spi: When no dma_chan map buffers with spi_master's parent

Browse source

commit 88b0aa544a upstream.

Back before commit 1dccb598df ("arm64: simplify dma_get_ops"), for
arm64, devices for which dma_ops were not explicitly set were automatically
configured to use swiotlb_dma_ops, since this was hard-coded as the
global "dma_ops" in arm64_dma_init().

Now that global "dma_ops" has been removed, all devices much have their
dma_ops explicitly set by a call to arch_setup_dma_ops(), otherwise the
device is assigned dummy_dma_ops, and thus calls to map_sg for such a
device will fail (return 0).

Mediatek SPI uses DMA but does not use a dma channel.  Support for this
was added by commit c37f45b5f1 ("spi: support spi without dma channel
to use can_dma()"), which uses the master_spi dev to DMA map buffers.

The master_spi device is not a platform device, rather it is created
in spi_alloc_device(), and therefore its dma_ops are never set.

Therefore, when the mediatek SPI driver when it does DMA (for large SPI
transactions > 32 bytes), SPI will use spi_map_buf()->dma_map_sg() to
map the buffer for use in DMA.  But dma_map_sg()->dma_map_sg_attrs() returns
0, because ops->map_sg is dummy_dma_ops->__dummy_map_sg, and hence
spi_map_buf() returns -ENOMEM (-12).

Fix this by using the real spi_master's parent device which should be a
real physical device with DMA properties.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Fixes: c37f45b5f1 ("spi: support spi without dma channel to use can_dma()")
Cc: Leilk Liu <leilk.liu@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Daniel Kurtz 2017-01-27 00:21:53 +08:00 • committed by Greg Kroah-Hartman

parent 478273e115

commit c52829f60f

1 changed files with 4 additions and 4 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

8

drivers/spi/spi.c

View file