Subject: Re: [PATCH 6/8] powerpc/64s: idle expand usable core idle state bits

From: Gautham R Shenoy <[email-masked]>
Date: Thu, 16 Mar 2017 17:40:51 +0530

Hi Nick,

On Tue, Mar 14, 2017 at 07:23:47PM +1000, Nicholas Piggin wrote:
> In preparation for adding more bits to the core idle state word,
> move the lock bit up, and unlock by flipping the lock bit rather
> than masking off all but the thread bits.
> 
> Add branch hints for atomic operations while we're here.

Looks good.

Reviewed-by: Gautham R. Shenoy <[email-masked]>

> 
> Signed-off-by: Nicholas Piggin <[email-masked]>
> ---
>  arch/powerpc/include/asm/cpuidle.h |  4 ++--
>  arch/powerpc/kernel/idle_book3s.S  | 33 +++++++++++++++++----------------
>  2 files changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h
> index 155731557c9b..b9d9f960dffd 100644
> --- a/arch/powerpc/include/asm/cpuidle.h
> +++ b/arch/powerpc/include/asm/cpuidle.h
> @@ -7,8 +7,8 @@
>  #define PNV_THREAD_NAP                  1
>  #define PNV_THREAD_SLEEP                2
>  #define PNV_THREAD_WINKLE               3
> -#define PNV_CORE_IDLE_LOCK_BIT          0x100
> -#define PNV_CORE_IDLE_THREAD_BITS       0x0FF
> +#define PNV_CORE_IDLE_LOCK_BIT          0x10000000
> +#define PNV_CORE_IDLE_THREAD_BITS       0x000000FF
> 
>  /*
>   * ============================ NOTE =================================
> diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
> index 9bdfba75a5e7..1c91dc35c559 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -95,12 +95,12 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
>  core_idle_lock_held:
>  	HMT_LOW
>  3:	lwz	r15,0(r14)
> -	andi.   r15,r15,PNV_CORE_IDLE_LOCK_BIT
> +	andis.	r15,r15,PNV_CORE_IDLE_LOCK_BIT@h
>  	bne	3b
>  	HMT_MEDIUM
>  	lwarx	r15,0,r14
> -	andi.	r9,r15,PNV_CORE_IDLE_LOCK_BIT
> -	bne	core_idle_lock_held
> +	andis.	r9,r15,PNV_CORE_IDLE_LOCK_BIT@h
> +	bne-	core_idle_lock_held
>  	blr
> 
>  /*
> @@ -213,8 +213,8 @@ pnv_enter_arch207_idle_mode:
>  lwarx_loop1:
>  	lwarx	r15,0,r14
> 
> -	andi.   r9,r15,PNV_CORE_IDLE_LOCK_BIT
> -	bnel	core_idle_lock_held
> +	andis.	r9,r15,PNV_CORE_IDLE_LOCK_BIT@h
> +	bnel-	core_idle_lock_held
> 
>  	andc	r15,r15,r7			/* Clear thread bit */
> 
> @@ -241,7 +241,7 @@ common_enter: /* common code for all the threads entering sleep or winkle */
>  	IDLE_STATE_ENTER_SEQ_NORET(PPC_SLEEP)
> 
>  fastsleep_workaround_at_entry:
> -	ori	r15,r15,PNV_CORE_IDLE_LOCK_BIT
> +	oris	r15,r15,PNV_CORE_IDLE_LOCK_BIT@h
>  	stwcx.	r15,0,r14
>  	bne-	lwarx_loop1
>  	isync
> @@ -251,10 +251,10 @@ fastsleep_workaround_at_entry:
>  	li	r4,1
>  	bl	opal_config_cpu_idle_state
> 
> -	/* Clear Lock bit */
> -	li	r0,0
> +	/* Unlock */
> +	xoris	r15,r15,PNV_CORE_IDLE_LOCK_BIT@h
>  	lwsync
> -	stw	r0,0(r14)
> +	stw	r15,0(r14)
>  	b	common_enter
> 
>  enter_winkle:
> @@ -302,8 +302,8 @@ power_enter_stop:
> 
>  lwarx_loop_stop:
>  	lwarx   r15,0,r14
> -	andi.   r9,r15,PNV_CORE_IDLE_LOCK_BIT
> -	bnel    core_idle_lock_held
> +	andis.	r9,r15,PNV_CORE_IDLE_LOCK_BIT@h
> +	bnel-	core_idle_lock_held
>  	andc    r15,r15,r7                      /* Clear thread bit */
> 
>  	stwcx.  r15,0,r14
> @@ -492,7 +492,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
>  	ld	r14,PACA_CORE_IDLE_STATE_PTR(r13)
>  lwarx_loop2:
>  	lwarx	r15,0,r14
> -	andi.	r9,r15,PNV_CORE_IDLE_LOCK_BIT
> +	andis.	r9,r15,PNV_CORE_IDLE_LOCK_BIT@h
>  	/*
>  	 * Lock bit is set in one of the 2 cases-
>  	 * a. In the sleep/winkle enter path, the last thread is executing
> @@ -501,9 +501,10 @@ lwarx_loop2:
>  	 * workaround undo code or resyncing timebase or restoring context
>  	 * In either case loop until the lock bit is cleared.
>  	 */
> -	bnel	core_idle_lock_held
> +	bnel-	core_idle_lock_held
> 
> -	cmpwi	cr2,r15,0
> +	andi.	r9,r15,PNV_CORE_IDLE_THREAD_BITS
> +	cmpwi	cr2,r9,0
> 
>  	/*
>  	 * At this stage
> @@ -512,7 +513,7 @@ lwarx_loop2:
>  	 * cr4 - gt or eq if waking up from complete hypervisor state loss.
>  	 */
> 
> -	ori	r15,r15,PNV_CORE_IDLE_LOCK_BIT
> +	oris	r15,r15,PNV_CORE_IDLE_LOCK_BIT@h
>  	stwcx.	r15,0,r14
>  	bne-	lwarx_loop2
>  	isync
> @@ -602,7 +603,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
>  	mtspr	SPRN_WORC,r4
> 
>  clear_lock:
> -	andi.	r15,r15,PNV_CORE_IDLE_THREAD_BITS
> +	xoris	r15,r15,PNV_CORE_IDLE_LOCK_BIT@h
>  	lwsync
>  	stw	r15,0(r14)
> 
> -- 
> 2.11.0
>