I have a question/problem with the serial driver.
This is with a 2.0.30 kernel, but a quick look at 2.2.5 tells
me that this version would most likely exhibit the same problem.
The problem I'm seeing is that the serial driver takes too long to
handle a receive interrupt because it runs while interrupts are disabled.
As a result, other, higher-prioritized interrupts cannot be handled in time.
This has bad effects on the systems in that it causes my sound driver
to not refill its codec's fifo in run, which in turn results in underruns
and interruptions of the audio play.
My questions:
+ why does the serial driver run with interrupts disabled for so long?
+ has anybody seen that problem?
+ how could one fix it?
Here's what I tried. I added a pair of sti(); cli(); in the
receive_chars() do { } while() loop right before the serial_inp().
Like so:
receive_chars()
{
do {
sti();
cli();
... serial_inp()
...
} while ( ... )
}
This appears to more or less work for a single serial port, but is it safe
(methinks it's not, especially if there's more than one serial port on the
machine.) That's on a 200MHz StrongARM, btw.
Thanks,
- Godmar
ps: it would be nice to cc me if someone replied to this.
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