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| author | Maxime Chevallier <maxime.chevallier@smile.fr> | 2018-01-17 17:15:25 +0100 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2018-01-18 10:59:12 +0000 |
| commit | 44a5f423e70374e5b42cecd85e78f2d79334e0f2 (patch) | |
| tree | ac17c518f5357f051350af2833675af9cb913182 /drivers/spi | |
| parent | 4fbd8d194f06c8a3fd2af1ce560ddb31f7ec8323 (diff) | |
| download | blackbird-op-linux-44a5f423e70374e5b42cecd85e78f2d79334e0f2.tar.gz blackbird-op-linux-44a5f423e70374e5b42cecd85e78f2d79334e0f2.zip | |
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>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/spi-armada-3700.c | 5 |
1 files changed, 5 insertions, 0 deletions
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); |
