spi: topcliff-pch: Prevent usage of potentially stale DMA device

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: 4d986ffa ("spi: add missing pci_dev_put() before return")
Reported-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220307173740.80996-1-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

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)