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Add 8-bit I2C read/write functions.

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These provide 8-bit accesses to registers within an I2C device.

BUG=chrome-os-partner:7839
TEST=none

Testing will come when I start using them.

Change-Id: Ib53d3347253bccee93cb9c5da12db92970155d92
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
This commit is contained in:
Bill Richardson
2012-02-13 14:45:29 -08:00
parent 616c60e707
commit e5b17f9047
2 changed files with 65 additions and 0 deletions
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55
chip/lm4/i2c.c
View File

@@ -126,6 +126,61 @@ int i2c_write16(int port, int slave_addr, int offset, int data)
return wait_idle(port);
}
/* TODO:(crosbug.com/p/8026) combine common functions to save space */
int i2c_read8(int port, int slave_addr, int offset, int* data)
{
int rv;
*data = 0;
/* Transmit the offset address to the slave; leave the master in
* transmit state. */
LM4_I2C_MSA(port) = slave_addr & 0xff;
LM4_I2C_MDR(port) = offset & 0xff;
LM4_I2C_MCS(port) = 0x03;
rv = wait_idle(port);
if (rv)
return rv;
/* Send repeated start followed by receive and stop */
LM4_I2C_MSA(port) = (slave_addr & 0xff) | 0x01;
LM4_I2C_MCS(port) = 0x07; /* NOTE: datasheet suggests 0x0b, but
* 0x07 with the change in direction
* flips it to a RECEIVE and STOP.
* I think.
*/
rv = wait_idle(port);
if (rv)
return rv;
/* Read the byte */
*data = LM4_I2C_MDR(port) & 0xff;
return EC_SUCCESS;
}
int i2c_write8(int port, int slave_addr, int offset, int data)
{
int rv;
/* Transmit the offset address to the slave; leave the master in
* transmit state. */
LM4_I2C_MDR(port) = offset & 0xff;
LM4_I2C_MSA(port) = slave_addr & 0xff;
LM4_I2C_MCS(port) = 0x03;
rv = wait_idle(port);
if (rv)
return rv;
/* Send repeated start followed by transmit and stop */
LM4_I2C_MDR(port) = data & 0xff;
LM4_I2C_MCS(port) = 0x05;
return wait_idle(port);
}
/*****************************************************************************/
/* Interrupt handlers */

10
include/i2c.h
View File

@@ -26,4 +26,14 @@ int i2c_read16(int port, int slave_addr, int offset, int* data);
* space. */
int i2c_write16(int port, int slave_addr, int offset, int data);
/* Reads an 8-bit register from the slave at 8-bit slave address
* <slaveaddr>, at the specified 8-bit <offset> in the slave's address
* space. */
int i2c_read8(int port, int slave_addr, int offset, int* data);
/* Writes an 8-bit register to the slave at 8-bit slave address
* <slaveaddr>, at the specified 8-bit <offset> in the slave's address
* space. */
int i2c_write8(int port, int slave_addr, int offset, int data);
#endif /* __CROS_EC_I2C_H */