[RFC] Add IBM Blue Gene/Q Platform
jimix at pobox.com
Sat Dec 8 00:38:22 EST 2012
On Dec 6, 2012, at 11:54 PM, Michael Neuling <mikey at neuling.org> wrote:
>> commit 279c0615917b959a652e81f4ad0d886e2d426d85
>> Author: Jimi Xenidis <jimix at pobox.com>
>> Date: Wed Dec 5 13:43:22 2012 -0500
>> powerpc/book3e: IBM Blue Gene/Q Quad Processing eXtention (QPX)
>> This enables kernel support for the QPX extention and is intended for
>> processors that support it, usually an IBM Blue Gene processor.
>> Turning it on does not effect other processors but it does add code
>> and will quadruple the per thread save and restore area for the FPU
>> (hense the name). If you have enabled VSX it will only double the
>> Signed-off-by: Jimi Xenidis <jimix at pobox.com>
> Can you give a diagram of how the QPX registers are layed out.
> +#if defined(CONFIG_PPC_QPX)
> +#define TS_FPRWIDTH 4
> +#elif defined(CONFIG_VSX)
> Are they 256 bits wide?
Yes, this is why we nicknamed it the "Quad Hummer" :)
- 4-wide double precision FPU SIMD
- 2-wide complex SIMD
- 4R/2W register file (32x256 bits per thread)
- 32B (256 bits) datapath to/from L1 cache
> +#define QVLFDXA(QRT,RA,RB) \
> + .long (0x7c00048f | ((QRT) << 21) | ((RA) << 16) | ((RB) << 11))
> Put this in ppc-opcode.h.
> +#if defined(CONFIG_VSX) || defined(CONFIG_PPC_QPX)
> + /* they are the same MSR bit */
Ooops, you are correct, this was in the original patch.
I'll double check the work book, but it should be the architected VEC/SPV bit which is really for VMX.
I'll track it down.
> +BEGIN_FTR_SECTION \
> + SAVE_32VSRS(n,c,base); \
> +END_FTR_SECTION_IFSET(CPU_FTR_VSX); \
> +BEGIN_FTR_SECTION \
> + SAVE_32QRS(n,c,base); \
> I don't think we want to do this. We are going to end up with 64
> NOPS here somewhere.
Excellent point, NOPs are cheap on most processors but not A2 and a lot of embedded, I can wrap some branches with the FTR instead.
Do you have a concern on the code size?
> I'd like to see this patch broken into different parts.
I'm not sure how _this_ patch:
could be broken up, please advise.
> Also, have you boot tested this change on a VSX enabled box?
I can try, I may bug you for help.
Is there a commonly test (or apps) I should run?
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