pch_uart: Fix dma channel unallocated issue

commit af6d17cdc8c89aeb3101f0d27cd32fc0592b40b2 upstream.

This driver anticipates pch_uart_verify_port() is not called
during installation.
However, actually pch_uart_verify_port() is called during
installation.
As a result, memory access violation occurs like below.

0. initial value: use_dma=0
1. starup()
    - dma channel is not allocated because use_dma=0
2. pch_uart_verify_port()
    - Set use_dma=1
3. UART processing acts DMA mode because use_dma=1
     - memory access violation occurs!

This patch fixes the issue.

Solution:
Whenever pch_uart_verify_port() is called and then
dma channel is not allocated, the channel should be allocated.

Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index da776a0..a4b192d 100644 (file)
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -1356,9 +1356,11 @@ static int pch_uart_verify_port(struct uart_port *port,
                        __func__);
                return -EOPNOTSUPP;
 #endif
                        __func__);
                return -EOPNOTSUPP;
 #endif

-               priv->use_dma = 1;

                priv->use_dma_flag = 1;
                dev_info(priv->port.dev, "PCH UART : Use DMA Mode\n");
                priv->use_dma_flag = 1;
                dev_info(priv->port.dev, "PCH UART : Use DMA Mode\n");

+               if (!priv->use_dma)
+                       pch_request_dma(port);
+               priv->use_dma = 1;

        }
 
        return 0;
        }
 
        return 0;