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/****************************************************************************
* Driver for Solarflare Solarstorm network controllers and boards
* Copyright 2005 Fen Systems Ltd.
* Copyright 2006-2008 Solarflare Communications Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published
* by the Free Software Foundation, incorporated herein by reference.
*/
#include <linux/delay.h>
#include "net_driver.h"
#include "i2c-direct.h"
/*
* I2C data (SDA) and clock (SCL) line read/writes with appropriate
* delays.
*/
static inline void setsda(struct efx_i2c_interface *i2c, int state)
{
udelay(i2c->op->udelay);
i2c->sda = state;
i2c->op->setsda(i2c);
udelay(i2c->op->udelay);
}
static inline void setscl(struct efx_i2c_interface *i2c, int state)
{
udelay(i2c->op->udelay);
i2c->scl = state;
i2c->op->setscl(i2c);
udelay(i2c->op->udelay);
}
static inline int getsda(struct efx_i2c_interface *i2c)
{
int sda;
udelay(i2c->op->udelay);
sda = i2c->op->getsda(i2c);
udelay(i2c->op->udelay);
return sda;
}
static inline int getscl(struct efx_i2c_interface *i2c)
{
int scl;
udelay(i2c->op->udelay);
scl = i2c->op->getscl(i2c);
udelay(i2c->op->udelay);
return scl;
}
/*
* I2C low-level protocol operations
*
*/
static inline void i2c_release(struct efx_i2c_interface *i2c)
{
EFX_WARN_ON_PARANOID(!i2c->scl);
EFX_WARN_ON_PARANOID(!i2c->sda);
/* Devices may time out if operations do not end */
setscl(i2c, 1);
setsda(i2c, 1);
EFX_BUG_ON_PARANOID(getsda(i2c) != 1);
EFX_BUG_ON_PARANOID(getscl(i2c) != 1);
}
static inline void i2c_start(struct efx_i2c_interface *i2c)
{
/* We may be restarting immediately after a {send,recv}_bit,
* so SCL will not necessarily already be high.
*/
EFX_WARN_ON_PARANOID(!i2c->sda);
setscl(i2c, 1);
setsda(i2c, 0);
setscl(i2c, 0);
setsda(i2c, 1);
}
static inline void i2c_send_bit(struct efx_i2c_interface *i2c, int bit)
{
EFX_WARN_ON_PARANOID(i2c->scl != 0);
setsda(i2c, bit);
setscl(i2c, 1);
setscl(i2c, 0);
setsda(i2c, 1);
}
static inline int i2c_recv_bit(struct efx_i2c_interface *i2c)
{
int bit;
EFX_WARN_ON_PARANOID(i2c->scl != 0);
EFX_WARN_ON_PARANOID(!i2c->sda);
setscl(i2c, 1);
bit = getsda(i2c);
setscl(i2c, 0);
return bit;
}
static inline void i2c_stop(struct efx_i2c_interface *i2c)
{
EFX_WARN_ON_PARANOID(i2c->scl != 0);
setsda(i2c, 0);
setscl(i2c, 1);
setsda(i2c, 1);
}
/*
* I2C mid-level protocol operations
*
*/
/* Sends a byte via the I2C bus and checks for an acknowledgement from
* the slave device.
*/
static int i2c_send_byte(struct efx_i2c_interface *i2c, u8 byte)
{
int i;
/* Send byte */
for (i = 0; i < 8; i++) {
i2c_send_bit(i2c, !!(byte & 0x80));
byte <<= 1;
}
/* Check for acknowledgement from slave */
return (i2c_recv_bit(i2c) == 0 ? 0 : -EIO);
}
/* Receives a byte via the I2C bus and sends ACK/NACK to the slave device. */
static u8 i2c_recv_byte(struct efx_i2c_interface *i2c, int ack)
{
u8 value = 0;
int i;
/* Receive byte */
for (i = 0; i < 8; i++)
value = (value << 1) | i2c_recv_bit(i2c);
/* Send ACK/NACK */
i2c_send_bit(i2c, (ack ? 0 : 1));
return value;
}
/* Calculate command byte for a read operation */
static inline u8 i2c_read_cmd(u8 device_id)
{
return ((device_id << 1) | 1);
}
/* Calculate command byte for a write operation */
static inline u8 i2c_write_cmd(u8 device_id)
{
return ((device_id << 1) | 0);
}
int efx_i2c_check_presence(struct efx_i2c_interface *i2c, u8 device_id)
{
int rc;
/* If someone is driving the bus low we just give up. */
if (getsda(i2c) == 0 || getscl(i2c) == 0) {
EFX_ERR(i2c->efx, "%s someone is holding the I2C bus low."
" Giving up.\n", __func__);
return -EFAULT;
}
/* Pretend to initiate a device write */
i2c_start(i2c);
rc = i2c_send_byte(i2c, i2c_write_cmd(device_id));
if (rc)
goto out;
out:
i2c_stop(i2c);
i2c_release(i2c);
return rc;
}
/* This performs a fast read of one or more consecutive bytes from an
* I2C device. Not all devices support consecutive reads of more than
* one byte; for these devices use efx_i2c_read() instead.
