mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-05 02:51:00 +00:00
f9c87adc47
Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
244 lines
5.4 KiB
C
244 lines
5.4 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Driver for DS-2502 One wire "Add only Memory".
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*
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* The chip has 4 pages of 32 bytes.
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* In addition it has 8 out of band status bytes that are used, by software,
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* as page redirection bytes by an algorithm described in the data sheet.
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* This is useful since data cannot be erased once written but it can be
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* "patched" up to four times by switching pages.
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*
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* So, when a read request is entirely in the first page automatically
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* apply the page redirection bytes (which allows the device to be seen as
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* a 32 byte PROM, writable 4 times).
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*
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* If the read request is outside of or larger than the first page then read
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* the raw data (which allows the device to be seen as a 128 byte PROM,
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* writable once).
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*
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* Copyright (c) 2018 Flowbird
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* Martin Fuzzey <martin.fuzzey@flowbird.group>
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*/
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#include <common.h>
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#include <dm.h>
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#include <linux/err.h>
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#include <w1-eeprom.h>
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#include <w1.h>
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#define DS2502_PAGE_SIZE 32
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#define DS2502_PAGE_COUNT 4
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#define DS2502_STATUS_SIZE 8
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#define DS2502_CMD_READ_STATUS 0xAA
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#define DS2502_CMD_READ_GEN_CRC 0xC3
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/* u-boot crc8() is CCITT CRC8, we need x^8 + x^5 + x^4 + 1 LSB first */
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static unsigned int ds2502_crc8(const u8 *buf, int len)
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{
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static const u8 poly = 0x8C; /* (1 + x^4 + x^5) + x^8 */
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u8 crc = 0;
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int i;
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for (i = 0; i < len; i++) {
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u8 data = buf[i];
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int j;
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for (j = 0; j < 8; j++) {
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u8 mix = (crc ^ data) & 1;
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crc >>= 1;
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if (mix)
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crc ^= poly;
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data >>= 1;
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}
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}
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return crc;
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}
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static int ds2502_read(struct udevice *dev, u8 cmd,
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int bytes_in_page, int pos,
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u8 *buf, int bytes_for_user)
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{
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int retry;
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int ret = 0;
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for (retry = 0; retry < 3; retry++) {
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u8 pagebuf[DS2502_PAGE_SIZE + 1]; /* 1 byte for CRC8 */
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u8 crc;
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int i;
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ret = w1_reset_select(dev);
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if (ret)
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return ret;
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/* send read to end of page and generate CRC command */
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pagebuf[0] = cmd;
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pagebuf[1] = pos & 0xff;
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pagebuf[2] = pos >> 8;
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crc = ds2502_crc8(pagebuf, 3);
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for (i = 0; i < 3; i++)
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w1_write_byte(dev, pagebuf[i]);
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/* Check command CRC */
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ret = w1_read_byte(dev);
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if (ret < 0) {
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dev_dbg(dev, "Error %d reading command CRC\n", ret);
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continue;
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}
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if (ret != crc) {
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dev_dbg(dev,
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"bad CRC8 for cmd %02x got=%02X exp=%02X\n",
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cmd, ret, crc);
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ret = -EIO;
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continue;
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}
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/* read data and check CRC */
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ret = w1_read_buf(dev, pagebuf, bytes_in_page + 1);
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if (ret < 0) {
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dev_dbg(dev, "Error %d reading data\n", ret);
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continue;
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}
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crc = ds2502_crc8(pagebuf, bytes_in_page);
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if (crc == pagebuf[bytes_in_page]) {
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memcpy(buf, pagebuf, bytes_for_user);
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ret = 0;
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break;
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}
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dev_dbg(dev, "Bad CRC8 got=%02X exp=%02X pos=%04X\n",
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pagebuf[bytes_in_page], crc, pos);
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ret = -EIO;
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}
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return ret;
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}
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static inline int ds2502_read_status_bytes(struct udevice *dev, u8 *buf)
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{
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return ds2502_read(dev, DS2502_CMD_READ_STATUS,
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DS2502_STATUS_SIZE, 0,
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buf, DS2502_STATUS_SIZE);
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}
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/*
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* Status bytes (from index 1) contain 1's complement page indirection
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* So for N writes:
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* N=1: ff ff ff ff ff ff ff 00
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* N=2: ff fe ff ff ff ff ff 00
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* N=3: ff fe fd ff ff ff ff 00
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* N=4: ff fe fd fc ff ff ff 00
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*/
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static int ds2502_indirect_page(struct udevice *dev, u8 *status, int page)
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{
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int page_seen = 0;
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do {
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u8 sb = status[page + 1];
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if (sb == 0xff)
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break;
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page = ~sb & 0xff;
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if (page >= DS2502_PAGE_COUNT) {
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dev_err(dev,
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"Illegal page redirection status byte %02x\n",
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sb);
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return -EINVAL;
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}
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if (page_seen & (1 << page)) {
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dev_err(dev, "Infinite loop in page redirection\n");
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return -EINVAL;
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}
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page_seen |= (1 << page);
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} while (1);
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return page;
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}
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static int ds2502_read_buf(struct udevice *dev, unsigned int offset,
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u8 *buf, unsigned int count)
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{
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unsigned int min_page = offset / DS2502_PAGE_SIZE;
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unsigned int max_page = (offset + count - 1) / DS2502_PAGE_SIZE;
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int xfered = 0;
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u8 status_bytes[DS2502_STATUS_SIZE];
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int i;
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int ret;
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if (min_page >= DS2502_PAGE_COUNT || max_page >= DS2502_PAGE_COUNT)
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return -EINVAL;
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if (min_page == 0 && max_page == 0) {
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ret = ds2502_read_status_bytes(dev, status_bytes);
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if (ret)
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return ret;
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} else {
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/* Dummy one to one page redirection */
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memset(status_bytes, 0xff, sizeof(status_bytes));
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}
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for (i = min_page; i <= max_page; i++) {
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int page;
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int pos;
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int bytes_in_page;
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int bytes_for_user;
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page = ds2502_indirect_page(dev, status_bytes, i);
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if (page < 0)
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return page;
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dev_dbg(dev, "page logical %d => physical %d\n", i, page);
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pos = page * DS2502_PAGE_SIZE;
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if (i == min_page)
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pos += offset % DS2502_PAGE_SIZE;
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bytes_in_page = DS2502_PAGE_SIZE - (pos % DS2502_PAGE_SIZE);
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if (i == max_page)
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bytes_for_user = count - xfered;
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else
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bytes_for_user = bytes_in_page;
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ret = ds2502_read(dev, DS2502_CMD_READ_GEN_CRC,
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bytes_in_page, pos,
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&buf[xfered], bytes_for_user);
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if (ret < 0)
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return ret;
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xfered += bytes_for_user;
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}
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return 0;
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}
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static int ds2502_probe(struct udevice *dev)
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{
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struct w1_device *w1;
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w1 = dev_get_parent_platdata(dev);
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w1->id = 0;
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return 0;
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}
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static const struct w1_eeprom_ops ds2502_ops = {
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.read_buf = ds2502_read_buf,
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};
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static const struct udevice_id ds2502_id[] = {
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{ .compatible = "maxim,ds2502", .data = W1_FAMILY_DS2502 },
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{ },
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};
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U_BOOT_DRIVER(ds2502) = {
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.name = "ds2502",
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.id = UCLASS_W1_EEPROM,
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.of_match = ds2502_id,
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.ops = &ds2502_ops,
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.probe = ds2502_probe,
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};
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