Hi All,

I've been looking at
http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/drivers/tty/serial/imx.c

& notice:

#define TXTL 2 /* reset default */
#define RXTL 1 /* reset default */

This seems to be setting the RX Threshold FIFO to 1 - rather than something 
more sensible like 14 which is more normal for 16550 compatible UARTS.

In tests I can see that with the value set as 1, under intensive serial use, 
CPU use goes towards about 20% (solo core). With the value set to 14 it's 
closer to 2%.

I can't think of a good reason why a FIFO would be set to interrupt for every 
character so is there some known bug/reason that anyone can advise me on as to 
why it is so?

Perhaps it's like this because it was only considered for console operation??

Thanks,
Will Frazer

Eurotech UK
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