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

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Date:	Tue, 22 Jan 2008 12:18:56 +0100
From:	Arnd Hannemann <hannemann@...informatik.rwth-aachen.de>
To:	Lars Heete <hel@...in.de>
CC:	Jordan Crouse <jordan.crouse@....com>,
	Andres Salomon <dilinger@...ued.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.24-rc8 hangs at mfgpt-timer

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):

[   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


/proc/interrupts with mfgpt_irq=5:
           CPU0
  0:         48    XT-PIC-XT        timer
  2:          0    XT-PIC-XT        cascade
  4:        674    XT-PIC-XT        serial
  5:      13706    XT-PIC-XT        mfgpt-timer
  8:          3    XT-PIC-XT        rtc
 10:      57137    XT-PIC-XT        eth0
 15:          1    XT-PIC-XT        ehci_hcd:usb1, ohci_hcd:usb2
NMI:          0   Non-maskable interrupts
TRM:          0   Thermal event interrupts
SPU:          0   Spurious interrupts
ERR:          0

/proc/interrupts with mfgpt_irq=8:
           CPU0
  0:         48    XT-PIC-XT        timer
  2:          0    XT-PIC-XT        cascade
  4:       2511    XT-PIC-XT        serial
  8:      29061    XT-PIC-XT        mfgpt-timer
 10:      60701    XT-PIC-XT        eth0
 15:          1    XT-PIC-XT        ehci_hcd:usb1, ohci_hcd:usb2
NMI:          0   Non-maskable interrupts
TRM:          0   Thermal event interrupts
SPU:          0   Spurious interrupts
ERR:          0

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

> 
> CPU0
>   0:         33    XT-PIC-XT        timer
>   2:          0    XT-PIC-XT        cascade
>   4:       1662    XT-PIC-XT        serial
>   8:        766    XT-PIC-XT        mfgpt-timer
>  14:        473    XT-PIC-XT        libata
> NMI:          0
> ERR:          0
> 
> 
>>> This will give us some debug information that I can use to ensure that
>>> the interrupts are set up correctly.  You can leave the timer tick
>>> disabled if you want.
>>>
>>>
>>> Thanks,
>>> Jordan
>> Arnd
> 
> Lars
>

Thanks for the hint!
Arnd
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