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tty: serial: pch: don't crash if DMA enabled but not loaded

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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>
This commit is contained in:
Sebastian Andrzej Siewior 2013-12-04 20:52:49 +01:00 committed by Greg Kroah-Hartman
parent 0da3336f19
commit e41c098121
1 changed files with 7 additions and 3 deletions
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10
drivers/tty/serial/pch_uart.c
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@ -1508,10 +1508,14 @@ static int pch_uart_verify_port(struct uart_port *port,
__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;