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SubjectRe: [PATCH V3 1/5] powerpc, perf: Add new BHRB related instructions for POWER8
On 04/22/2013 08:20 AM, Michael Neuling wrote:
> Michael Ellerman <michael@ellerman.id.au> wrote:
>
>> On Mon, Apr 22, 2013 at 11:13:43AM +1000, Michael Neuling wrote:
>>> Michael Ellerman <michael@ellerman.id.au> wrote:
>>>
>>>> On Thu, Apr 18, 2013 at 05:56:12PM +0530, Anshuman Khandual wrote:
>>>>> This patch adds new POWER8 instruction encoding for reading
>>>>> the BHRB buffer entries and also clearing it. Encoding for
>>>>> "clrbhrb" instruction is straight forward.
>>>>
>>>> Which is "clear branch history rolling buffer" ?
>>>>
>>>>> But "mfbhrbe"
>>>>> encoding involves reading a certain index of BHRB buffer
>>>>> into a particular GPR register.
>>>>
>>>> And "Move from branch history rolling buffer entry" ?
>>>>
>>>>> diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
>>>>> index 8752bc8..93ae5a1 100644
>>>>> --- a/arch/powerpc/include/asm/ppc-opcode.h
>>>>> +++ b/arch/powerpc/include/asm/ppc-opcode.h
>>>>> @@ -82,6 +82,7 @@
>>>>> #define __REGA0_R31 31
>>>>>
>>>>> /* sorted alphabetically */
>>>>> +#define PPC_INST_BHRBE 0x7c00025c
>>>>
>>>> I don't think you really need this, just use the literal value below.
>>>
>>> The rest of the defines in this file do this, so Anshuman's right.
>>
>> I don't see the point, but sure let's be consistent. Though in that case
>> he should do the same for PPC_CLRBHRB below.
>
> Agreed.
>

Sure, would define a new macro (PPC_INST_CLRBHRB) to encode 0x7c00035c
before using it for PPC_CLRBHRB.

> Mikey
>
>>
>>>>> @@ -297,6 +298,12 @@
>>>>> #define PPC_NAP stringify_in_c(.long PPC_INST_NAP)
>>>>> #define PPC_SLEEP stringify_in_c(.long PPC_INST_SLEEP)
>>>>>
>>>>> +/* BHRB instructions */
>>>>> +#define PPC_CLRBHRB stringify_in_c(.long 0x7c00035c)
>>>>> +#define PPC_MFBHRBE(r, n) stringify_in_c(.long PPC_INST_BHRBE | \
>>>>> + __PPC_RS(r) | \
>>>>> + (((n) & 0x1f) << 11))
>>>>
>>>> Why are you not using ___PPC_RB(n) here ?
>>>
>>> Actually, this is wrong. The number field should be 10 bits (0x3ff),
>>> not 5 (0x1f) Anshuman please fix.
>>
>> ACK.

I got it wrong, thought this as 32 instead of 1024. Would fix it.

Regards
Anshuman



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