*/
int efx_i2c_fast_read(struct efx_i2c_interface *i2c,
u8 device_id, u8 offset, u8 *data, unsigned int len)
{
int i;
int rc;
EFX_WARN_ON_PARANOID(getsda(i2c) != 1);
EFX_WARN_ON_PARANOID(getscl(i2c) != 1);
EFX_WARN_ON_PARANOID(data == NULL);
EFX_WARN_ON_PARANOID(len < 1);
/* Select device and starting offset */
i2c_start(i2c);
rc = i2c_send_byte(i2c, i2c_write_cmd(device_id));
if (rc)
goto out;
rc = i2c_send_byte(i2c, offset);
if (rc)
goto out;
/* Read data from device */
i2c_start(i2c);
rc = i2c_send_byte(i2c, i2c_read_cmd(device_id));
if (rc)
goto out;
for (i = 0; i < (len - 1); i++)
/* Read and acknowledge all but the last byte */
data[i] = i2c_recv_byte(i2c, 1);
/* Read last byte with no acknowledgement */
data[i] = i2c_recv_byte(i2c, 0);
out:
i2c_stop(i2c);
i2c_release(i2c);
return rc;
}
/* This performs a fast write of one or more consecutive bytes to an
* I2C device. Not all devices support consecutive writes of more
* than one byte; for these devices use efx_i2c_write() instead.
*/
int efx_i2c_fast_write(struct efx_i2c_interface *i2c,
u8 device_id, u8 offset,
const u8 *data, unsigned int len)
{
int i;
int rc;
EFX_WARN_ON_PARANOID(getsda(i2c) != 1);
EFX_WARN_ON_PARANOID(getscl(i2c) != 1);
EFX_WARN_ON_PARANOID(len < 1);
/* Select device and starting offset */
i2c_start(i2c);
rc = i2c_send_byte(i2c, i2c_write_cmd(device_id));
if (rc)
goto out;
rc = i2c_send_byte(i2c, offset);
if (rc)
goto out;
/* Write data to device */
for (i = 0; i < len; i++) {
rc = i2c_send_byte(i2c, data[i]);
if (rc)
goto out;
}
out:
i2c_stop(i2c);
i2c_release(i2c);
return rc;
}
/* I2C byte-by-byte read */
int efx_i2c_read(struct efx_i2c_interface *i2c,
u8 device_id, u8 offset, u8 *data, unsigned int len)
{
int rc;
/* i2c_fast_read with length 1 is a single byte read */
for (; len > 0; offset++, data++, len--) {
rc = efx_i2c_fast_read(i2c, device_id, offset, data, 1);
if (rc)
return rc;
}
return 0;
}
/* I2C byte-by-byte write */
int efx_i2c_write(struct efx_i2c_interface *i2c,
u8 device_id, u8 offset, const u8 *data, unsigned int len)
{
int rc;
/* i2c_fast_write with length 1 is a single byte write */
for (; len > 0; offset++, data++, len--) {
rc = efx_i2c_fast_write(i2c, device_id, offset, data, 1);
if (rc)
return rc;
mdelay(i2c->op->mdelay);
}
return 0;
}
/* This is just a slightly neater wrapper round efx_i2c_fast_write
* in the case where the target doesn't take an offset
*/
int efx_i2c_send_bytes(struct efx_i2c_interface *i2c,
u8 device_id, const u8 *data, unsigned int len)
{
return efx_i2c_fast_write(i2c, device_id, data[0], data + 1, len - 1);
}
/* I2C receiving of bytes - does not send an offset byte */
int efx_i2c_recv_bytes(struct efx_i2c_interface *i2c, u8 device_id,
u8 *bytes, unsigned int len)
{
int i;
int rc;
EFX_WARN_ON_PARANOID(getsda(i2c) != 1);
EFX_WARN_ON_PARANOID(getscl(i2c) != 1);
EFX_WARN_ON_PARANOID(len < 1);
/* Select device */
i2c_start(i2c);
/* Read data from device */
rc = i2c_send_byte(i2c, i2c_read_cmd(device_id));
if (rc)
goto out;
for (i = 0; i < (len - 1); i++)
/* Read and acknowledge all but the last byte */
bytes[i] = i2c_recv_byte(i2c, 1);
/* Read last byte with no acknowledgement */
bytes[i] = i2c_recv_byte(i2c, 0);
out:
i2c_stop(i2c);
i2c_release(i2c);
return rc;
}
/* SMBus and some I2C devices will time out if the I2C clock is
* held low for too long. This is most likely to happen in virtualised
* systems (when the entire domain is descheduled) but could in
* principle happen due to preemption on any busy system (and given the
* potential length of an I2C operation turning preemption off is not
* a sensible option). The following functions deal with the failure by
* retrying up to a fixed number of times.
*/
#define I2C_MAX_RETRIES (10)
/* The timeout problem will result in -EIO. If the wrapped function
* returns any other error, pass this up and do not retry. */
#define RETRY_WRAPPER(_f) \
int retries = I2C_MAX_RETRIES; \
int rc; \
while (retries) { \
rc = _f; \
if (rc != -EIO) \
return rc; \
retries--; \
} \
return rc; \
int efx_i2c_check_presence_retry(struct efx_i2c_interface *i2c, u8 device_id)
{
RETRY_WRAPPER(efx_i2c_check_presence(i2c, device_id))
}
int efx_i2c_read_retry(struct efx_i2c_interface *i2c,
u8 device_id, u8 offset, u8 *data, unsigned int len)
{
RETRY_WRAPPER(efx_i2c_read(i2c, device_id, offset, data, len))
}
int efx_i2c_write_retry(struct efx_i2c_interface *i2c,
u8 device_id, u8 offset, const u8 *data, unsigned int len)
{
RETRY_WRAPPER(efx_i2c_write(i2c, device_id, offset, data, len))
}
|
