linux-kernel - [PATCH 4.9 143/172] spi: When no dma_chan map buffers with spi

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Message-Id: <20170703133421.022797209@linuxfoundation.org>
Date:   Mon,  3 Jul 2017 15:35:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Daniel Kurtz <djkurtz@...omium.org>,
        Leilk Liu <leilk.liu@...iatek.com>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH 4.9 143/172] spi: When no dma_chan map buffers with spi_masters parent

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Kurtz <djkurtz@...omium.org>

commit 88b0aa544af58ce3be125a1845a227264ec9ab89 upstream.

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@...omium.org>
Fixes: c37f45b5f1cd ("spi: support spi without dma channel to use can_dma()")
Cc: Leilk Liu <leilk.liu@...iatek.com>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/spi/spi.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -797,12 +797,12 @@ static int __spi_map_msg(struct spi_mast
 	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))
@@ -844,12 +844,12 @@ static int __spi_unmap_msg(struct spi_ma
 	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))