path: root/drivers
diff options
authorJon Povey <jon.povey@racelogic.co.uk>2010-09-17 12:02:11 +0900
committerBen Dooks <ben-linux@fluff.org>2010-09-28 00:05:08 +0100
commit4bba0fd8d1c6d405df666e2573e1a1f917098be0 (patch)
treeaf3128819f126fc9333e7883af04952badef6ee6 /drivers
parentcc33e54290ed845904dac4b047934207738f0205 (diff)
i2c-davinci: Fix race when setting up for TX
When setting up to transmit, a race exists between the ISR and i2c_davinci_xfer_msg() trying to load the first byte and adjust counters. This is mostly visible for transmits > 1 byte long. The hardware starts sending immediately that MDR is loaded. IMR trickery doesn't work because if we start sending, finish the first byte and an XRDY event occurs before we load IMR to unmask it, we never get an interrupt, and we timeout. Move the MDR load after DXR,IMR loads to avoid this race without locking. Tested on DM355 connected to Techwell TW2836 and Wolfson WM8985 Signed-off-by: Jon Povey <jon.povey@racelogic.co.uk> Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Diffstat (limited to 'drivers')
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index 2222c87876b..b8feac5f2ef 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -357,9 +357,6 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
dev->terminate = 0;
- /* write the data into mode register */
- davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
* First byte should be set here, not after interrupt,
* because transmit-data-ready interrupt can come before
@@ -371,6 +368,9 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
+ /* write the data into mode register; start transmitting */
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
r = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
if (r == 0) {