serial: 8250_mid: Balance reference count for PCI DMA device

[ Upstream commit 67ec6dd ]

The pci_get_slot() increases its reference count, the caller
must decrement the reference count by calling pci_dev_put().

Fixes: 90b9aac ("serial: 8250_pci: add Intel Tangier support")
Fixes: f549e94 ("serial: 8250_pci: add Intel Penwell ports")
Reported-by: Qing Wang <wangqing@vivo.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Depends-on: d9eda9b ("serial: 8250_pci: Intel MID UART support to its own driver")
Link: https://lore.kernel.org/r/20220215100920.41984-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/tty/serial/8250/8250_mid.c

@@ -73,6 +73,11 @@ static int pnw_setup(struct mid8250 *mid, struct uart_port *p)
 	return 0;
 }
 
+static void pnw_exit(struct mid8250 *mid)
+{
+	pci_dev_put(mid->dma_dev);
+}
+
 static int tng_handle_irq(struct uart_port *p)
 {
 	struct mid8250 *mid = p->private_data;
@@ -124,6 +129,11 @@ static int tng_setup(struct mid8250 *mid, struct uart_port *p)
 	return 0;
 }
 
+static void tng_exit(struct mid8250 *mid)
+{
+	pci_dev_put(mid->dma_dev);
+}
+
 static int dnv_handle_irq(struct uart_port *p)
 {
 	struct mid8250 *mid = p->private_data;
@@ -330,9 +340,9 @@ static int mid8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 
 	pci_set_drvdata(pdev, mid);
 	return 0;
+
 err:
-	if (mid->board->exit)
-		mid->board->exit(mid);
+	mid->board->exit(mid);
 	return ret;
 }
 
@@ -342,22 +352,23 @@ static void mid8250_remove(struct pci_dev *pdev)
 
 	serial8250_unregister_port(mid->line);
 
-	if (mid->board->exit)
-		mid->board->exit(mid);
+	mid->board->exit(mid);
 }
 
 static const struct mid8250_board pnw_board = {
 	.flags = FL_BASE0,
 	.freq = 50000000,
 	.base_baud = 115200,
 	.setup = pnw_setup,
+	.exit = pnw_exit,
 };
 
 static const struct mid8250_board tng_board = {
 	.flags = FL_BASE0,
 	.freq = 38400000,
 	.base_baud = 1843200,
 	.setup = tng_setup,
+	.exit = tng_exit,
 };
 
 static const struct mid8250_board dnv_board = {