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spi: bcm2835: Fix 3-wire mode if DMA is enabled
commit8d8bef5036
upstream. Commit6935224da2
("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. Commit3ecd37edaa
("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:3ecd37edaa
("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>
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1 changed files with 2 additions and 1 deletions
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@ -554,7 +554,8 @@ static int bcm2835_spi_transfer_one(struct spi_master *master,
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bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);
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/* handle all the 3-wire mode */
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if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf))
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if (spi->mode & SPI_3WIRE && tfr->rx_buf &&
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tfr->rx_buf != master->dummy_rx)
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cs |= BCM2835_SPI_CS_REN;
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else
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cs &= ~BCM2835_SPI_CS_REN;
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