Date: Wed, 24 Jul 2002 02:08:04 -0500 (CDT) From: John Utz <john@utzweb.net> To: "M. Warner Losh" <imp@bsdimp.com> Cc: tony@valemount.com, <mobile@FreeBSD.ORG>, <andrew@unfortu.net> Subject: Re: PCI -> PCMCIA Adapter woes - patch Message-ID: <Pine.LNX.4.44.0207240149440.23175-100000@jupiter.linuxengine.net> In-Reply-To: <20020723.150649.12657684.imp@bsdimp.com>
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Yah, i know there is newer mail on this thread, but the issue that i find to be most important is addressed quite well by MWL..... On Tue, 23 Jul 2002, M. Warner Losh wrote: > In message: <0f5001c23287$1a948530$114c35d1@tonyxp> > "Tony Toole" <tony@valemount.com> writes: > : Here is my patch to solve the problem you are having. It works very well, > : and you can use regular PCI IRQ routing with no /boot/loader.conf tweaks > : needed. NEWCARD also had the same problem, so this patch with subtle > : changes should fix it as well. > : > : I have included the patch as an attachment as email tends to mangle them. > > First off, the IRQMUX register is 12xx and newer. The documentation > for the MUX register indicates that it should be programmed once by > the eeprom that's on the board. Chances are that this is a workaround > for a bug in the card in question. > > However, a reasonable thing to do would likely be to do this if the > low nibble of the word was 0 (configuring it for a GPIO input, that > the code never uses), then set it up to do PCI signalling. > > I'm a little loathe to do this by default, because the docs say that > you have to have terminal resistors on these multifuction pins to use > them as outputs. I would be way loathe, IMHO. If you dont have the pullups ( the terminating resistors ) then you are basically gambling that card 'design slop' and chip fabrication process 'fudge factors' all work out in your favor. :-( The resistors 'hold the voltage up' and limit the current thru that portion of the circuit. If the chip has a lot of it's circuitry in parallel with that pin, which likely if it's multifunction, because that pin is designed to do more things than usual??. Next, if the card designer didnt keep the impedence of his portion of the design pretty high, then every time the chip tries to assert (set to logical high) that pin ( or, heaven help you, *several* of them at the same time ) then you will be mistreating that chip quite badly and it will at the very least 'act weird' and at the worst, fry. I dont think that the frying is likely, but 'act weird' is the one that i'd be betting on. And, if the card cost us$40.00, and you've spent the last N weeks of billable hours ( at a rate >=us$40.00/hr ) trying to figure out why the card 'spazzes out' periodically....wouldnt you have rathered that it had just cooked and died in the first few minutes and left a big cloud of smoke and an obviously discolored part on the PCB? :-) > However, given that this is the only way I know to drive the PCI bus, it > may make good sense to do it anyway. eek! i defer to your expertise. > Warner > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-mobile" in the body of the message > -- John L. Utz III john@utzweb.net Idiocy is the Impulse Function in the Convolution of Life To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-mobile" in the body of the message
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