linux-kernel - Re: [PATCH v2 4/9] powerpc/powernv: Make power7_powersave

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Date:	Wed, 18 May 2016 12:21:17 +0530
From:	Shreyas B Prabhu <shreyas@...ux.vnet.ibm.com>
To:	ego@...ux.vnet.ibm.com
CC:	mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
	paulus@...abs.org, linux-kernel@...r.kernel.org, mikey@...ling.org
Subject: Re: [PATCH v2 4/9] powerpc/powernv: Make power7_powersave_common
 more generic



On 05/18/2016 12:07 PM, Gautham R Shenoy wrote:
> Hi Shreyas,
> 
> On Tue, May 03, 2016 at 01:54:33PM +0530, Shreyas B. Prabhu wrote:
>> power7_powersave_common does common steps needed before entering idle
>> state and eventually changes MSR to MSR_IDLE and does rfid to
>> power7_enter_nap_mode.
>>
>> Make it more generic by passing the rfid address as a function parameter.
>> Also make function name more generic.
> 
> [..snip..]
> 
>>
>>  _GLOBAL(power7_winkle)
>> -	li	r3,3
>> +	li	r3,PNV_THREAD_WINKLE
> 
> This particular change above can go as an independent patch.

Okay.
> 
>>
>>  _GLOBAL(power7_wakeup_tb_loss)
>> diff --git a/arch/powerpc/kernel/idle_power_common.S b/arch/powerpc/kernel/idle_power_common.S
>> index 05954ae..ff7a541 100644
>> --- a/arch/powerpc/kernel/idle_power_common.S
>> +++ b/arch/powerpc/kernel/idle_power_common.S
>> @@ -21,8 +21,10 @@
>>   * To check IRQ_HAPPENED in r4
>>   * 	0 - don't check
>>   * 	1 - check
>> + *
>> + * Address to 'rfid' to in r5
>>   */
>> -_GLOBAL(power7_powersave_common)
>> +_GLOBAL(power_powersave_common)
>>  	/* Use r3 to pass state nap/sleep/winkle */
>>  	/* NAP is a state loss, we create a regs frame on the
>>  	 * stack, fill it up with the state we care about and
>> @@ -79,13 +81,12 @@ _GLOBAL(power7_powersave_common)
>>  	 * because as soon as we do that, another thread can switch
>>  	 * the MMU context to the guest.
>>  	 */
>> -	LOAD_REG_IMMEDIATE(r5, MSR_IDLE)
>> +	LOAD_REG_IMMEDIATE(r7, MSR_IDLE)
>>  	li	r6, MSR_RI
>>  	andc	r6, r9, r6
>> -	LOAD_REG_ADDR(r7, power7_enter_nap_mode)
>>  	mtmsrd	r6, 1		/* clear RI before setting SRR0/1 */
>> -	mtspr	SPRN_SRR0, r7
>> -	mtspr	SPRN_SRR1, r5
>> +	mtspr	SPRN_SRR0, r5
>> +	mtspr	SPRN_SRR1, r7
>>  	rfid
>>  	/* No return */
> 
> Any particular reason why you swapped the roles of r5 and r7 ?
> 

With this patch, r5 which is the third parameter to
power_powersave_common contains the return address that needs to be
written to SRR0. So here I'm keeping r5 unaltered and using r7 for the MSR.

Thanks,
Shreyas