Messages in this thread | | | Date | Tue, 03 Sep 2013 10:35:04 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] reboot: perform warm/cold reset correctly for CF9 type |
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On 08/21/2013 08:32 PM, Li, Fei wrote: > > In fact, ACPI method also implements reset by writing RESET_VALUE into RESET_REG > port. In our platform, it also uses port 0xCF9. The difference between cold and wart reset > is whether power cycle is involved or not. After all, this is another topic. > > From the source code, CF9 boot method are still used by some apple MAC and dell > platforms if I understand correctly. > > Back to our patch, if you really concern the effect of cold reboot 0x0E to current existed > platforms, we can set the default value of reboot_mode as REBOOT_WARM. > > Does it make sense? >
Sort-of-kind-of.
The problem here is that "cold" versus "warm" reboot seems to have slightly different meanings for BIOS (bypass POST) and the CF9 register (where I presume it is a "deeper" platform reset of some kind ... is it even well-defined what the semantics are?)
I could be wrong and the cold/warm reset values in CF9 end up having exactly the same function as the magic BIOS signature does; if so, then I would like to be told so explicitly, ideally with an explanation about how it works on the hw level (or a pointer to relevant documentation, Intel internal docs are fine.)
Finally, again, does this solve a real problem?
-hpa
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