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From: cgd@eden.CS.Berkeley.EDU (Chris G. Demetriou)
Newsgroups: comp.unix.bsd
Subject: Re: [386BSD] 16550 Not Resetting.
Date: 28 Nov 92 20:25:43
Organization: Kernel Hackers 'r' Us
Lines: 43
Message-ID: <CGD.92Nov28202543@eden.CS.Berkeley.EDU>
References: <By8FAD.KAo@ucunix.san.uc.edu> <CGD.92Nov26175845@toe.CS.Berkeley.EDU>
<1992Nov28.115716.8219@runx.oz.au>
NNTP-Posting-Host: eden.cs.berkeley.edu
In-reply-to: bde@runx.oz.au's message of 28 Nov 92 11:57:16 GMT
In article <1992Nov28.115716.8219@runx.oz.au> bde@runx.oz.au (Bruce Evans) writes:
>There is no way that the BIOS or a DOS driver can fully initialize an
>unsupported chip. Some of the bits to initialize a 16550 are in a register
>that doesn't need initializing for 8250-16450's. Control-Alt-Del doesn't
>reset the chip because the reset is soft.
<sigh> tell me, how long has the '550 been around?
>These bits are documented to be 0 for 8250-16450 chips.
generally, good designers consider bits with no function
but labeled as a certain value to be for identification only...
and they consider them "reserved"... (and they mask them off, when checking/
setting things...)
>Essentially this: for each port in 0x3f8, 0x2f8, ...
>
> outportb(port + 2, 4 | 2 | 1); /* reset FIFO (xmt | recv | enable) */
> outportb(port + 2, 0); /* turn FIFO off */
>
> The first step might be optional.
the first step is optional.
but remember, to do this correctly, EACH driver in the system needs a
"pre-reboot" entry point (or a placeholder which does nothing).
What i'm saying is, it's not feasible to add this support, when this is
the only instance thus far that i've seen that could use it, and this (only)
instance is the cause of faulty design.
the people who work on 386bsd can't be held accountable for the fact
that other software running on the same machine my not work correctly.
Chris
(a software-elitist...)
--
Chris G. Demetriou cgd@cs.berkeley.edu
"Sometimes it is better to have twenty million instructions by
Friday than twenty million instructions per second." -- Wes Clark