diff options
authorGrygorii Strashko <grygorii.strashko@ti.com>2014-12-01 17:34:04 +0200
committerWolfram Sang <wsa@the-dreams.de>2014-12-04 19:25:31 +0100
commit9ea359f7314132cbcb5a502d2d8ef095be1f45e4 (patch)
parent7cc78f8fa02c2485104b86434acbc1538a3bd807 (diff)
i2c: davinci: generate STP always when NACK is received
According to I2C specification the NACK should be handled as follows: "When SDA remains HIGH during this ninth clock pulse, this is defined as the Not Acknowledge signal. The master can then generate either a STOP condition to abort the transfer, or a repeated START condition to start a new transfer." [I2C spec Rev. 6, 3.1.6: http://www.nxp.com/documents/user_manual/UM10204.pdf] Currently the Davinci i2c driver interrupts the transfer on receipt of a NACK but fails to send a STOP in some situations and so makes the bus stuck until next I2C IP reset (idle/enable). For example, the issue will happen during SMBus read transfer which consists from two i2c messages write command/address and read data: S Slave Address Wr A Command Code A Sr Slave Address Rd A D1..Dn A P <--- write -----------------------> <--- read ---------------------> The I2C client device will send NACK if it can't recognize "Command Code" and it's expected from I2C master to generate STP in this case. But now, Davinci i2C driver will just exit with -EREMOTEIO and STP will not be generated. Hence, fix it by generating Stop condition (STP) always when NACK is received. This patch fixes Davinci I2C in the same way it was done for OMAP I2C commit cda2109a26eb ("i2c: omap: query STP always when NACK is received"). Reviewed-by: Uwe Kleine-K├Ânig <u.kleine-koenig@pengutronix.de> Reported-by: Hein Tibosch <hein_tibosch@yahoo.es> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de> Cc: stable@kernel.org
1 files changed, 3 insertions, 5 deletions
diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index d15b7c9b9219..01f0cd87a4a5 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -407,11 +407,9 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
if (dev->cmd_err & DAVINCI_I2C_STR_NACK) {
if (msg->flags & I2C_M_IGNORE_NAK)
return msg->len;
- if (stop) {
- w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
- davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w);
- }
+ w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w);
return -EREMOTEIO;
return -EIO;