Messages in this thread |  | | From | "H. Peter Anvin" <> | Subject | Re: setup.S: A20 enable sequence (once again) | Date | 6 Nov 2000 12:16:29 -0800 |
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Followup to: <00110620483000.11673@rob> By author: Robert Kaiser <rob@sysgo.de> In newsgroup: linux.dev.kernel > > > This doesn't really work. Neither the fast A20 gate nor the KBC is > > guaranteed to have immediate effect (on most systems they won't.) > > In that case, maybe I should do repeated calls to a20_check with a > (not too big) retry count after the port 92 write ? > > Problem is, it happens to work this way on all hardware I have access to, > so I can't really reproduce such timing problems. Anyone ? > > > What's worse, once you have done an "out" to the KBC you need to > > finish the sequence. I need to think about this for a bit. > > ??? I'm not touching the KBC if the port 92 access was successful at > enableing A20. If, however, A20 is still disabled, I'm doing the same KBC > sequence as the original code, so there shouldn't be any incomplete KBC > interactions (unless I mistyped something...). >
The problem is that your test for A20 is faulty. Severely so. Anyway, I just sent you a patch which will terminate the first empty_8042 loop (while it's still safe) if it finds A20 now enabled.
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