %u\n", + val); + return -ENODEV; + } + if (device_property_present(dev, "read-only")) + chip->flags |= EE_READONLY; + } + return 0; +} + +static int at25_probe(struct spi_device *spi) +{ + struct at25_data *at25 = NULL; + struct spi_eeprom chip; + int err; + int sr; + int addrlen; + + /* Chip description */ + if (!spi->dev.platform_data) { + err = at25_fw_to_chip(&spi->dev, &chip); + if (err) + return err; + } else + chip = *(struct spi_eeprom *)spi->dev.platform_data; + + /* 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"); + return -EINVAL; + } + + /* 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); + return -ENXIO; + } + + at25 = devm_kzalloc(&spi->dev, sizeof(struct at25_data), GFP_KERNEL); + if (!at25) + return -ENOMEM; + + mutex_init(&at25->lock); + at25->chip = chip; + at25->spi = spi; + spi_set_drvdata(spi, at25); + at25->addrlen = addrlen; + + at25->nvmem_config.type = NVMEM_TYPE_EEPROM; + at25->nvmem_config.name = dev_name(&spi->dev); + at25->nvmem_config.dev = &spi->dev; + at25->nvmem_config.read_only = chip.flags & EE_READONLY; + at25->nvmem_config.root_only = true; + at25->nvmem_config.owner = THIS_MODULE; + at25->nvmem_config.compat = true; + at25->nvmem_config.base_dev = &spi->dev; + at25->nvmem_config.reg_read = at25_ee_read; + at25->nvmem_config.reg_write = at25_ee_write; + at25->nvmem_config.priv = at25; + at25->nvmem_config.stride = 1; + at25->nvmem_config.word_size = 1; + at25->nvmem_config.size = chip.byte_len; + + at25->nvmem = devm_nvmem_register(&spi->dev, &at25->nvmem_config); + if (IS_ERR(at25->nvmem)) + return PTR_ERR(at25->nvmem); + + dev_info(&spi->dev, "%d %s %s eeprom%s, pagesize %u\n", + (chip.byte_len < 1024) ? chip.byte_len : (chip.byte_len / 1024), + (chip.byte_len < 1024) ? "Byte" : "KByte", + at25->chip.name, + (chip.flags & EE_READONLY) ? " (readonly)" : "", + at25->chip.page_size); + return 0; +} + +/*-------------------------------------------------------------------------*/ + +static const struct of_device_id at25_of_match[] = { + { .compatible = "atmel,at25", }, + { } +}; +MODULE_DEVICE_TABLE(of, at25_of_match); + +static struct spi_driver at25_driver = { + .driver = { + .name = "at25", + .of_match_table = at25_of_match, + }, + .probe = at25_probe, +}; + +module_spi_driver(at25_driver); + +MODULE_DESCRIPTION("Driver for most SPI EEPROMs"); +MODULE_AUTHOR("David Brownell"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("spi:at25"); |