696 lines
17 KiB
C
696 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* i2c-algo-bit.c: i2c driver algorithms for bit-shift adapters
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*
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* Copyright (C) 1995-2000 Simon G. Vogl
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*
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* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
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* <kmalkki@cc.hut.fi> and Jean Delvare <jdelvare@suse.de>
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/delay.h>
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/i2c.h>
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#include <linux/i2c-algo-bit.h>
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/* ----- global defines ----------------------------------------------- */
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#ifdef DEBUG
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#define bit_dbg(level, dev, format, args...) \
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do { \
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if (i2c_debug >= level) \
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dev_dbg(dev, format, ##args); \
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} while (0)
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#else
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#define bit_dbg(level, dev, format, args...) \
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do {} while (0)
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#endif /* DEBUG */
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/* ----- global variables --------------------------------------------- */
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static int bit_test; /* see if the line-setting functions work */
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module_param(bit_test, int, S_IRUGO);
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MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
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#ifdef DEBUG
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static int i2c_debug = 1;
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module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
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MODULE_PARM_DESC(i2c_debug,
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"debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
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#endif
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/* --- setting states on the bus with the right timing: --------------- */
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#define setsda(adap, val) adap->setsda(adap->data, val)
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#define setscl(adap, val) adap->setscl(adap->data, val)
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#define getsda(adap) adap->getsda(adap->data)
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#define getscl(adap) adap->getscl(adap->data)
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static inline void sdalo(struct i2c_algo_bit_data *adap)
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{
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setsda(adap, 0);
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udelay((adap->udelay + 1) / 2);
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}
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static inline void sdahi(struct i2c_algo_bit_data *adap)
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{
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setsda(adap, 1);
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udelay((adap->udelay + 1) / 2);
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}
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static inline void scllo(struct i2c_algo_bit_data *adap)
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{
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setscl(adap, 0);
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udelay(adap->udelay / 2);
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}
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/*
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* Raise scl line, and do checking for delays. This is necessary for slower
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* devices.
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*/
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static int sclhi(struct i2c_algo_bit_data *adap)
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{
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unsigned long start;
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setscl(adap, 1);
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/* Not all adapters have scl sense line... */
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if (!adap->getscl)
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goto done;
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start = jiffies;
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while (!getscl(adap)) {
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/* This hw knows how to read the clock line, so we wait
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* until it actually gets high. This is safer as some
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* chips may hold it low ("clock stretching") while they
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* are processing data internally.
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*/
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if (time_after(jiffies, start + adap->timeout)) {
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/* Test one last time, as we may have been preempted
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* between last check and timeout test.
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*/
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if (getscl(adap))
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break;
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return -ETIMEDOUT;
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}
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cpu_relax();
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}
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#ifdef DEBUG
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if (jiffies != start && i2c_debug >= 3)
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pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go high\n",
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jiffies - start);
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#endif
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done:
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udelay(adap->udelay);
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return 0;
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}
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/* --- other auxiliary functions -------------------------------------- */
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static void i2c_start(struct i2c_algo_bit_data *adap)
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{
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/* assert: scl, sda are high */
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setsda(adap, 0);
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udelay(adap->udelay);
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scllo(adap);
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}
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static void i2c_repstart(struct i2c_algo_bit_data *adap)
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{
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/* assert: scl is low */
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sdahi(adap);
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sclhi(adap);
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setsda(adap, 0);
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udelay(adap->udelay);
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scllo(adap);
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}
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static void i2c_stop(struct i2c_algo_bit_data *adap)
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{
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/* assert: scl is low */
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sdalo(adap);
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sclhi(adap);
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setsda(adap, 1);
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udelay(adap->udelay);
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}
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/* send a byte without start cond., look for arbitration,
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check ackn. from slave */
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/* returns:
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* 1 if the device acknowledged
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* 0 if the device did not ack
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* -ETIMEDOUT if an error occurred (while raising the scl line)
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*/
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static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
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{
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int i;
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int sb;
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int ack;
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struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
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/* assert: scl is low */
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for (i = 7; i >= 0; i--) {
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sb = (c >> i) & 1;
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setsda(adap, sb);
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udelay((adap->udelay + 1) / 2);
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if (sclhi(adap) < 0) { /* timed out */
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bit_dbg(1, &i2c_adap->dev,
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"i2c_outb: 0x%02x, timeout at bit #%d\n",
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(int)c, i);
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return -ETIMEDOUT;
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}
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/* FIXME do arbitration here:
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* if (sb && !getsda(adap)) -> ouch! Get out of here.
