tty: serial: pch: don't crash if DMA enabled but not loaded
if the DMA driver isn't loaded "on time" then we crash in the irq handler:
| pch_uart 0000:02:0a.4: pch_request_dma:dma_request_channel FAILS(Tx)
| BUG: unable to handle kernel NULL pointer dereference at (null)
| IP: [<c0676ed9>] pch_uart_interrupt+0x739/0x940
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index 0aa2b52..6bb7e90 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -1508,10 +1508,14 @@
__func__);
return -EOPNOTSUPP;
#endif
- dev_info(priv->port.dev, "PCH UART : Use DMA Mode\n");
- if (!priv->use_dma)
+ if (!priv->use_dma) {
pch_request_dma(port);
- priv->use_dma = 1;
+ if (priv->chan_rx)
+ priv->use_dma = 1;
+ }
+ dev_info(priv->port.dev, "PCH UART: %s\n",
+ priv->use_dma ?
+ "Use DMA Mode" : "No DMA");
}
return 0;