Unverified Commit 44a5f423 authored Jan 17, 2018 by Maxime Chevallier Committed by Mark Brown Jan 18, 2018

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 <maxime.chevallier@smile.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>

parent 4fbd8d19

drivers/spi/spi-armada-3700.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -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);