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

Back before commit 1dccb598df54 ("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 c37f45b5f1cd ("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: c37f45b5f1cd ("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>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 656dd3e..f4d412e 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -805,12 +805,12 @@ static int __spi_map_msg(struct spi_master *master, struct spi_message *msg)
        if (master->dma_tx)
                tx_dev = master->dma_tx->device->dev;
        else
-               tx_dev = &master->dev;
+               tx_dev = master->dev.parent;
 
        if (master->dma_rx)
                rx_dev = master->dma_rx->device->dev;
        else
-               rx_dev = &master->dev;
+               rx_dev = master->dev.parent;
 
        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
                if (!master->can_dma(master, msg->spi, xfer))
@@ -852,12 +852,12 @@ static int __spi_unmap_msg(struct spi_master *master, struct spi_message *msg)
        if (master->dma_tx)
                tx_dev = master->dma_tx->device->dev;
        else
-               tx_dev = &master->dev;
+               tx_dev = master->dev.parent;
 
        if (master->dma_rx)
                rx_dev = master->dma_rx->device->dev;
        else
-               rx_dev = &master->dev;
+               rx_dev = master->dev.parent;
 
        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
                if (!master->can_dma(master, msg->spi, xfer))