[RFC][PATCH v4] powerpc/mm: e300c2/c3/c4 TLB errata workaround

[Kumar Gala]

On Mar 16, 2009, at 10:02 AM, David Jander wrote:

>
> Ok, I was analysing your code (which seems much more compact than  
> mine):
>
> On Monday 16 March 2009 14:02:18 Kumar Gala wrote:
>> [...]
>> --- a/arch/powerpc/kernel/head_32.S
>> +++ b/arch/powerpc/kernel/head_32.S
>> @@ -587,9 +587,19 @@ DataLoadTLBMiss:
>> 	ori	r1,r1,0xe04		/* clear out reserved bits */
>> 	andc	r1,r0,r1		/* PP = user? (rw&dirty? 2: 3): 0 */
>> 	mtspr	SPRN_RPA,r1
>> +	mfspr	r2,SPRN_SRR1		/* Need to restore CR0 */
>> +	mtcrf	0x80,r2
>> +BEGIN_MMU_FTR_SECTION
>> +	li	r0,1
>> +	lwz	r1,sw_way_lru at l(0)
>> +	rlwinm	r3,r3,19,25,29		/* Get Address bits 19:15 */
>
> This should be 'rlwinm	r3,r3,17,27,31' now, since you address bits,  
> not ints.

was just copying/pasting what you had :)

> Note that you are trashing r3 (SPRN_DMISS) here!

good catch..

>> +	slw	r0,r0,r3
>> +	xor	r1,r0,r1
>> +	srw	r0,r1,r3
>> +	stw	r1,sw_way_lru at l(0)
>> +	rlwimi	r2,r0,31-14,14,14
>> +END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
>> 	tlbld	r3
>
> And now you load r3 into the tlb, is this right? It doesn't seem  
> right to
> me....

correct.. I wasn't thinking about the fact that tlbld was using r3.

- k