From 44a5f423e70374e5b42cecd85e78f2d79334e0f2 Mon Sep 17 00:00:00 2001 From: Maxime Chevallier Date: Wed, 17 Jan 2018 17:15:25 +0100 Subject: spi: a3700: Clear DATA_OUT when performing a read When performing a read using FIFO mode, the spi controller shifts out the last 2 bytes that were written in a previous transfer on MOSI. This undocumented behaviour can cause devices to misinterpret the transfer, so we explicitly clear the WFIFO before each read. This behaviour was noticed on EspressoBin. Signed-off-by: Maxime Chevallier Signed-off-by: Mark Brown --- drivers/spi/spi-armada-3700.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'drivers/spi/spi-armada-3700.c') diff --git a/drivers/spi/spi-armada-3700.c b/drivers/spi/spi-armada-3700.c index 77fe55ce790c..4857b0119556 100644 --- a/drivers/spi/spi-armada-3700.c +++ b/drivers/spi/spi-armada-3700.c @@ -607,6 +607,11 @@ static int a3700_spi_transfer_one(struct spi_master *master, a3700_spi_header_set(a3700_spi); if (xfer->rx_buf) { + /* Clear WFIFO, since it's last 2 bytes are shifted out during + * a read operation + */ + spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG, 0); + /* Set read data length */ spireg_write(a3700_spi, A3700_SPI_IF_DIN_CNT_REG, a3700_spi->buf_len); -- cgit