[PATCH] serial imx.c: fix CTS trigger level lower to avoid lost chars

[Russell King - ARM Linux]

On Fri, Jan 22, 2010 at 04:47:13PM +0000, Jamie Lokier wrote:
> Any tips on how to make the serial receive irq latency more reliable
> on ARM, with a boringly generic serial driver?

What you could do is arrange for a backtrace to be printed when
you read an overrun condition from the UART - if interrupts were
disabled by something taking a long time, and then enabled, you
should see the point where they were just enabled in the backtrace.

It could be down to another IRQF_DISABLED interrupt - in which case
you won't see it in the backtrace.

Of course, printing a backtrace will cause subsequent overruns...