On Sat, 4 Feb 2012, Woodruff, Richard wrote:

When you have aggressive PM working at the SOC level you many times lost 
a character on UART every since OMAP2. A strange but true statement is 
it is nice to see it losing a character on mainline as it as in 
indication that PM is likely working.

We've been losing wakeup characters in mainline for many years now ;-)

One irritation was some internal interrupt sources were not linked to 
low power wakeup events. If you were in interrupt mode and got 
characters below watermark you could sleep before interrupt status 
showed up (as you had to wait several frame times before functional 
interrupt asserted) but there was no wake at anticipated frame timeout 
because lack of linking of internal event to wake event.

Indeed, it seems that we are just now working around these wakeup-related 
bugs.  Kind of surprising that no errata showed up for them.

What's particularly remarkable is that it looks like the UARTs will 
idle-ack while their transmit FIFOs have data in them (!)


- Paul