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authorSerge Semin <Sergey.Semin@baikalelectronics.ru>2020-05-29 16:11:57 +0300
committerMark Brown <broonie@kernel.org>2020-05-29 15:55:48 +0100
commit46164fde6b7890e7a3982d54549947c8394c0192 (patch)
treed3f9932e5aab10bea964156fcd438d965a299f4c /drivers/spi
parent0b2b66514fc9971b3a6002ba038d74f77705fd34 (diff)
downloadlinux-46164fde6b7890e7a3982d54549947c8394c0192.tar.bz2
spi: dw: Fix Rx-only DMA transfers
Tx-only DMA transfers are working perfectly fine since in this case the code just ignores the Rx FIFO overflow interrupts. But it turns out the SPI Rx-only transfers are broken since nothing pushing any data to the shift registers, so the Rx FIFO is left empty and the SPI core subsystems just returns a timeout error. Since DW DMAC driver doesn't support something like cyclic write operations of a single byte to a device register, the only way to support the Rx-only SPI transfers is to fake it by using a dummy Tx-buffer. This is what we intend to fix in this commit by setting the SPI_CONTROLLER_MUST_TX flag for DMA-capable platform. Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru> Cc: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Feng Tang <feng.tang@intel.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: linux-mips@vger.kernel.org Cc: devicetree@vger.kernel.org Link: https://lore.kernel.org/r/20200529131205.31838-9-Sergey.Semin@baikalelectronics.ru Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/spi-dw.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index 73af58dbcd6a..1f1a3536b7cf 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -515,6 +515,7 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
dev_warn(dev, "DMA init failed\n");
} else {
master->can_dma = dws->dma_ops->can_dma;
+ master->flags |= SPI_CONTROLLER_MUST_TX;
}
}