[PATCH ] cell: enable pause(0) in cpu_idle

[Milton Miller]

Segher and I were talking on #mklinux about optimsing this.
Below is what we came up with.

On Dec 15, 2005, at 12:30 PM, Milton Miller wrote:
>>
>> BEGIN_FTR_SECTION
>> ­·······mr­·····r10,r12    /* r12 has SRR1 saved */
>> ­·······srwi­···r10,r10,16
>> ­·······andi.­··r10,r10,MSR_WAKEMASK
>> ­·······cmpwi­··r10,MSR_WAKEEE
>> ­·······beq­····hardware_interrupt_common
>> ­·······cmpwi­··r10,MSR_WAKEDEC
>> ­·······beq­····decrementer_common
>> ­·······cmpwi­··r10,MSR_WAKEMT
>> ­·······bne­····system_reset_common
>> ­·······EXCEPTION_PROLOG_COMMON(0x100, PACA_EXGEN);
>> ­·······b­······fast_exception_return
>> END_FTR_SECTION_IFSET(CPU_FTR_PAUSE_ZERO)
>> ­·······b­······system_reset_common
>>
>> Is there a simpler way to express this?
>
> Original patch:
>>>>> +/* Wake Events */
>>>>> +#define MSR_WAKEMASK	0x0038
>>>>> +#define MSR_WAKERESET	0x0038
>>>>> +#define MSR_WAKESYSERR	0x0030
>>>>> +#define MSR_WAKEEE	0x0020
>>>>> +#define MSR_WAKEMT	0x0028
>>>>> +#define MSR_WAKEDEC	0x0018
>>>>> +#define MSR_WAKETHERM	0x0010


Since we are checking 3 consecitive values,

make these be in the range 0-7
	<segher>	shift right 19 (decim)
	<segher>	rlwinm a,b,13,29,31
	<miltonm>	sub 3 recording, beq, cmp usngined 2, blt beq
	<segher>	but move the cmp an insn out


lets see if I can get this all right....

BEGIN_FTR_SECTION
	b	system_reset_common
END_FTR_SECTION_IFCLR(CPU_FTR_PAUSE_ZERO)
#if ((WAKE_MT - WAKE_DEC) != 2) || ((WAKE_EE - WAKE_DEC) != 1)
#error This optimization is broken
#endif
	rlwinm	r10,r12,32-MSR_WAKE_LG,MSR_WAKE_MASK
	subi.	r10,r10,WAKE_DEC
	cmplwi	cr7,r10,WAKE_MT-WAKE_DEC
	beq	decrementer_common
	blt	cr7,hardware_interrupt_common
	bne	cr7,system_reset_common
	EXCEPTION_PROLOG_COMMON(0x100, PACA_EXGEN);
	b	fast_exception_return