Re: [PATCH v1 1/3] sparc64: correctly recognise M7 cpu type

[Bob Picco <bpicco@meloft.net>]

Hi,
David Miller wrote:	[Sun Aug 24 2014, 02:43:11AM EDT]
> From: Allen Pais <allen.pais@oracle.com>
> Date: Sun, 24 Aug 2014 11:49:29 +0530
> 
> > David,
> >> 
> >>> @@ -414,6 +414,8 @@ sun4v_chip_type:
> >>>  	cmp	%g2, 'T'
> >>>  	be,pt	%xcc, 70f
> >>>  	 cmp	%g2, 'M'
> >>> +	be,pt	%xcc, 71f
> >>> +	 nop
> >>>  	bne,pn	%xcc, 49f
> >>>  	 nop
> >> 
> >> This code block is supposed to fallthrough when %g2 is 'M' so that
> >> we accept all of "{T,M}345..." but your change is breaking that
> >> such that we will now only accept "M" as a prefix for "7".
> >> 
> >> That's a regression.
> >> 
> >> All you have to do is add the new comparison against '7' in the
> >> "70:" label code block, and you're done.
> >> 
> > 
> >  When we are on this topic, here's a patch that attempts to simplify 
> > cpu detection. 
> > 
> > Here's a quick diff.
> 
> You can't call C code until you've cleared the BSS, you can't clear
> the BSS until you hook up the proper optimized routines, you can't
> hook up the proper optimized routined until you know the cpu type.
I'm aware of BSS and cpu initialization routines. Many issues are subtle
until paging_init finishes.

What BSS does this code touch or reference? None that I'm aware of.

The code is executing on OBP stack and the kernel has been remapped and
doesn't require PIC address manipulation any longer. Your only assumptions
should be OBP handling register window events and accessing compile time
initialized data. BSS is taboo for the reason you state.

One obviously has to be VERY careful. The "VERY" part is true of all code
here. Should there be fear of strcmp then implement it in simple "C" and name
it "boot_strcmp".

Perhaps I've missed an issue.

thanx,

bob
> 
> I would have done this years ago otherwise.
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