From: Martin Povišer povik+lin@cutebit.org
commit bd8963e602c77adc76dbbbfc3417c3cf14fed76b upstream.
Wait for completion of write transfers before returning from the driver. At first sight it may seem advantageous to leave write transfers queued for the controller to carry out on its own time, but there's a couple of issues with it:
* Driver doesn't check for FIFO space.
* The queued writes can complete while the driver is in its I2C read transfer path which means it will get confused by the raising of XEN (the 'transaction ended' signal). This can cause a spurious ENODATA error due to premature reading of the MRXFIFO register.
Adding the wait fixes some unreliability issues with the driver. There's some efficiency cost to it (especially with pasemi_smb_waitready doing its polling), but that will be alleviated once the driver receives interrupt support.
Fixes: beb58aa39e6e ("i2c: PA Semi SMBus driver") Signed-off-by: Martin Povišer povik+lin@cutebit.org Reviewed-by: Sven Peter sven@svenpeter.dev Signed-off-by: Wolfram Sang wsa@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/i2c/busses/i2c-pasemi-core.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/i2c/busses/i2c-pasemi-core.c +++ b/drivers/i2c/busses/i2c-pasemi-core.c @@ -137,6 +137,12 @@ static int pasemi_i2c_xfer_msg(struct i2
TXFIFO_WR(smbus, msg->buf[msg->len-1] | (stop ? MTXFIFO_STOP : 0)); + + if (stop) { + err = pasemi_smb_waitready(smbus); + if (err) + goto reset_out; + } }
return 0;