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*
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* Report a unique code, so higher level code can retry
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* the whole (combined) message and *NOT* issue STOP.
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*/
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scllo(adap);
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}
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sdahi(adap);
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if (sclhi(adap) < 0) { /* timeout */
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bit_dbg(1, &i2c_adap->dev,
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"i2c_outb: 0x%02x, timeout at ack\n", (int)c);
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return -ETIMEDOUT;
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}
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/* read ack: SDA should be pulled down by slave, or it may
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* NAK (usually to report problems with the data we wrote).
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*/
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ack = !getsda(adap); /* ack: sda is pulled low -> success */
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bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
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ack ? "A" : "NA");
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scllo(adap);
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return ack;
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/* assert: scl is low (sda undef) */
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}
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static int i2c_inb(struct i2c_adapter *i2c_adap)
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{
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/* read byte via i2c port, without start/stop sequence */
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/* acknowledge is sent in i2c_read. */
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int i;
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unsigned char indata = 0;
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struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
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/* assert: scl is low */
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sdahi(adap);
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for (i = 0; i < 8; i++) {
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if (sclhi(adap) < 0) { /* timeout */
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bit_dbg(1, &i2c_adap->dev,
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"i2c_inb: timeout at bit #%d\n",
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7 - i);
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return -ETIMEDOUT;
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}
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indata *= 2;
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if (getsda(adap))
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indata |= 0x01;
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setscl(adap, 0);
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udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
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}
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/* assert: scl is low */
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return indata;
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}
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/*
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* Sanity check for the adapter hardware - check the reaction of
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* the bus lines only if it seems to be idle.
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*/
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static int test_bus(struct i2c_adapter *i2c_adap)
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{
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struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
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const char *name = i2c_adap->name;
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int scl, sda, ret;
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if (adap->pre_xfer) {
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ret = adap->pre_xfer(i2c_adap);
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if (ret < 0)
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return -ENODEV;
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}
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if (adap->getscl == NULL)
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pr_info("%s: Testing SDA only, SCL is not readable\n", name);
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sda = getsda(adap);
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scl = (adap->getscl == NULL) ? 1 : getscl(adap);
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if (!scl || !sda) {
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printk(KERN_WARNING
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"%s: bus seems to be busy (scl=%d, sda=%d)\n",
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name, scl, sda);
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goto bailout;
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}
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sdalo(adap);
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sda = getsda(adap);
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scl = (adap->getscl == NULL) ? 1 : getscl(adap);
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if (sda) {
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printk(KERN_WARNING "%s: SDA stuck high!\n", name);
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goto bailout;
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}
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if (!scl) {
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printk(KERN_WARNING
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"%s: SCL unexpected low while pulling SDA low!\n",
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name);
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goto bailout;
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}
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sdahi(adap);
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sda = getsda(adap);
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scl = (adap->getscl == NULL) ? 1 : getscl(adap);
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if (!sda) {
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printk(KERN_WARNING "%s: SDA stuck low!\n", name);
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goto bailout;
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}
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if (!scl) {
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printk(KERN_WARNING
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"%s: SCL unexpected low while pulling SDA high!\n",
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name);
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goto bailout;
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}
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scllo(adap);
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sda = getsda(adap);
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scl = (adap->getscl == NULL) ? 0 : getscl(adap);
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if (scl) {
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printk(KERN_WARNING "%s: SCL stuck high!\n", name);
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goto bailout;
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}
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if (!sda) {
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printk(KERN_WARNING
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"%s: SDA unexpected low while pulling SCL low!\n",
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name);
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goto bailout;
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}
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sclhi(adap);
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sda = getsda(adap);
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scl = (adap->getscl == NULL) ? 1 : getscl(adap);
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if (!scl) {
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printk(KERN_WARNING "%s: SCL stuck low!\n", name);
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goto bailout;
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}
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if (!sda) {
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printk(KERN_WARNING
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"%s: SDA unexpected low while pulling SCL high!\n",
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name);
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goto bailout;
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}
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if (adap->post_xfer)
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adap->post_xfer(i2c_adap);
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pr_info("%s: Test OK\n", name);
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return 0;
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bailout:
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sdahi(adap);
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sclhi(adap);
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if (adap->post_xfer)
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adap->post_xfer(i2c_adap);
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return -ENODEV;
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}
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/* ----- Utility functions
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*/
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/* try_address tries to contact a chip for a number of
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* times before it gives up.
