Re: [PATCH v2] powernv: Handle wakeup from idle due to SRESET

[Paul Mackerras]

On Tue, Nov 22, 2016 at 11:06:32PM +0530, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" 
> 
> The existing code doesn't handle the case when CPU which was in a
> hardware-idle state (nap,sleep,winkle on POWER8 and various stop
> states on POWER9) gets woken up due to a System Reset interrupt.
> 
> This patch checks if the CPU was woken up due to System Reset, in
> which case, after restoring the required hardware state, it jumps to
> the system reset handler.
> 
> Signed-off-by: Gautham R. Shenoy 
> ---
> v1 -> v2: Set r9,r11,r12 to CR,SRR0,SRR1 values
> before jumping to system_reset_common as expected by
> EXCEPTION_PROLOG_COMMON
> 
>  arch/powerpc/kernel/idle_book3s.S | 18 ++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/idle_book3s.S 
> b/arch/powerpc/kernel/idle_book3s.S
> index 72dac0b..06afe0e 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -353,6 +353,22 @@ ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 66); 
> \
>   ld  r3,ORIG_GPR3(r1);   /* Restore original r3 */   \
>  20:  nop;
>  
> +#define CHECK_SRESET_INTERRUPT  \
> +BEGIN_FTR_SECTION_NESTED(67);
> \
> + mfspr   r0,SPRN_SRR1;   \
> + rlwinm  r0,r0,45-31,0xf; /* Extract wake reason field (P8,9) */ \
> + cmpwi   r0,0x4;   /* System Reset ? */  \
> + bne 21f;\
> + ld  r1,PACAR1(r13); \
> + ld  r9,_CCR(r1);\
> + ld  r11,_NIP(r1);   \
> + mfspr   r12, SPRN_SRR1; \
> + b   system_reset_common ;   \
> + b   .;  /* We shouldn't return here */  \
> +FTR_SECTION_ELSE_NESTED(67); \
> + nop;\
> +ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 67); \

What's the point of the else section?

Paul.

Re: [PATCH v2] powernv: Handle wakeup from idle due to SRESET

[Paul Mackerras]

On Tue, Nov 22, 2016 at 11:06:32PM +0530, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" 
> 
> The existing code doesn't handle the case when CPU which was in a
> hardware-idle state (nap,sleep,winkle on POWER8 and various stop
> states on POWER9) gets woken up due to a System Reset interrupt.
> 
> This patch checks if the CPU was woken up due to System Reset, in
> which case, after restoring the required hardware state, it jumps to
> the system reset handler.
> 
> Signed-off-by: Gautham R. Shenoy 
> ---
> v1 -> v2: Set r9,r11,r12 to CR,SRR0,SRR1 values
> before jumping to system_reset_common as expected by
> EXCEPTION_PROLOG_COMMON
> 
>  arch/powerpc/kernel/idle_book3s.S | 18 ++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/idle_book3s.S 
> b/arch/powerpc/kernel/idle_book3s.S
> index 72dac0b..06afe0e 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -353,6 +353,22 @@ ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 66); 
> \
>   ld  r3,ORIG_GPR3(r1);   /* Restore original r3 */   \
>  20:  nop;
>  
> +#define CHECK_SRESET_INTERRUPT  \
> +BEGIN_FTR_SECTION_NESTED(67);
> \
> + mfspr   r0,SPRN_SRR1;   \
> + rlwinm  r0,r0,45-31,0xf; /* Extract wake reason field (P8,9) */ \
> + cmpwi   r0,0x4;   /* System Reset ? */  \
> + bne 21f;\
> + ld  r1,PACAR1(r13); \
> + ld  r9,_CCR(r1);\
> + ld  r11,_NIP(r1);   \
> + mfspr   r12, SPRN_SRR1; \
> + b   system_reset_common ;   \
> + b   .;  /* We shouldn't return here */  \
> +FTR_SECTION_ELSE_NESTED(67); \
> + nop;\
> +ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 67); \

What's the point of the else section?

Paul.