Date: Fri, 12 Jul 1996 08:54:57 +1000 From: Bruce Evans <bde@zeta.org.au> To: alex@fa.tdktca.com, graichen@axp5.physik.fu-berlin.de Cc: hackers@FreeBSD.org Subject: Re: sio / modem problems Message-ID: <199607112254.IAA18667@godzilla.zeta.org.au>
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>> i have an internal creatix phone-master modem - which will be detected in >> FreeBSD 2.0.5 but not in the 2.1.0 RELEASE or the march 2.2 snap - it's The probe didn't change (not even one byte of the source) between 2.0.5R and 2.1.0R. Revision 1.135 on 25 Feb introduced some delays in the probe in the hope of fixing this problem. These should be in the March 2.2 snap. These changes are missing from -stable :-(. (Or `:-)' if they actually make things worse :-). The probe hasn't changed significantly in -current since rev.1.135. >I recently fixed a modem detection problem from someone by inserting >"DELAY(1000);"'s in sioprobe() everywhere the /* EXTRA DELAY? */ comment >appeared. It's a hack, but clearly some portion of that code is running The delays in rev.1.135 are in slightly different places. They are probably necessary if the UART is actually a bunch of i/o ports under software control. The software can reasonably take a long time to complete a sequence of events that it initiates. OTOH, for events initiated by the host cpu, such as writes to control registers, the UART needs to respond withing a few hundred nsec to preserve 16550 compatibility. Otherwise back to back writes to a control register might lose the intermediate steps... I added delays in exactly the cases where it seems reasonable for the UART to be slow. Bruce
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