Date: Fri, 27 Apr 2001 22:00:04 -0700 (PDT) From: Rich Wales <richw@webcom.com> To: freebsd-bugs@FreeBSD.org Subject: Re: i386/26261: silo overflow problem in sio driver Message-ID: <200104280500.f3S504f85365@freefall.freebsd.org>
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The following reply was made to PR i386/26261; it has been noted by GNATS.
From: Rich Wales <richw@webcom.com>
To: freebsd-gnats-submit@freebsd.org
Cc:
Subject: Re: i386/26261: silo overflow problem in sio driver
Date: Fri, 27 Apr 2001 21:53:32 -0700 (PDT)
Earlier, I wrote:
> This presumably leaves open the question of whether the problem
> is due to a bug in XFree86-4.x itself, or if XFree86-4.x is
> innocently tickling some FreeBSD kernel bug.
The people on the "xpert@xfree86.org" list suggest that the XFree86-4
accelerator code is being overly aggressive about pipelining commands
to the video card -- and, in the process, is locking up the PCI bus
and interfering with the timely servicing of serial I/O interrupts.
I was able to sidestep the problem (and get rid of the silo overflows)
by enabling the "XaaNoScanlineCPUToScreenColorExpandFill" video driver
option (this disables "indirect" CPU-to-screen color expansion).
Alternatively, the "XaaNoSolidFillRect" option (disabling solid filled
rectangle acceleration) also fixed the problem. In either case, I see
no degradation of overall video performance.
The XFree86 people are still unclear as to how video acceleration ops
could lock up the PCI bus, so I suppose there might still be a bug
somewhere in FreeBSD that is allowing this problem to occur. So it
might not quite be time to close this PR yet.
Rich Wales richw@webcom.com http://www.webcom.com/richw/
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