diff options
| author | Lukas Wunner <lukas@wunner.de> | 2019-07-03 12:29:31 +0200 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2019-07-24 19:44:59 +0100 |
| commit | 8d8bef50365847134b51c1ec46786bc2873e4e47 (patch) | |
| tree | 0399a7bd5c7623fb0f49d7e0b2c99ec0e547f66d /drivers/spi | |
| parent | 1274204542f683e1d8491ebe9cc86284d5a8ebcc (diff) | |
spi: bcm2835: Fix 3-wire mode if DMA is enabled
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>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/spi-bcm2835.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 6f243a90c844..840b1b8ff3dc 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -834,7 +834,8 @@ static int bcm2835_spi_transfer_one(struct spi_controller *ctlr, 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 != ctlr->dummy_rx) cs |= BCM2835_SPI_CS_REN; else cs &= ~BCM2835_SPI_CS_REN; |