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Subject: Re: [PATCH] powerpc: Fix PowerPC 750CL CPU features
From: Josh Boyer <jwboyer@linux.vnet.ibm.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
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	<aeef7937e978aec33074251c48dca389@kernel.crashing.org>
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Date: Thu, 12 Apr 2007 12:10:56 -0500
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On Thu, 2007-04-12 at 18:41 +0200, Segher Boessenkool wrote:
> > PowerPC 750CL has high BATs.  The patch below sets cpu_features to 
> > match that.
> > Without it, the original firmware mappings in the high BATs aren't 
> > cleared
> > which can cause "odd" address translations to occur.
> 
> > -		.cpu_features		= CPU_FTRS_750,
> > +		.cpu_features		= CPU_FTRS_750GX,
> 
> The difference between these two is
> 
> #define CPU_FTRS_750GX  (CPU_FTR_DUAL_PLL_750FX | CPU_FTR_HAS_HIGH_BATS)
> #define CPU_FTRS_750    (CPU_FTR_COMMON)
> 
> 750GX excludes COMMON, which seems like a bug.  With

CPU_FTR_COMMON is actually a nop in this case anyway.  It should
probably be listed for "completeness", but it's defined to be 0 so it
doesn't really do anything.

> your change, 750CL uses DUAL_PLL_750FX; does it actually
> have that feature?

No, it doesn't, I missed that in the GX feature list.  Good catch.

> 
> Either way, it seems a good idea to create a CPU_FTRS_750CL,
> the CL is an evolution of the CX, not the FX/GX (in name
> at least, dunno about the gory details).

I can do that, or I can just do:

CPU_FTRS_750 | CPU_FTR_HAS_HIGH_BATS

> 
> > -		.cpu_setup		= __setup_cpu_750cx,
> > +		.cpu_setup		= __setup_cpu_750fx,
> 
> Same thing here.  Are you sure 750CL doesn't need
> the NAP workaround?  [Is anyone sure the 750CX
> actually needs it -- the comment in cpu_setup_6xx.S
> doesn't instill much confidence.]

This should be fine.

I'll send out a newer version, and fixup the description with the
comment Milton made.

josh