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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* I2C bus driver for Kontron COM modules
*
* Based on the similar driver in Linux.
*/
#include <stdint.h>
#include <console/console.h>
#include <device/device.h>
#include <device/i2c_bus.h>
#include <timer.h>
#include <delay.h>
#include "kempld.h"
#include "kempld_internal.h"
#define KEMPLD_I2C_PRELOW 0x0b
#define KEMPLD_I2C_PREHIGH 0x0c
#define KEMPLD_I2C_DATA 0x0e
#define KEMPLD_I2C_CTRL 0x0d
#define I2C_CTRL_IEN 0x40
#define I2C_CTRL_EN 0x80
#define KEMPLD_I2C_STAT 0x0f
#define I2C_STAT_IF 0x01
#define I2C_STAT_TIP 0x02
#define I2C_STAT_ARBLOST 0x20
#define I2C_STAT_BUSY 0x40
#define I2C_STAT_NACK 0x80
#define KEMPLD_I2C_CMD 0x0f
#define I2C_CMD_START 0x91
#define I2C_CMD_STOP 0x41
#define I2C_CMD_READ 0x21
#define I2C_CMD_WRITE 0x11
#define I2C_CMD_READ_ACK 0x21
#define I2C_CMD_READ_NACK 0x29
#define I2C_CMD_IACK 0x01
#define KEMPLD_I2C_FREQ_MAX 2700 /* 2.7 mHz */
#define KEMPLD_I2C_FREQ_STD 100 /* 100 kHz */
#define EIO 5
#define ENXIO 6
#define EAGAIN 11
#define EBUSY 16
#define ETIMEDOUT 110
enum kempld_i2c_state {
STATE_DONE = 0,
STATE_INIT,
STATE_ADDR,
STATE_ADDR10,
STATE_START,
STATE_WRITE,
STATE_READ,
STATE_ERROR,
};
struct kempld_i2c_data {
const struct i2c_msg *msg;
size_t pos;
size_t nmsgs;
enum kempld_i2c_state state;
};
/*
* kempld_get_mutex must be called prior to calling this function.
*/
static int kempld_i2c_process(struct kempld_i2c_data *const i2c)
{
u8 stat = kempld_read8(KEMPLD_I2C_STAT);
const struct i2c_msg *msg = i2c->msg;
u8 addr;
/* Ready? */
if (stat & I2C_STAT_TIP)
return -EBUSY;
if (i2c->state == STATE_DONE || i2c->state == STATE_ERROR) {
/* Stop has been sent */
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_IACK);
if (i2c->state == STATE_ERROR)
return -EIO;
return 0;
}
/* Error? */
if (stat & I2C_STAT_ARBLOST) {
i2c->state = STATE_ERROR;
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_STOP);
return -EAGAIN;
}
if (i2c->state == STATE_INIT) {
if (stat & I2C_STAT_BUSY)
return -EBUSY;
i2c->state = STATE_ADDR;
}
if (i2c->state == STATE_ADDR) {
/* 10 bit address? */
if (i2c->msg->flags & I2C_M_TEN) {
addr = 0xf0 | ((i2c->msg->slave >> 7) & 0x6);
i2c->state = STATE_ADDR10;
} else {
addr = (i2c->msg->slave << 1);
i2c->state = STATE_START;
}
/* Set read bit if necessary */
addr |= (i2c->msg->flags & I2C_M_RD) ? 1 : 0;
kempld_write8(KEMPLD_I2C_DATA, addr);
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_START);
return 0;
}
/* Second part of 10 bit addressing */
if (i2c->state == STATE_ADDR10) {
kempld_write8(KEMPLD_I2C_DATA, i2c->msg->slave & 0xff);
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_WRITE);
i2c->state = STATE_START;
return 0;
}
if (i2c->state == STATE_START || i2c->state == STATE_WRITE) {
i2c->state = (msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
if (stat & I2C_STAT_NACK) {
i2c->state = STATE_ERROR;
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_STOP);
return -ENXIO;
}
} else {
msg->buf[i2c->pos++] = kempld_read8(KEMPLD_I2C_DATA);
}
if (i2c->pos >= msg->len) {
i2c->nmsgs--;
i2c->msg++;
i2c->pos = 0;
msg = i2c->msg;
if (i2c->nmsgs) {
if (!(msg->flags & I2C_M_NOSTART)) {
i2c->state = STATE_ADDR;
return 0;
}
i2c->state = (msg->flags & I2C_M_RD)
? STATE_READ : STATE_WRITE;
} else {
i2c->state = STATE_DONE;
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_STOP);
return 0;
}
}
if (i2c->state == STATE_READ) {
kempld_write8(KEMPLD_I2C_CMD, i2c->pos == (msg->len - 1) ?
