* Sebastian Andrzej Siewior [off-list ref] [140815 12:16]:

On 08/15/2014 08:17 PM, Lennart Sorensen wrote:

quoted

Are you saying that with the new driver you have to respond to the RX
irq faster than before to avoid overflows?  It is not quite clear.

Yes. The irq fires 46 bytes giving you 16 bytes buffer before overflow
vs 63 bytes buffer the old one had.

quoted

I do think 40000 interrupts to handle 40000 bytes of date does seem a
tad inefficient, so dropping to 854 looks a lot nicer.  Was the omap
driver not using the fifo trigger levels at all?

It configured the trigger levels to 1 for RX and 16 for TX.

Hmm that weird RX trigger level is a workaround for lost characters.

See commit 0ba5f66836 (tty: serial: OMAP: use a 1-byte RX FIFO
threshold in PIO mode :)

There's paste test in that commit, I wonder if the 8250 drivers
can deal with it any better?

Regards,

Tony