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    SubjectRe: Synaptics Touchpad workaround for strange behavior after Sync loss (With Patch).
    On Sat, Jan 10, 2004 at 11:50:02PM +0100, Peter Berg Larsen wrote:

    > On Fri, 9 Jan 2004, Vojtech Pavlik wrote:
    >
    > > The sync problems have so far been found to be caused by two possible
    > > causes:
    > >
    > > 1) Too long disabled interrupts. This is usually caused by ACPI
    > > BIOS, when some application is polling for battery status
    > > too often.
    > >
    > > 2) Incorrectly working timer (jiffies). This maybe caused by
    > > using the ACPI timer instead of the regular PIT one. Check
    > > the config.
    > >
    > > Both these causes break the lost bytes detection mechanism in the ps/2
    > > code. It then thinks that a byte was lost (and thus the sync, too), but
    > > in reality everything is OK. This in turn causes two consecutive
    > > incorrectly parsed packets.
    >
    > I also believe some of the troubles comes from that we never check all
    > error codes from the mux: If mux is disabled for some reason all bytes are
    > stamped as timed out. The only way to recover is to reboot. And (I am
    > speculating here) if for some reason the mux believe the touchpad is
    > removed and connected the touchpad sends 2 bytes ack.
    >
    > I dont have a machine with active multiplexing so the the patch is
    > untested. It warns when the mouse is removed, and tries to recover
    > if multiplexing is disabled.

    It's nice, but er definitely shouldn't call i8042_enable_mux() from the
    interrupt handler, because i8042_command() waits for characters arriving
    in the interrupt handler, so we could get into rather nasty recursions.

    --
    Vojtech Pavlik
    SuSE Labs, SuSE CR
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