I2C_CMD_READ_NACK : I2C_CMD_READ_ACK);
} else {
kempld_write8(KEMPLD_I2C_DATA, msg->buf[i2c->pos++]);
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_WRITE);
}
return 0;
}
static int kempld_i2c_xfer(struct device *const dev,
const struct i2c_msg *const msgs,
const size_t num)
{
struct kempld_i2c_data i2c;
struct stopwatch sw;
int ret;
if (kempld_get_mutex(100) < 0)
return -ENXIO;
i2c.msg = msgs;
i2c.pos = 0;
i2c.nmsgs = num;
i2c.state = STATE_INIT;
/* Handle the transfer */
stopwatch_init_msecs_expire(&sw, 1000);
while (!stopwatch_expired(&sw)) {
ret = kempld_i2c_process(&i2c);
if (i2c.state == STATE_DONE || i2c.state == STATE_ERROR) {
if (i2c.state == STATE_DONE) {
printk(BIOS_SPEW, "kempld_i2c: Processed %zu segments.\n", num);
ret = 0;
} else {
printk(BIOS_INFO, "kempld_i2c: Transfer failed.\n");
}
goto _release;
}
if (ret == 0)
stopwatch_init_msecs_expire(&sw, 1000);
udelay(10);
}
i2c.state = STATE_ERROR;
ret = -ETIMEDOUT;
printk(BIOS_INFO, "kempld_i2c: Transfer failed.\n");
_release:
kempld_release_mutex();
return ret;
}
static const struct i2c_bus_operations kempld_i2c_bus_ops = {
.transfer = kempld_i2c_xfer,
};
static struct device_operations kempld_i2c_dev_ops = {
.scan_bus = &scan_smbus,
.ops_i2c_bus = &kempld_i2c_bus_ops,
};
void kempld_i2c_device_init(struct device *const dev)
{
u16 prescale_corr;
long prescale;
u8 ctrl;
u8 stat;
u8 cfg;
if (kempld_get_mutex(100) < 0)
return;
/* Make sure the device is disabled */
ctrl = kempld_read8(KEMPLD_I2C_CTRL);
ctrl &= ~(I2C_CTRL_EN | I2C_CTRL_IEN);
kempld_write8(KEMPLD_I2C_CTRL, ctrl);
const u8 spec_major = KEMPLD_SPEC_GET_MAJOR(kempld_read8(KEMPLD_SPEC));
if (spec_major == 1)
prescale = KEMPLD_CLK / (KEMPLD_I2C_FREQ_STD * 5) - 1000;
else
prescale = KEMPLD_CLK / (KEMPLD_I2C_FREQ_STD * 4) - 3000;
if (prescale < 0)
prescale = 0;
/* Round to the best matching value */
prescale_corr = prescale / 1000;
if (prescale % 1000 >= 500)
prescale_corr++;
kempld_write8(KEMPLD_I2C_PRELOW, prescale_corr & 0xff);
kempld_write8(KEMPLD_I2C_PREHIGH, prescale_corr >> 8);
/* Disable I2C bus output on GPIO pins */
cfg = kempld_read8(KEMPLD_CFG);
cfg &= ~KEMPLD_CFG_GPIO_I2C_MUX;
kempld_write8(KEMPLD_CFG, cfg);
/* Enable the device */
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_IACK);
ctrl |= I2C_CTRL_EN;
kempld_write8(KEMPLD_I2C_CTRL, ctrl);
stat = kempld_read8(KEMPLD_I2C_STAT);
if (stat & I2C_STAT_BUSY)
kempld_write8(KEMPLD_I2C_CMD, I2C_CMD_STOP);
dev->ops = &kempld_i2c_dev_ops;
kempld_release_mutex();
}
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