[PATCH v2] 8250_lpss: check null return when calling pci_ioremap_bar

[Navid Emamdoost]

pci_ioremap_bar may return null. This is eventually de-referenced at 
drivers/dma/dw/core.c:1154 and drivers/dma/dw/core.c:1168. A null check 
is needed to prevent null de-reference. I am adding the check and in case
 of failure. Thanks to Andy Shevchenko for the hint on the necessity of 
pci_iounmap when exiting.

Signed-off-by: Navid Emamdoost <navid.emamdo...@gmail.com>
---
 drivers/tty/serial/8250/8250_lpss.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_lpss.c 
b/drivers/tty/serial/8250/8250_lpss.c
index 53ca9ba6ab4b..d07e431110d9 100644
--- a/drivers/tty/serial/8250/8250_lpss.c
+++ b/drivers/tty/serial/8250/8250_lpss.c
@@ -169,10 +169,12 @@ static void qrk_serial_setup_dma(struct lpss8250 *lpss, 
struct uart_port *port)
        struct pci_dev *pdev = to_pci_dev(port->dev);
        int ret;
 
+       chip->pdata = &qrk_serial_dma_pdata;
        chip->dev = &pdev->dev;
        chip->irq = pci_irq_vector(pdev, 0);
        chip->regs = pci_ioremap_bar(pdev, 1);
-       chip->pdata = &qrk_serial_dma_pdata;
+       if (!chip->regs)
+               return;
 
        /* Falling back to PIO mode if DMA probing fails */
        ret = dw_dma_probe(chip);
@@ -195,11 +197,15 @@ static void qrk_serial_setup_dma(struct lpss8250 *lpss, 
struct uart_port *port)
 
 static void qrk_serial_exit_dma(struct lpss8250 *lpss)
 {
+       struct dw_dma_chip *chip = &lpss->dma_chip;
        struct dw_dma_slave *param = &lpss->dma_param;
 
        if (!param->dma_dev)
                return;
-       dw_dma_remove(&lpss->dma_chip);
+
+       dw_dma_remove(chip);
+
+       pci_iounmap(to_pci_dev(chip->dev), chip->regs);
 }
 #else  /* CONFIG_SERIAL_8250_DMA */
 static void qrk_serial_setup_dma(struct lpss8250 *lpss, struct uart_port 
*port) {}
-- 
2.17.1