Messages in this thread |  | | From | bart@etpmod ... | Date | Fri, 27 Oct 2000 14:04:58 +0200 (CEST) | Subject | Re: Possible critical VIA vt82c686a chip bug (private question) |
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On 26 Oct, Vojtech Pavlik wrote: > On Thu, Oct 26, 2000 at 04:42:31PM +0200, Yoann Vandoorselaere wrote: > >> > On Thu, Oct 26, 2000 at 04:20:43PM +0200, Yoann Vandoorselaere wrote: >> > >> > > ... >> > > >> > > Have you any idea what is the relation between time and this chip ? >> > > >> > > Also, I'm experiencing the problem for several month on my >> > > workstation and I never could find where it was comming from... >> > > how did you do ? >> > >> > Well, it integrates both the i8253 PIT and the vt82c586 IDE controller. >> > >> > I first located the wrong time was coming from gettimeofday() and not >> > from the other sources of time the kernel provides. And then I was >> > tracking the problem (which actually is an underflow - the chip bug >> > causes some time offset variables go negative - 0xffffffff microseconds >> > is about 1:20 hours). And this way I got to the spot where the patch >> > cures the problem. >> >> Ok, here is what I experienced : >> >> First what is strange is that : >> - I'm using SCSI >> - I just have an IDE disk for mp3. >> The IDE subsystem is never used heavilly... >> >> I've experienced the problem after some time of >> heavy scsi IO, my screen under X was going black (like with dpms) >> When I was moving the mouse, the image was coming back >> for < 1 seconds, then black screen... >> >> The only fix was to kill X then to reboot. >> >> Anyway, thanks for your explaination... >> I'll do a feedback for this patch ASAP. > > Interesting. If it's caused by SCSI as well (might be), then it's not > caused by heavy IDE activity but rather than that it could be heavy > BusMastering activity instead (The IDE chip does BM as well). > > I'm still wondering if it could be a Linux kernel bug (bad/concurrent > accesses to the i8253 registers), this has to be checked. >
How sure are you that the chip is actually buggy? I ran into something similar a while ago, when I mixed the two arguments to an outb in a driver, and ended up writing MYPORT into the timer instead of 0x40 into MYPORT.
Bart -- Bart Hartgers - TUE Eindhoven Get my GPG key at http://etpmod.phys.tue.nl/bart/pubkey.gpg
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