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 9650DDDDF8 for ; Tue, 18 Nov 2008 07:13:08 +1100 (EST) Subject: Re: pmac_zilog debugging ... From: Benjamin Herrenschmidt To: Kevin Diggs In-Reply-To: <492145BB.7080904@hypersurf.com> References: <4914B549.9010805@hypersurf.com> <1226096603.13603.74.camel@pasglop> <491C11B2.1060909@hypersurf.com> <1226612654.7178.84.camel@pasglop> <491CAA32.20307@hypersurf.com> <1226624429.7178.105.camel@pasglop> <49212D61.3080305@hypersurf.com> <1226912422.7178.228.camel@pasglop> <492145BB.7080904@hypersurf.com> Content-Type: text/plain Date: Mon, 17 Nov 2008 22:40:18 +1100 Message-Id: <1226922018.7178.237.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2008-11-17 at 02:21 -0800, Kevin Diggs wrote: > Benjamin Herrenschmidt wrote: > > > > > > That's definitely strange. I would expect the kernel to be able to get > > interrupts fast enough to service a 1200 bauds serial port. Maybe > > there's something else wrong, or an other driver causing undue interrupt > > latencies.... > > > As far as I can see the system is NOT busy. I see no evidence of excessive > interrupt loading. It does have an Adaptec 2940 u2w SCSI card, an ATI video card, > and a USB/firewire card. The SCSI card has some disks on it. The other two cards > are unused. I guess, in theory, something in my 2.6.27 kernel could be causing one > of the two unused cards to throw spurious interrupts? > > I still think the hardware is mis-behaving. That's strange. Maybe one of the drivers is occasionally hogging interrutps. Well, there may also be a bug in the code :-) One thing you can try is to disable DMA in macserial (shouldn't be hard to hack) and see if it degrades the same way. > > Out of curiosity, check that IDE properly unmasks interrupts (hdparm > > -u1 /dev/hda). > > > This is an 8600. It is SCSI only (the onboard controller is the MESH). Ah yes. > >> So, I'm on board with this approach. Since I don't really know what I am > >>doing, how do you recommend I proceed? > > > > > > Google for a document called MacTech.pdf which contains various > > documentations for bits of the ancestor of the IO chip in your machine, > > along with a description of the DBDMA engine :-) Something else you can > > do is to look at how it's properly used by other drivers such as bmac > > and look at some of the darwin source code for reference on how the HW > > works. > > > where might one find older Darwin source? Apple still has most of them back to 10.0 and even the recent ones still have an SCC serial driver afaik. Ben. > > Cheers, > > Ben. > > > > _______________________________________________ > > > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-dev