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* return values:
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* 1 chip answered
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* 0 chip did not answer
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* -x transmission error
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*/
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static int try_address(struct i2c_adapter *i2c_adap,
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unsigned char addr, int retries)
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{
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struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
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int i, ret = 0;
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for (i = 0; i <= retries; i++) {
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ret = i2c_outb(i2c_adap, addr);
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if (ret == 1 || i == retries)
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break;
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bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
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i2c_stop(adap);
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udelay(adap->udelay);
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yield();
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bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
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i2c_start(adap);
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}
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if (i && ret)
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bit_dbg(1, &i2c_adap->dev,
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"Used %d tries to %s client at 0x%02x: %s\n", i + 1,
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addr & 1 ? "read from" : "write to", addr >> 1,
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ret == 1 ? "success" : "failed, timeout?");
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return ret;
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}
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static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
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{
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const unsigned char *temp = msg->buf;
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int count = msg->len;
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unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
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int retval;
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int wrcount = 0;
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while (count > 0) {
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retval = i2c_outb(i2c_adap, *temp);
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/* OK/ACK; or ignored NAK */
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if ((retval > 0) || (nak_ok && (retval == 0))) {
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count--;
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temp++;
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wrcount++;
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/* A slave NAKing the master means the slave didn't like
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* something about the data it saw. For example, maybe
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* the SMBus PEC was wrong.
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*/
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} else if (retval == 0) {
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dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
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return -EIO;
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/* Timeout; or (someday) lost arbitration
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*
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* FIXME Lost ARB implies retrying the transaction from
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* the first message, after the "winning" master issues
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* its STOP. As a rule, upper layer code has no reason
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* to know or care about this ... it is *NOT* an error.
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*/
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} else {
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dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
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retval);
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return retval;
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}
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}
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return wrcount;
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}
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static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
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{
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struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
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/* assert: sda is high */
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if (is_ack) /* send ack */
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setsda(adap, 0);
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udelay((adap->udelay + 1) / 2);
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if (sclhi(adap) < 0) { /* timeout */
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dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
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return -ETIMEDOUT;
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}
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scllo(adap);
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return 0;
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}
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static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
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{
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int inval;
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int rdcount = 0; /* counts bytes read */
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unsigned char *temp = msg->buf;
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int count = msg->len;
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const unsigned flags = msg->flags;
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while (count > 0) {
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inval = i2c_inb(i2c_adap);
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if (inval >= 0) {
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*temp = inval;
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rdcount++;
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} else { /* read timed out */
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break;
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}
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temp++;
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count--;
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/* Some SMBus transactions require that we receive the
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transaction length as the first read byte. */
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if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
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if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
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if (!(flags & I2C_M_NO_RD_ACK))
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acknak(i2c_adap, 0);
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dev_err(&i2c_adap->dev,
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"readbytes: invalid block length (%d)\n",
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inval);
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return -EPROTO;
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}
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/* The original count value accounts for the extra
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bytes, that is, either 1 for a regular transaction,
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or 2 for a PEC transaction. */
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count += inval;
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msg->len += inval;
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}
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bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
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inval,
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(flags & I2C_M_NO_RD_ACK)
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? "(no ack/nak)"
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: (count ? "A" : "NA"));
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if (!(flags & I2C_M_NO_RD_ACK)) {
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inval = acknak(i2c_adap, count);
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if (inval < 0)
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return inval;
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}
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}
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return rdcount;
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}
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/* doAddress initiates the transfer by generating the start condition (in
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* try_address) and transmits the address in the necessary format to handle
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* reads, writes as well as 10bit-addresses.
