linux-kernel - Re: [PATCH v7 07/11] powerpc/powernv: Add platform support for stop instruction

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Message-ID: <1467944442.27479.155.camel@neuling.org>
Date:	Fri, 08 Jul 2016 12:20:42 +1000
From:	Michael Neuling <mikey@...ling.org>
To:	"Shreyas B. Prabhu" <shreyas@...ux.vnet.ibm.com>,
	mpe@...erman.id.au
Cc:	benh@....ibm.com, paulus@...abs.org, ego@...ux.vnet.ibm.com,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	maddy@...ux.vnet.ibm.com
Subject: Re: [PATCH v7 07/11] powerpc/powernv: Add platform support for stop
 instruction


> diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h
> index d2f99ca..3d7fc06 100644
> --- a/arch/powerpc/include/asm/cpuidle.h
> +++ b/arch/powerpc/include/asm/cpuidle.h
> @@ -13,6 +13,8 @@
>  #ifndef __ASSEMBLY__
>  extern u32 pnv_fastsleep_workaround_at_entry[];
>  extern u32 pnv_fastsleep_workaround_at_exit[];
> +
> +extern u64 pnv_first_deep_stop_state;

mpe asked a question about this which you neither answered or addressed.
"Should this have some safe initial value?"

I'm thinking we could do this which is what you have in the init call.
   u64 pnv_first_deep_stop_state = MAX_STOP_STATE;


> @@ -439,7 +540,18 @@ timebase_resync:
>  	 */
>  	bne	cr4,clear_lock
>  
> -	/* Restore per core state */
> +	/*
> +	 * First thread in the core to wake up and its waking up with
> +	 * complete hypervisor state loss. Restore per core hypervisor
> +	 * state.
> +	 */
> +BEGIN_FTR_SECTION
> +	ld	r4,_PTCR(r1)
> +	mtspr	SPRN_PTCR,r4
> +	ld	r4,_RPR(r1)
> +	mtspr	SPRN_RPR,r4

RPR looks wrong here.  This should be on POWER8 too.

This has changed since v6 and not noted in the v7 comments.  Why are you
changing this now?

> +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
> +
>  	ld	r4,_TSCR(r1)
>  	mtspr	SPRN_TSCR,r4
>  	ld	r4,_WORC(r1)
> @@ -461,9 +573,7 @@ common_exit:
>  
>  	/* Waking up from winkle */
>  
> -	/* Restore per thread state */
> -	bl	__restore_cpu_power8
> -
> +BEGIN_MMU_FTR_SECTION
>  	/* Restore SLB  from PACA */
>  	ld	r8,PACA_SLBSHADOWPTR(r13)
>  
> @@ -477,6 +587,9 @@ common_exit:
>  	slbmte	r6,r5
>  1:	addi	r8,r8,16
>  	.endr
> +END_MMU_FTR_SECTION_IFCLR(MMU_FTR_RADIX)
> +
> +	/* Restore per thread state */

This FTR section is too big  It ends up at 25 instructions with the loop.
Probably better like this:

BEGIN_MMU_FTR_SECTION
	b	no_segments
END_MMU_FTR_SECTION_IFSET(MMU_FTR_RADIX)
	/* Restore SLB  from PACA */
	ld	r8,PACA_SLBSHADOWPTR(r13)

	.rept	SLB_NUM_BOLTED
	li	r3, SLBSHADOW_SAVEAREA
	LDX_BE	r5, r8, r3
	addi	r3, r3, 8
	LDX_BE	r6, r8, r3
	andis.	r7,r5,SLB_ESID_V@h
	beq	1f
	slbmte	r6,r5
1:	addi	r8,r8,16
	.endr

no_segments: