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| author | Serge Semin <Sergey.Semin@baikalelectronics.ru> | 2020-05-29 16:11:57 +0300 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2020-05-29 15:55:48 +0100 |
| commit | 46164fde6b7890e7a3982d54549947c8394c0192 (patch) | |
| tree | d3f9932e5aab10bea964156fcd438d965a299f4c /drivers/spi | |
| parent | 0b2b66514fc9971b3a6002ba038d74f77705fd34 (diff) | |
| download | linux-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.c | 1 |
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; } } |