[RFC PATCH 2/2] serial: 8250_dw: support polling mode

[John Garry <john.garry@huawei.com>]

It would be useful to make this driver support some
8250-compatible devices which have no interrupt line.

For these, we allow for no interrupt, and will fallback on
polling mode.

Note: the 8250 dt bindings state that "interrupts"
is a required property:
"interrupts : should contain uart interrupt."

But the 8250_of.c driver can live without it. So
this patch is going this way also.

Signed-off-by: John Garry <john.garry@huawei.com>
---
 drivers/tty/serial/8250/8250_dw.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 28fbc8f..3154988 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -422,9 +422,10 @@ static int dw8250_probe(struct platform_device *pdev)
 	}
 
 	if (irq < 0) {
-		if (irq != -EPROBE_DEFER)
-			dev_err(dev, "cannot get irq\n");
-		return irq;
+		if (irq == -EPROBE_DEFER)
+			return irq;
+		dev_warn(dev, "cannot get irq, using polling mode\n");
+		irq = 0;
 	}
 
 	spin_lock_init(&p->lock);
-- 
1.9.1