Messages in this thread | | | Date | Sat, 29 Jan 2005 12:02:13 -0800 | From | "Randy.Dunlap" <> | Subject | Re: i8042 access timings |
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Vojtech Pavlik wrote: > On Fri, Jan 28, 2005 at 04:20:58PM +0200, Jaco Kroon wrote: > >>Vojtech Pavlik wrote: >> >>>On Thu, Jan 27, 2005 at 09:29:47PM +0100, Andries Brouwer wrote: >>> >>> >>> >>>>>So what _might_ happen is that we write the command, and then >>>>>i8042_wait_write() thinks that there is space to write the data >>>>>immediately, and writes the data, but now the data got lost because the >>>>>buffer was busy. >>>> >>>>Hmm - I just answered the same post and concluded that I didnt understand, >>>>so you have progressed further. I considered the same possibility, >>>>but the data was not lost since we read it again later. >>>>Only the ready flag was lost. >>> >>> >>>What I believe is happening is that we're talking to SMM emulation of >>>the i8042, which doesn't have a clue about these commands, while the >>>underlying real hardware implementation does. And because of that they >>>disagree on what should happen when the command is issued, and since the >>>SMM emulation lazily synchronizes with the real HW, we only get the data >>>back with the next command. >>> >>>I still don't have an explanation why both 'usb-handoff' and 'acpi=off' >>>help, I'd expect only the first to, but it might be related to the SCI >>>interrupt routing which isn't done when 'acpi=off'. Just a wild guess. >>> >> >>Ok, I'm not too clued up with recent hardware and the BIOS programming >>that goes with it (being a system admin/application programmer), what >>exactly is usb-handoff? > > > usb-handoff is a kernel option that enables a PCI quirk routine that > takes the USB controller out of BIOS's hands. Until that is done (the > linux USB drivers also do it, only later), the BIOS owns the USB > controller and tries to emulate a PS/2 mouse and keyboard for systems > which can't handle USB. > > >> acpi=off obviously just turns all acpi support >>in the kernel off. > > > Indeed. > > >>SCI is also a new abbreviation I haven't seen >>before. > > > System Configuration Interrupt. In addition to SMI (System Management > Interrupt), these are two interrupts the BIOS uses to do its job behind > the operating system's back.
ACPI 2.0 spec says: System Control Interrupt (SCI) A system interrupt used by hardware to notify the OS of ACPI events. The SCI is an active, low, shareable, level interrupt.
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