linux-kernel - Re: 2.6.24-rc8 hangs at mfgpt-timer

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Date:	Tue, 22 Jan 2008 11:15:42 -0700
From:	"Jordan Crouse" <jordan.crouse@....com>
To:	"Arnd Hannemann" <hannemann@...informatik.rwth-aachen.de>
cc:	"Lars Heete" <hel@...in.de>,
	"Andres Salomon" <dilinger@...ued.net>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.24-rc8 hangs at mfgpt-timer

On 22/01/08 12:18 +0100, Arnd Hannemann wrote:
> Hi Lars,
> 
> Lars Heete schrieb:
> > Hello,
> > 
> > On Tuesday 22 January 2008 10:03:08 am Arnd Hannemann wrote:
> >> Jordan Crouse wrote:
> >>> Okay - I've been exploring a little bit more.  I talked to the TinyBIOS
> >>> developer, and he verified that TinyBIOS shouldn't use any MFGPT timers.
> >>> He also told me that the mysterious "MFGPT workaround" was in fact the
> >>> magic MFGPT erasing MSR that was in the old kernel driver.
> >>>
> >>> So with the "MFGPT workaround" turned off, TinyBIOS should be acting like
> >>> the OLPC firmware with regards to timers, yet it is not.  So that is
> >>> curious.  I think I might have identified a race condition in the code,
> >>> but I'm not 100% sure thats the same problem that the ALIX platform is
> >>> seeing.
> >>>
> >>> Anrd and others - will you please try the attached patch on your platform
> >>> with the "MFGPT workaround" turned off and mfgpts enabled, and send out
> >>> the dmesg?
> >> Of course, tinyBios version v0.99, "MFGPT workaround" turned off,
> >> CONFIG_GEODE_MFGPT_TIMER=n:
> >>
> >> [   67.369697] NET: Registered protocol family 16
> >> [   67.383059] geode-mfgpt:  IRQ MSR=0:0
> >> [   67.394058] geode-mfgpt:  NMI MSR=0:0
> >> [   67.405049] geode-mfgpt:  Unrestricted sources=0
> >> [   67.418909] geode:  8 MFGPT timers available.
> >> [   67.433211] PCI: PCI BIOS revision 2.10 entry at 0xfcd03, last bus=0
> >>
> >> same with CONFIG_GEODE_MFGPT_TIMER=y (sorry, without move printk patch):
> >>
> >> [   22.289349] NET: Registered protocol family 16
> >> [   22.302716] geode-mfgpt:  IRQ MSR=0:0
> >> [   22.313716] geode-mfgpt:  NMI MSR=0:0
> >> [   22.324704] geode-mfgpt:  Unrestricted sources=0
> >> [   22.338566] geode-mfgpt:  Registered timer 0
> >> [   22.351393] mfgpt-timer:  registering the MFGT timer as a clock event.
> >> ^^^^ Hangs here
> > I had the same problem with MFGPT Timers and alix (BIOS v0.99). I found that 
> > if you use a different interrupt than the default 7 for MFGPT (just append 
> > mfgpt_irq=8 to the kernel commandline), the timer seems to work.
> 
> Indeed.
> Strange, it works at least with mfgpt_irq=8 (rtc) and mfgpt_irq=5 (audio):

That is very unfortunate.  We must continue to investigate.

> [   21.805129] geode-mfgpt:  IRQ MSR=0:0
> [   21.816129] geode-mfgpt:  NMI MSR=0:0
> [   21.827116] geode-mfgpt:  Unrestricted sources=0
> [   21.840979] geode-mfgpt:  Registered timer 0
> [   21.853806] mfgpt-timer:  registering the MFGT timer as a clock event.
> [   21.873576] geode:  8 MFGPT timers available.
> [   21.887962] PCI: PCI BIOS revision 2.10 entry at 0xfcd03, last bus=0
> 
<snip>

> I noted that "rtc" disappeared, do I have any drawback of this?
> I assume that the mfgpt-timer cannot be shared?

No.  We figured that was the best way to go.  I don't know if there
are any technical reasons why it can't be shared, other then latency
problems.

But I would still prefer to figure out why 7 doesn't work - because there
is nothing in the hardware or kernel code that should prevent that.

Arnd - if you don't mind doing a little bit more debug work.  You've already
given us the MSRs for 0x51400020 - 0x51400023.  Can you now give us 
0x51400024-0x51400027, as well as 5140004E?  Our current working theory
is that IRQ7 (traditionally used by the LPT port) is still conflicting
somewhere.

Jordan
-- 
Jordan Crouse
Systems Software Development Engineer 
Advanced Micro Devices, Inc.


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