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https://github.com/Ysurac/openmptcprouter.git
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56 lines
2.3 KiB
Diff
56 lines
2.3 KiB
Diff
From 48fcdaba7b0d31e59f01ce96b4f53e8149787d1a Mon Sep 17 00:00:00 2001
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From: Lukas Wunner <lukas@wunner.de>
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Date: Wed, 3 Jul 2019 12:29:31 +0200
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Subject: [PATCH 812/826] spi: bcm2835: Fix 3-wire mode if DMA is enabled
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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commit 8d8bef50365847134b51c1ec46786bc2873e4e47 upstream.
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Commit 6935224da248 ("spi: bcm2835: enable support of 3-wire mode")
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added 3-wire support to the BCM2835 SPI driver by setting the REN bit
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(Read Enable) in the CS register when receiving data. The REN bit puts
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the transmitter in high-impedance state. The driver recognizes that
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data is to be received by checking whether the rx_buf of a transfer is
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non-NULL.
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Commit 3ecd37edaa2a ("spi: bcm2835: enable dma modes for transfers
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meeting certain conditions") subsequently broke 3-wire support because
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it set the SPI_MASTER_MUST_RX flag which causes spi_map_msg() to replace
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rx_buf with a dummy buffer if it is NULL. As a result, rx_buf is
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*always* non-NULL if DMA is enabled.
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Reinstate 3-wire support by not only checking whether rx_buf is non-NULL,
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but also checking that it is not the dummy buffer.
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Fixes: 3ecd37edaa2a ("spi: bcm2835: enable dma modes for transfers meeting certain conditions")
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Reported-by: Nuno Sá <nuno.sa@analog.com>
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Signed-off-by: Lukas Wunner <lukas@wunner.de>
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Cc: stable@vger.kernel.org # v4.2+
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Cc: Martin Sperl <kernel@martin.sperl.org>
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Acked-by: Stefan Wahren <wahrenst@gmx.net>
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Link: https://lore.kernel.org/r/328318841455e505370ef8ecad97b646c033dc8a.1562148527.git.lukas@wunner.de
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Signed-off-by: Mark Brown <broonie@kernel.org>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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drivers/spi/spi-bcm2835.c | 3 ++-
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1 file changed, 2 insertions(+), 1 deletion(-)
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diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
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index 25abf2d1732a..eab27d41ba83 100644
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--- a/drivers/spi/spi-bcm2835.c
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+++ b/drivers/spi/spi-bcm2835.c
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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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--
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2.22.0
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