[PATCH v1 1/1] spi: topcliff-pch: Prevent usage of potentially stale DMA device

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

DMA device is expected to be available while SPI transfer is ongoing.

Prevent usage of potentially stale DMA device by keeping reference
count till the end of the transfer.

Fixes: 4d986ffa036a ("spi: add missing pci_dev_put() before return")
Reported-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
 drivers/spi/spi-topcliff-pch.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-topcliff-pch.c b/drivers/spi/spi-topcliff-pch.c
index 8e1cc345810a..dfaa1d79a78b 100644
--- a/drivers/spi/spi-topcliff-pch.c
+++ b/drivers/spi/spi-topcliff-pch.c
@@ -103,6 +103,7 @@
 static int use_dma = 1;
 
 struct pch_spi_dma_ctrl {
+	struct pci_dev		*dma_dev;
 	struct dma_async_tx_descriptor	*desc_tx;
 	struct dma_async_tx_descriptor	*desc_rx;
 	struct pch_dma_slave		param_tx;
@@ -876,7 +877,6 @@ static void pch_spi_request_dma(struct pch_spi_data *data, int bpw)
 	if (!chan) {
 		dev_err(&data->master->dev,
 			"ERROR: dma_request_channel FAILS(Tx)\n");
-		data->use_dma = 0;
 		goto out;
 	}
 	dma->chan_tx = chan;
@@ -893,13 +893,15 @@ static void pch_spi_request_dma(struct pch_spi_data *data, int bpw)
 			"ERROR: dma_request_channel FAILS(Rx)\n");
 		dma_release_channel(dma->chan_tx);
 		dma->chan_tx = NULL;
-		data->use_dma = 0;
 		goto out;
 	}
 	dma->chan_rx = chan;
 
+	dma->dma_dev = dma_dev;
+	return;
 out:
 	pci_dev_put(dma_dev);
+	data->use_dma = 0;
 }
 
 static void pch_spi_release_dma(struct pch_spi_data *data)
@@ -915,6 +917,8 @@ static void pch_spi_release_dma(struct pch_spi_data *data)
 		dma_release_channel(dma->chan_rx);
 		dma->chan_rx = NULL;
 	}
+
+	pci_dev_put(dma->dma_dev);
 }
 
 static void pch_spi_handle_dma(struct pch_spi_data *data, int *bpw)
-- 
2.34.1