Messages in this thread | | | From | brian@worldcon ... | Date | Sat, 20 Nov 1999 01:43:50 -0800 | Subject | Re: [gphoto-kodak] Re: Kodak DC-265 overrunning linux serial driver? |
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On Fri, Nov 19, 1999 at 06:44:57PM -0500, Theodore Y. Ts'o wrote: > The problem is that certain other device drivers (and the IDE PIO driver > is the prime example) keeps interrupts off to long, thus increasing the > interrupt latency to the point where you start overflowing the FIFO. > Increasing the buffer which the interrupt routine uses to copy > characters out of the FIFO isn't going to help, because they're getting > lost before the interrupt routine even has a chance to run.
I did some testing on my laptop with linux 2.2.13.
So far as I can tell my HD on the laptop is running in DMA mode. Additionally, the 'hdparm -u 1 /dev/hda' had no effect on the overrun problem.
It acted pretty much as Jim has described. With the FIFO level mod, Nearly 100% failure at 115200, 10% failure at 57600.
At 115200 it always fails, so far as I can tell, right away. Long before any data is actually written to disk.
One of the "other" drivers must be holding of the serial interrupt for too long.
-- Brian Litzinger <brian@litzinger.com>
Copyright (c) 1999 By Brian Litzinger, All Rights Reserved
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