Messages in this thread | | | Date | Tue, 01 Jan 2002 16:48:31 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH][RFC] AMD Elan patch |
| |
Christer Weinigel wrote:
> > Alternate Gate A20 Control Register (Port 00EEh) A special 8-bit > read/write control register provides a fast and reliable way to > control the CPU A20 signal. A dummy read of this register returns > a value of FFh and forces the CPU A20 to propagate to the core > logic, while a dummy write to this register will cause the CPU A20 > signal to be forced Low as long as no other A20 gate control > sources are forcing the CPU A20 signal to propagate. > > I think it's safe to assume that it takes effect immediately. >
What leads you to that conclusion? There is nothing in the above paragraph that would lead you to believe that.
> >>I'm also very uncomfortable with putting this where you do; I think it >>should be put before a20_kbc instead. If the BIOS is implemented >>correctly, it should be used. >> > > I disagree, the Elan SC410 is an embedded CPU, it's used in systems > that might not even have a BIOS (such as the Ericsson eBox that I've > been working with). Since there has to be a config option for this > CPU (the clock frequency selection) and a SC410-enabled kernel won't > work properly on a normal PC anyway, why not modify the boot sequence > so that it _always_ works on this CPU. >
If used sans BIOS you need *massive* modifications to the setup anyway, and you're talking a completely custom kernel. The reason to use the BIOS first is to give the platform vendor a hook to deal with platform-specific issues, and God knows there are plenty of those when it comes to A20. (The fact that the BIOSes on the boards we have discussed haven't provided such a hook is a bug in itself.)
-hpa
- 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/
| |