[PATCH] tty: serial: 8250: omap: fix kernel crash in suspend-to-ram

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omap_device infrastructure has a suspend_noirq hook which
runtime suspends all devices late in the suspend cycle (see
_od_suspend_noirq() in arch/arm/mach-omap2/omap_device.c)

This leads to a NULL pointer exception in 8250_omap driver
since by the time omap8250_runtime_suspend() is called, 8250_dma
driver has already set rxchan to NULL via serial8250_release_dma().

Make an explicit check to see if rxchan is NULL in
runtime_{suspend|resume} hooks to fix this.

Signed-off-by: Sekhar Nori <nsekhar@xxxxxx>
---
This applies to latest linus/master. I can rebase and
resend after -rc1 is tagged if needed.

 drivers/tty/serial/8250/8250_omap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index dce1a23706e8..2331dd0bbe5f 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -1301,7 +1301,7 @@ static int omap8250_runtime_suspend(struct device *dev)
 	}
 
 	omap8250_enable_wakeup(priv, true);
-	if (up->dma)
+	if (up->dma && up->dma->rxchan)
 		omap_8250_rx_dma(up, UART_IIR_RX_TIMEOUT);
 
 	priv->latency = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE;
@@ -1327,7 +1327,7 @@ static int omap8250_runtime_resume(struct device *dev)
 	if (loss_cntx)
 		omap8250_restore_regs(up);
 
-	if (up->dma)
+	if (up->dma && up->dma->rxchan)
 		omap_8250_rx_dma(up, 0);
 
 	priv->latency = priv->calc_latency;
-- 
2.4.4.408.g16da57c

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