[ Upstream commit c842749ea1d32513f9e603c074d60d7aa07cb2ef ]
Commit 71abd29057cb ("spi: imx: Add support for SPI Slave mode") added an RX FIFO flush before start of a transfer. In slave mode, the master may have sent more data than expected and this data will still be in the RX FIFO at the start of the next transfer, and so needs to be flushed.
However, the code to do the flush was accidentally saving this data into the previous transfer's RX buffer, clobbering the contents of whatever followed that buffer.
Change it to empty the FIFO and throw away the data. Every one of the RX functions for the different eCSPI versions and modes reads the RX FIFO data using the same readl() call, so just use that, rather than using the spi_imx->rx function pointer and making sure all the different rx functions have a working "throw away" mode.
There is another issue, which affects master mode when switching from DMA to PIO. There can be extra data in the RX FIFO which triggers this flush code, causing memory corruption in the same manner. I don't know why this data is unexpectedly in the FIFO. It's likely there is a different bug or erratum responsible for that. But regardless of that, I think this is proper fix the for bug at hand here.
Fixes: 71abd29057cb ("spi: imx: Add support for SPI Slave mode") Cc: Jiada Wang jiada_wang@mentor.com Cc: Fabio Estevam festevam@gmail.com Cc: Stefan Agner stefan@agner.ch Cc: Shawn Guo shawnguo@kernel.org Signed-off-by: Trent Piepho tpiepho@impinj.com Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/spi/spi-imx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index 08dd3a31a3e5f..5b6f3655c366a 100644 --- a/drivers/spi/spi-imx.c +++ b/drivers/spi/spi-imx.c @@ -1427,7 +1427,7 @@ static int spi_imx_transfer(struct spi_device *spi,
/* flush rxfifo before transfer */ while (spi_imx->devtype_data->rx_available(spi_imx)) - spi_imx->rx(spi_imx); + readl(spi_imx->base + MXC_CSPIRXDATA);
if (spi_imx->slave_mode) return spi_imx_pio_transfer_slave(spi, transfer);