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* returns:
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* 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
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* -x an error occurred (like: -ENXIO if the device did not answer, or
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* -ETIMEDOUT, for example if the lines are stuck...)
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*/
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static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
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{
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unsigned short flags = msg->flags;
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unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
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struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
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unsigned char addr;
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int ret, retries;
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retries = nak_ok ? 0 : i2c_adap->retries;
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if (flags & I2C_M_TEN) {
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/* a ten bit address */
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addr = 0xf0 | ((msg->addr >> 7) & 0x06);
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bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
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/* try extended address code...*/
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ret = try_address(i2c_adap, addr, retries);
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if ((ret != 1) && !nak_ok) {
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dev_err(&i2c_adap->dev,
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"died at extended address code\n");
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return -ENXIO;
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}
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/* the remaining 8 bit address */
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ret = i2c_outb(i2c_adap, msg->addr & 0xff);
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if ((ret != 1) && !nak_ok) {
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/* the chip did not ack / xmission error occurred */
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dev_err(&i2c_adap->dev, "died at 2nd address code\n");
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return -ENXIO;
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}
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if (flags & I2C_M_RD) {
|
|
bit_dbg(3, &i2c_adap->dev,
|
|
"emitting repeated start condition\n");
|
|
i2c_repstart(adap);
|
|
/* okay, now switch into reading mode */
|
|
addr |= 0x01;
|
|
ret = try_address(i2c_adap, addr, retries);
|
|
if ((ret != 1) && !nak_ok) {
|
|
dev_err(&i2c_adap->dev,
|
|
"died at repeated address code\n");
|
|
return -EIO;
|
|
}
|
|
}
|
|
} else { /* normal 7bit address */
|
|
addr = i2c_8bit_addr_from_msg(msg);
|
|
if (flags & I2C_M_REV_DIR_ADDR)
|
|
addr ^= 1;
|
|
ret = try_address(i2c_adap, addr, retries);
|
|
if ((ret != 1) && !nak_ok)
|
|
return -ENXIO;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int bit_xfer(struct i2c_adapter *i2c_adap,
|
|
struct i2c_msg msgs[], int num)
|
|
{
|
|
struct i2c_msg *pmsg;
|
|
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
|
|
int i, ret;
|
|
unsigned short nak_ok;
|
|
|
|
if (adap->pre_xfer) {
|
|
ret = adap->pre_xfer(i2c_adap);
|
|
if (ret < 0)
|
|
return ret;
|
|
}
|
|
|
|
bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
|
|
i2c_start(adap);
|
|
for (i = 0; i < num; i++) {
|
|
pmsg = &msgs[i];
|
|
nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
|
|
if (!(pmsg->flags & I2C_M_NOSTART)) {
|
|
if (i) {
|
|
if (msgs[i - 1].flags & I2C_M_STOP) {
|
|
bit_dbg(3, &i2c_adap->dev,
|
|
"emitting enforced stop/start condition\n");
|
|
i2c_stop(adap);
|
|
i2c_start(adap);
|
|
} else {
|
|
bit_dbg(3, &i2c_adap->dev,
|
|
"emitting repeated start condition\n");
|
|
i2c_repstart(adap);
|
|
}
|
|
}
|
|
ret = bit_doAddress(i2c_adap, pmsg);
|
|
if ((ret != 0) && !nak_ok) {
|
|
bit_dbg(1, &i2c_adap->dev,
|
|
"NAK from device addr 0x%02x msg #%d\n",
|
|
msgs[i].addr, i);
|
|
goto bailout;
|
|
}
|
|
}
|
|
if (pmsg->flags & I2C_M_RD) {
|
|
/* read bytes into buffer*/
|
|
ret = readbytes(i2c_adap, pmsg);
|
|
if (ret >= 1)
|
|
bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
|
|
ret, ret == 1 ? "" : "s");
|
|
if (ret < pmsg->len) {
|
|
if (ret >= 0)
|
|
ret = -EIO;
|
|
goto bailout;
|
|
}
|
|
} else {
|
|
/* write bytes from buffer */
|
|
ret = sendbytes(i2c_adap, pmsg);
|
|
if (ret >= 1)
|
|
bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
|
|
ret, ret == 1 ? "" : "s");
|
|
if (ret < pmsg->len) {
|
|
if (ret >= 0)
|
|
ret = -EIO;
|
|
goto bailout;
|
|
}
|
|
}
|
|
}
|
|
ret = i;
|
|
|
|
bailout:
|
|
bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
|
|
i2c_stop(adap);
|
|
|
|
if (adap->post_xfer)
|
|
adap->post_xfer(i2c_adap);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* We print a warning when we are not flagged to support atomic transfers but
|
|
* will try anyhow. That's what the I2C core would do as well. Sadly, we can't
|
|
* modify the algorithm struct at probe time because this struct is exported
|
|
* 'const'.
