i2c: pasemi: Wait for write xfers to finish

stable inclusion
from stable-v5.10.112
commit 84837f43e56fc2594f07a49399667c467de527a3
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5HL0X

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=84837f43e56fc2594f07a49399667c467de527a3

--------------------------------

commit bd8963e6 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: beb58aa3 ("i2c: PA Semi SMBus driver")
Signed-off-by: NMartin Povišer <povik+lin@cutebit.org>
Reviewed-by: NSven Peter <sven@svenpeter.dev>
Signed-off-by: NWolfram Sang <wsa@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

drivers/i2c/busses/i2c-pasemi.c

@@ -137,6 +137,12 @@ static int pasemi_i2c_xfer_msg(struct i2c_adapter *adapter,
 
 		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;