tty: serial: fsl_lpuart: fix DMA operation when using IOMMU

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The DMA channel might not be available at probe time. This is esp. the
case if the DMA controller has an IOMMU mapping.

There is also another caveat. If there is no DMA controller at all,
dma_request_chan() will also return -EPROBE_DEFER. Thus we cannot test
for -EPROBE_DEFER in probe(). Otherwise the lpuart driver will fail to
probe if, for example, the DMA driver is not enabled in the kernel
configuration.

To workaround this, we request the DMA channel in _startup(). Other
serial drivers do it the same way.

Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20200306214433.23215-2-michael@walle.cc
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Michael Walle 2020-03-06 22:44:30 +01:00 • committed by Greg Kroah-Hartman

parent d3394b3d51

commit 159381df14

1 changed files with 57 additions and 31 deletions

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drivers/tty/serial/fsl_lpuart.c

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