From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 8A9C9B7187 for ; Mon, 21 Feb 2011 07:05:22 +1100 (EST) Subject: Re: Info : Using a PowerMac G5 as a server From: Benjamin Herrenschmidt To: Romain Goyet In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Mon, 21 Feb 2011 07:05:00 +1100 Message-ID: <1298232300.8833.20.camel@pasglop> Mime-Version: 1.0 Cc: Tony Breeds , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > Surprisingly, the Linux kernel does a very good job on this machine in > terms of hardware support and stability : everything works perfectly. > But the global OS fails pathetically in the two said points. > Here are my findings so far, I hope it will help people in the same situation : > > 1/ Booting a PowerMac G5 headless > > This hasn't so much to do with Linux per se, but rather with Yaboot > which seems to be the de-facto standard bootloader on the OpenFirmware > platform. > For some reason, at some point in the booting process, yaboot relies > on a screen being present. If no screen is attached, it will hang. So > much for headless booting. > Now I've figured out several workarounds : > -> Fake a screen by plugging in a resistor into your VGA port (or to > your DVI port using an adapter). This sure works, but it's rather > redneck > -> For some reason, the part of yaboot that actually depends on the > script is the "ofboot.b" forth script. This scripts' purpose is to > give you an option of booting off of a CD. I really don't get it since > OpenFirmware itself lets you boot off of a CD just by pressing "C" on > boot. So basically if you skip ofboot.b, you're good to go. When > installing yaboot with ybin, ybin sets the "boot-device" variable in > OpenFirmware to point to ofboot.b. So if you point boot-device > straight to the yaboo binary, you should be able to boot headless > without any issue. Here are several ways to do it : You may want to Tony Breeds. I'm not sure what happen when ofboot.b tries to "fixup" the input/output devices, but we could certainly make it easier for ofboot.b to be optional. > - Go to the OpenFirmware prompt (Command-Option-O-F on boot), > and type "setenv boot-device=hd:2,yaboot" (modify the hd:2 > accordingly), then "boot" > - You might be able to achieve the same effect using the > "nvram" tool straight from linux > - I think simply removing the "magicboot" line off of > yaboot.conf might fix it as well > > IOW, it _is_ possible to boot a PowerMac G5 headless on Linux without > any hardware modification. Yeah but I think OF gets into all kind of funny state if you try to open the graphics device with nothing connected, and that's an OF bug, it shouldn't happen. > 2/ Rebooting automagically after a power failure > > Now this is less fun : I still don't have any solution to offer. To > understand the situation, you should know that this has to be set in > the power-management chip. > Previous PowerMacs used a "PMU" chip, which was fully supported. All > you had to do was to echo "server_mode=1" to /proc/pmu/options. > > Thing is, G5's use a new chip, named "SMU". And AFAIK, there's no such > option for those machines… Yes, there is. We reverse engineered that a while back and somebody even wrote a little tool to control it, though I don't remember where that can be found... If necessary, we can try to dig again, the RE wasn't that hard. Cheers, Ben. > So if anyone ever knows any element of answer on this, I'd be really > interested ! > > Kind regards, > > - Romain > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev