Messages in this thread | | | Date | Fri, 13 Aug 2004 12:13:30 +0200 | From | "David N. Welton" <> | Subject | Re: 2.6 kernel won't reboot on AMD system - 8042 problem? |
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Vojtech Pavlik wrote:
> All in all, 0x65 is what one would expect to be in the CTR register > after boot on a normal machine without a PS/2 mouse installed.
Sure, if you search google on the results from the 20 command, you see a lot of things like 0x64 0x64 0x75 0x74 and similar values.
> 0x9a doesn't make sense _AT_ALL_, though!
Right.
> And there comes a thought ... > > In i8042_command(), we do this: > > if (!retval) > for (i = 0; i < ((command >> 8) & 0xf); i++) { > if ((retval = i8042_wait_read())) break; > if (i8042_read_status() & I8042_STR_AUXDATA) > param[i] = ~i8042_read_data(); > else > param[i] = i8042_read_data(); > dbg("%02x <- i8042 (return)", param[i]); > } > > to distinguish whether a response came from the AUX interface instead of > the KBD or controller itself. We _negate_ the value if the AUXDATA bit is > set in he status register.
Oh, yep, there we go... that's what's switching it around.
> So I think what happens is that the controller sets the AUXDATA bit for > some reason (or at least we read a status byte with the AUXDATA bit > set), which negates the value when we read the initial CTR.
> Then when we write that nonsensical CTR back to the controller on > reboot, we're screwed, since the i8042 is the more important CPU in the > system and can do many nasty things to it. ;)
> Now, the question is, where does that AUXDATA bit come from?
I noticed that the FreeBSD folks attempt to flush both kbd and aux:
http://fxr.watson.org/fxr/source/dev/kbd/atkbdc.c#L790
I tried doing that like so:
while ((i8042_read_status() & (I8042_STR_OBF | I8042_STR_AUXDATA)) && (i++ < I8042_BUFFER_SIZE)) { data = i8042_read_data(); dbg("%02x <- i8042 (flush, %s)", data, i8042_read_status() & I8042_STR_AUXDATA ? "aux" : "kbd"); }
with different variations, and it seems as if it will go on reading forever if you let it. So it keeps reporting AUXDATA as being present... Hrm...
-- David N. Welton davidw@eidetix.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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