bug in head.S

bug in head.S

[Nathan Sheeley]

This is more or less the same message that I posted earlier, but no one 
replied.  Please at least tell me to go away ;^)

I was poking around in arch/ppc/kernel/head.S and I noticed this:

  oris  r18,r8,0x20000000@h
  oris  r21,r11,(KERNELBASE+0x20000000)@h
  mtspr DBAT2L,r18    /* N.B. 6xx (not 601) have valid */
  mtspr DBAT2U,r21    /* bit in upper BAT register */
  mtspr IBAT2L,r28
               ^^^^^^^^^^^^^^^^Wouldn't r18 make more sense here?
  mtspr IBAT2U,r21    

Has anyone tried to build/run a pmac SMP kernel with a recent (2.2.9)
version of Linux?  

    o I've got a 9500 with 2 604e/200MHz.
    o A UP kernel works fine.  
    o Compliling the same kernel with the SMP support box checked results in
      a kernel that doesn't boot on UP(a G3) or SMP(the 9500) machines. 
    o I also replaced the dual card with a single 133 MHz CPU, which also fails 
    to boot the SMP kernel.

Can I expect a SMP kernel to boot on a UP?  I thought so, although it might
be slower than a UP kernel on a UP.

The symptoms are that it gets to the point of "opening the display", which
activates the display (all white, I assume painted that way by OF), prints 
"copying OF device tree...done" and stops.  

Nathan Sheeley


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Re: bug in head.S

[Paul Mackerras]

Nathan Sheeley <nsheeley@ibmoto.com> wrote:

> I was poking around in arch/ppc/kernel/head.S and I noticed this:
> 
>   oris  r18,r8,0x20000000@h
>   oris  r21,r11,(KERNELBASE+0x20000000)@h
>   mtspr DBAT2L,r18    /* N.B. 6xx (not 601) have valid */
>   mtspr DBAT2U,r21    /* bit in upper BAT register */
>   mtspr IBAT2L,r28
>                ^^^^^^^^^^^^^^^^Wouldn't r18 make more sense here?

Yep, sure, thanks for pointing that out.

> Has anyone tried to build/run a pmac SMP kernel with a recent (2.2.9)
> version of Linux?  

I have 2.2.10 running on my 2-cpu powermac at home (it's a 7500 with a
2 x 604e 200MHz cpu card in it).  It mostly runs fine but has frozen
up on me a couple of times - I haven't tracked down why/where yet.

> Can I expect a SMP kernel to boot on a UP?  I thought so, although it might

I would have thought so, as long as it's not a 601.  The SMP kernel
uses the tlbsync instruction which isn't implemented on the 601.

Paul.

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Re: bug in head.S

[Nathan Sheeley]

> > Has anyone tried to build/run a pmac SMP kernel with a recent (2.2.9)
> > version of Linux?  
> 
> I have 2.2.10 running on my 2-cpu powermac at home (it's a 7500 with a
> 2 x 604e 200MHz cpu card in it).  It mostly runs fine but has frozen
> up on me a couple of times - I haven't tracked down why/where yet.

I pulled the MP card from the 9500, and installed it in an 8500;
where it works fine w/2.2.0.  The 9500 (even with a single CPU) 
still appears to hang just after opening the display.  Perhaps
a problem w/ the mach64 driver that only affects older versions
of the card?

Nate

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