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a84c11e16d
Recent changes to cdns_spi_irq introduced some issues.
Firstly, when writing the end of a longer transaction, the code in
cdns_spi_irq will write data into the TX FIFO, then immediately
fall into the if (!xspi->tx_bytes) path and attempt to read data
from the RX FIFO. However this required waiting for the TX FIFO to
empty before the RX data was ready.
Secondly, the variable trans_cnt is now rather inaccurately named
since in cases, where the watermark is set to 1, trans_cnt will be
1 but the count of bytes transferred would be much longer.
Finally, when setting up the transaction we set the watermark to 50%
of the FIFO if the transaction is great than 50% of the FIFO. However,
there is no need to split a tranaction that is smaller than the
whole FIFO, so anything up to the FIFO size can be done in a single
transaction.
Tidy up the code a little, to avoid repeatedly calling
cdns_spi_read_rx_fifo with a count of 1, and correct the three issues
noted above.
Fixes: b1b90514ea ("spi: spi-cadence: Add support for Slave mode")
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com
Link: https://lore.kernel.org/r/20230509164153.3907694-1-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org
Linux kernel
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