Date: Tue, 11 May 2004 00:19:21 -0700 (PDT) From: Bruce Evans <bde@FreeBSD.org> To: Thorsten.Kuehnemann@Hamburg.de, bde@FreeBSD.org, freebsd-i386@FreeBSD.org Subject: Re: i386/55930: partly configured serial port freezes system Message-ID: <200405110719.i4B7JLWF097908@freefall.freebsd.org>
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Synopsis: partly configured serial port freezes system State-Changed-From-To: open->analyzed State-Changed-By: bde State-Changed-When: Mon May 10 23:52:00 PDT 2004 State-Changed-Why: This is most likely caused by setting the device flag 0x10 on the unconfigured sio0 port. The device flag 0x10 is more than a hint; it forces the last sio port with this bit set to be the preferred serial console (if there is a serial console), and the probe is forced to succeed for the preferred serial console (whether or not this is the actual console). If the preferred serial console is the actual console, then the system tends to hang printing the first boot message to it. Otherwise the system tends to hang later if the port is accessed from userland. Unfortunately, setting the device flag 0x10 on sio0 is the default. The problem is rarely seen because an sio0 port at address 0x3F8 used to be standard hardware, so it took unconfiguring this port to cause the problem. This problem is indicated by the "type 8250 or not responding" message. The "configured irq N not in bitmap" message is normal for ports that are detected to be not there. This message should not be printed if the probe fails (except when booting with -v so that the reasons for the failure are printed). Related problem: the preferred serial console is documented to be the first port (in config file order) with 0x10 set in its flags, but it actually the last such port (in unit number order). See also PR 33963. http://www.freebsd.org/cgi/query-pr.cgi?pr=55930
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