diff options
Diffstat (limited to 'drivers/net/sfc/i2c-direct.c')
| -rw-r--r-- | drivers/net/sfc/i2c-direct.c | 381 |
1 files changed, 381 insertions, 0 deletions
diff --git a/drivers/net/sfc/i2c-direct.c b/drivers/net/sfc/i2c-direct.c new file mode 100644 index 0000000..b6c62d0e --- /dev/null +++ b/drivers/net/sfc/i2c-direct.c @@ -0,0 +1,381 @@ +/**************************************************************************** + * 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)) +} |
