[PATCH] spi: spi-cadence: Reverse the order of interleaved write and read operations

[PATCH] spi: spi-cadence: Reverse the order of interleaved write and read operations

[Amit Kumar Mahapatra]

In the existing implementation, when executing interleaved write and read
operations in the ISR for a transfer length greater than the FIFO size,
the TXFIFO write precedes the RXFIFO read. Consequently, the initially
received data in the RXFIFO is pushed out and lost, leading to a failure
in data integrity. To address this issue, reverse the order of interleaved
operations and conduct the RXFIFO read followed by the TXFIFO write.

Fixes: 6afe2ae8dc48 ("spi: spi-cadence: Interleave write of TX and read of RX FIFO")
Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com>
---
BRANCH: for-next
---
 drivers/spi/spi-cadence.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index a50eb4db79de..e5140532071d 100644
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -317,6 +317,15 @@ static void cdns_spi_process_fifo(struct cdns_spi *xspi, int ntx, int nrx)
 	xspi->rx_bytes -= nrx;
 
 	while (ntx || nrx) {
+		if (nrx) {
+			u8 data = cdns_spi_read(xspi, CDNS_SPI_RXD);
+
+			if (xspi->rxbuf)
+				*xspi->rxbuf++ = data;
+
+			nrx--;
+		}
+
 		if (ntx) {
 			if (xspi->txbuf)
 				cdns_spi_write(xspi, CDNS_SPI_TXD, *xspi->txbuf++);
@@ -326,14 +335,6 @@ static void cdns_spi_process_fifo(struct cdns_spi *xspi, int ntx, int nrx)
 			ntx--;
 		}
 
-		if (nrx) {
-			u8 data = cdns_spi_read(xspi, CDNS_SPI_RXD);
-
-			if (xspi->rxbuf)
-				*xspi->rxbuf++ = data;
-
-			nrx--;
-		}
 	}
 }
 
-- 
2.17.1

Re: [PATCH] spi: spi-cadence: Reverse the order of interleaved write and read operations

[Mark Brown]

On Mon, 18 Dec 2023 14:36:52 +0530, Amit Kumar Mahapatra wrote:
> In the existing implementation, when executing interleaved write and read
> operations in the ISR for a transfer length greater than the FIFO size,
> the TXFIFO write precedes the RXFIFO read. Consequently, the initially
> received data in the RXFIFO is pushed out and lost, leading to a failure
> in data integrity. To address this issue, reverse the order of interleaved
> operations and conduct the RXFIFO read followed by the TXFIFO write.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: spi-cadence: Reverse the order of interleaved write and read operations
      commit: 8715c23b6540d142b955efe64f91b8bc2d3cf623

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark