[meta-freescale] imx.c RXTL

[Frazer, Will]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.yoctoproject.org/pipermail/meta-freescale/attachments/20150429/e492a67e/attachment.html>