Date: Sat, 21 Dec 1996 06:00:02 -0800 (PST) From: "Chad R. Larson" <chad@anasazi.com> To: freebsd-bugs Subject: Re: kern/2248: Mitsumi CD-ROM driver has Message-ID: <199612211400.GAA10502@freefall.freebsd.org>
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The following reply was made to PR kern/2248; it has been noted by GNATS.
From: "Chad R. Larson" <chad@anasazi.com>
To: freebsd-gnats-submit@freebsd.org, chad@anasazi.com
Cc: Subject: Re: kern/2248: Mitsumi CD-ROM driver has
Date: Sat, 21 Dec 1996 06:57:23 -0800
I turned on debugging for the driver. It reported that it was
finding data with a delay of between 10 and 40. I believe that
is the count of the number of times mcd_doread() scheduled itself
via timeout() before the controller reported status. If so, the
read delay value of 800 is more than enough. However, every dozen
or so reads do not ever get data. Those ones are the ones that
generate the timeout messages. The retrys always work. It is
almost as though the controller doesn't see the read data command
every so often.
I'm going to reduce the delay value from 800 to maybe 200. It won't
solve the read fails, but will get around to the retry much sooner
which should increase the effective throughput on the drive.
Other tidbits: Each completed read generates a "stray interrupt",
which tells me that the strategy of mcd_doread() repeatedly scheduling
itself wouldn't be necessary. Let the interrupt cause data to be
collected. Also, putting the computer into and out of "turbo" mode
(changing CPU clock rate from 133 MHz to 33MHz and back) doesn't seem
to impact the behavior, so I don't think it's directly related to
timing.
I suppose it's possible that the controller itself is defective, but
it was working perfectly in another machine.
Any other ideas to try?
-crl
--
Chad R. Larson (CRL22) Brother, can you paradigm?
602-953-1392 CRL22@aol.com chad@dcfinc.com chad@anasazi.com
DCF, Inc. - 14623 North 49th Place, Scottsdale, Az 85254-2207
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