|
|
*/
|
|
static int bit_xfer_atomic(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[],
|
|
int num)
|
|
{
|
|
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
|
|
|
|
if (!adap->can_do_atomic)
|
|
dev_warn(&i2c_adap->dev, "not flagged for atomic transfers\n");
|
|
|
|
return bit_xfer(i2c_adap, msgs, num);
|
|
}
|
|
|
|
static u32 bit_func(struct i2c_adapter *adap)
|
|
{
|
|
return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL_ALL |
|
|
I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
|
|
}
|
|
|
|
|
|
/* -----exported algorithm data: ------------------------------------- */
|
|
|
|
const struct i2c_algorithm i2c_bit_algo = {
|
|
.master_xfer = bit_xfer,
|
|
.master_xfer_atomic = bit_xfer_atomic,
|
|
.functionality = bit_func,
|
|
};
|
|
EXPORT_SYMBOL(i2c_bit_algo);
|
|
|
|
static const struct i2c_adapter_quirks i2c_bit_quirk_no_clk_stretch = {
|
|
.flags = I2C_AQ_NO_CLK_STRETCH,
|
|
};
|
|
|
|
/*
|
|
* registering functions to load algorithms at runtime
|
|
*/
|
|
static int __i2c_bit_add_bus(struct i2c_adapter *adap,
|
|
int (*add_adapter)(struct i2c_adapter *))
|
|
{
|
|
struct i2c_algo_bit_data *bit_adap = adap->algo_data;
|
|
int ret;
|
|
|
|
if (bit_test) {
|
|
ret = test_bus(adap);
|
|
if (bit_test >= 2 && ret < 0)
|
|
return -ENODEV;
|
|
}
|
|
|
|
/* register new adapter to i2c module... */
|
|
adap->algo = &i2c_bit_algo;
|
|
adap->retries = 3;
|
|
if (bit_adap->getscl == NULL)
|
|
adap->quirks = &i2c_bit_quirk_no_clk_stretch;
|
|
|
|
/*
|
|
* We tried forcing SCL/SDA to an initial state here. But that caused a
|
|
* regression, sadly. Check Bugzilla #200045 for details.
|
|
*/
|
|
|
|
ret = add_adapter(adap);
|
|
if (ret < 0)
|
|
return ret;
|
|
|
|
/* Complain if SCL can't be read */
|
|
if (bit_adap->getscl == NULL) {
|
|
dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
|
|
dev_warn(&adap->dev, "Bus may be unreliable\n");
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
int i2c_bit_add_bus(struct i2c_adapter *adap)
|
|
{
|
|
return __i2c_bit_add_bus(adap, i2c_add_adapter);
|
|
}
|
|
EXPORT_SYMBOL(i2c_bit_add_bus);
|
|
|
|
int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
|
|
{
|
|
return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
|
|
}
|
|
EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
|
|
|
|
MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
|
|
MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
|
|
MODULE_LICENSE("GPL");
|