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authorLukas Wunner <lukas@wunner.de>2019-07-03 12:29:31 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-08-09 17:52:35 +0200
commit48fcdaba7b0d31e59f01ce96b4f53e8149787d1a (patch)
parentebda41dd170fd160e44f97d7a2a215ae9d0009b1 (diff)
spi: bcm2835: Fix 3-wire mode if DMA is enabled
commit 8d8bef50365847134b51c1ec46786bc2873e4e47 upstream. Commit 6935224da248 ("spi: bcm2835: enable support of 3-wire mode") added 3-wire support to the BCM2835 SPI driver by setting the REN bit (Read Enable) in the CS register when receiving data. The REN bit puts the transmitter in high-impedance state. The driver recognizes that data is to be received by checking whether the rx_buf of a transfer is non-NULL. Commit 3ecd37edaa2a ("spi: bcm2835: enable dma modes for transfers meeting certain conditions") subsequently broke 3-wire support because it set the SPI_MASTER_MUST_RX flag which causes spi_map_msg() to replace rx_buf with a dummy buffer if it is NULL. As a result, rx_buf is *always* non-NULL if DMA is enabled. Reinstate 3-wire support by not only checking whether rx_buf is non-NULL, but also checking that it is not the dummy buffer. Fixes: 3ecd37edaa2a ("spi: bcm2835: enable dma modes for transfers meeting certain conditions") Reported-by: Nuno Sá <nuno.sa@analog.com> Signed-off-by: Lukas Wunner <lukas@wunner.de> Cc: stable@vger.kernel.org # v4.2+ Cc: Martin Sperl <kernel@martin.sperl.org> Acked-by: Stefan Wahren <wahrenst@gmx.net> Link: https://lore.kernel.org/r/328318841455e505370ef8ecad97b646c033dc8a.1562148527.git.lukas@wunner.de Signed-off-by: Mark Brown <broonie@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 25abf2d1732a..eab27d41ba83 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -554,7 +554,8 @@ static int bcm2835_spi_transfer_one(struct spi_master *master,
bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);
/* handle all the 3-wire mode */
- if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf))
+ if (spi->mode & SPI_3WIRE && tfr->rx_buf &&
+ tfr->rx_buf != master->dummy_rx)
cs |= BCM2835_SPI_CS_REN;
cs &= ~BCM2835_SPI_CS_REN;