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Implement board-level I2C arbitration

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Add a way for boards to permit or deny access to the I2C port. This
works in a board-specific manner.

All I2C master traffic requires that board_i2c_claim() be called
first. A dummy function is provided for boards which do not require
this.

BUG=chrome-os-partner:10888
TEST=manual:
build for all boards
boot on snow (cannot test i2c as it is broken)

Change-Id: I786d4ae17f1d798faf13b303b5389679fb6720cb
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/26141
This commit is contained in:
Simon Glass
2012-06-26 14:19:54 -07:00
committed by Gerrit
parent 7e50e844a3
commit 7bcf881bd6
2 changed files with 55 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

27
chip/stm32/i2c.c
View File

@@ -70,6 +70,23 @@ static inline void disable_ack(int port)
STM32_I2C_CR1(port) &= ~(1 << 10);
}
int __board_i2c_claim(int port)
{
return 0;
}
int board_i2c_claim(int port)
__attribute__((weak, alias("__board_i2c_claim")));
void __board_i2c_release(int port)
{
}
void board_i2c_release(int port)
__attribute__((weak, alias("__board_i2c_release")));
static int wait_tx(int port)
{
static timestamp_t deadline;
@@ -554,6 +571,12 @@ static int i2c_xfer(int port, int slave_addr, uint8_t *out, int out_bytes,
ASSERT(in || !in_bytes);
mutex_lock(&i2c_mutex);
if (board_i2c_claim(port)) {
rv = EC_ERROR_BUSY;
goto err_claim;
}
disable_i2c_interrupt(port);
rv = i2c_master_transmit(port, slave_addr, out, out_bytes,
@@ -563,6 +586,10 @@ static int i2c_xfer(int port, int slave_addr, uint8_t *out, int out_bytes,
handle_i2c_error(port, rv);
enable_i2c_interrupt(port);
board_i2c_release(port);
err_claim:
mutex_unlock(&i2c_mutex);
return rv;

28
include/i2c.h
View File

@@ -48,4 +48,32 @@ int i2c_write8(int port, int slave_addr, int offset, int data);
int i2c_read_string(int port, int slave_addr, int offset, uint8_t *data,
int len);
/**
* Claim an I2C port for use in master mode
*
* If this function succeed, then you must later call board_i2c_release()
* to release the claim.
*
* This function may optionally be implemented by a board file. If provided
* then it should check the port number and arbitrate as needed.
*
* This function will not be called to claim an already-claimed port.
*
* @param port Port to claim (0 for first, 1 for second, etc.)
* @return 0 if claimed successfully, -1 if it is in use
*/
int board_i2c_claim(int port);
/**
* Release an I2C port (after previously being claimed)
*
* This function may optionally be implemented by a board file. If provided
* then it should check the port number and arbitrate as needed.
*
* This function will not be called to release an already-released port.
*
* @param port Port to claim (0 for first, 1 for second, etc.)
*/
void board_i2c_release(int port);
#endif /* __CROS_EC_I2C_H */