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 31A2B1007D2 for ; Mon, 11 Jan 2010 14:04:32 +1100 (EST) Subject: Re: [PATCH] Re: ZILOG serial port broken in 2.6.32 From: Benjamin Herrenschmidt To: Rob Landley In-Reply-To: <201001090217.25729.rob@landley.net> References: <200912060101.22515.rob@landley.net> <200912080642.52103.rob@landley.net> <1262919644.2173.704.camel@pasglop> <201001090217.25729.rob@landley.net> Content-Type: text/plain; charset="UTF-8" Date: Mon, 11 Jan 2010 14:02:16 +1100 Message-ID: <1263178936.724.91.camel@pasglop> Mime-Version: 1.0 Cc: paulus@samba.org, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, 2010-01-09 at 02:17 -0600, Rob Landley wrote: > On Thursday 07 January 2010 21:00:43 Benjamin Herrenschmidt wrote: > > > Ok, here's the fix. It's not the _right_ fix, but it Works For Me (tm) > > > and I'll leave it to you guys to figure out what this _means_: > > > > I've failed to reproduce so far on both a Wallstreet powerbook (similar > > generation and chipset as your beige G3) and a G5 with an added serial > > port using current upstream... > > > > Can you verify it's still there ? I might be able to reproduce on a > > Beige G3 as well next week. > > It's still there on qemu 0.11.0's "g3beige" emulation when you use > CONFIG_SERIAL_PMACZILOG as the serial console. (QEMU 0.10.x used a 16550 > serial chip for its g3beige emulation instead of the actual ZILOG one.) Still > dunno if it's a qemu or bug or a kernel bug, I just know that kernel patch > fixes it for me, and it comes back without the patch. > > I tested 2.6.32. Haven't tried the 2.6.32.3 but don't see why it would change > this... Ok so I compiled qemu and things are a bit strange. How do you get the output of both channels of the serial port with it ? If I use -nographics, what happens is that OpenBIOS, for some reason, tells qemu that the console on the second channel of the ESCC. I see my kernel messages in the console if I do console=ttyPZ0 but the debug stuff goes where udbg initializes it, which is where OpenBIOS says the FW console is, which is channel B and I don't know how to "see" that with qemu. I do see it crash due to a message from the kernel but I can't get into xmon which is a pain. If I modify the kernel to force udbg on channel A (same channel as the console), then the problem doesn't appear (it doesn't crash) :-) Cheers Ben.