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We have > seen xiic_process() run with TX_ERROR set but RX_FULL not yet set, > while the RX FIFO already holds all of the remaining bytes of the > message. > > xiic_process() treats TX_ERROR without RX_FULL as an error, so in this > case it reinitializes the core, the data in the FIFO is lost, and the > read returns -EIO even though it finished on the bus. The next read on > the same adapter can also return stale data without reporting an error. > > Fix this by checking the RX FIFO in the error path. If the message is > a read, there was no arbitration loss, and the FIFO has all of the > remaining bytes, handle it the same way as RX_FULL and complete the > message. Since IISR is toggle-on-write, only clear RX_FULL if it was > actually set. > > We found this on a system with several AXI IIC controllers in one PCIe > FPGA that share an interrupt. It only happens when at least two > controllers are busy at the same time. With 12 QSFP-DD modules being > read in parallel for 480 seconds, the failures went from 2083 -EIO and > 1158 reads with wrong data (out of 11.2M reads) to none. > > Fixes: e1d5b6598cdc ("i2c: Add support for Xilinx XPS IIC Bus Interface") > Cc: stable@vger.kernel.org > Signed-off-by: Siddarth Chilukuri > --- > I tested this on hardware with the 6.11 kernel we found the problem > on. On mainline it is compile-tested only. > --- > drivers/i2c/busses/i2c-xiic.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) Shubhrajyoti please test and review. Thanks, Michal