Excerpts from Christophe Leroy's message of September 6, 2020 5:32 pm:
>
>
> Le 05/09/2020 à 19:43, Nicholas Piggin a écrit :
>> There is no need for this to be in asm, use the new intrrupt entry wrapper.
>>
>> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
>> ---
>> arch/powerpc/include/asm/interrupt.h | 14 ++++++++
>> arch/powerpc/include/asm/processor.h | 1 +
>> arch/powerpc/include/asm/thread_info.h | 6 ++++
>> arch/powerpc/kernel/exceptions-64s.S | 45 --------------------------
>> arch/powerpc/kernel/idle_book3s.S | 4 +++
>> 5 files changed, 25 insertions(+), 45 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/interrupt.h
>> b/arch/powerpc/include/asm/interrupt.h
>> index 3ae3d2f93b61..acfcc7d5779b 100644
>> --- a/arch/powerpc/include/asm/interrupt.h
>> +++ b/arch/powerpc/include/asm/interrupt.h
>> @@ -8,6 +8,16 @@
>> #include <asm/ftrace.h>
>> #include <asm/runlatch.h>
>>
>> +static inline void nap_adjust_return(struct pt_regs *regs)
>> +{
>> +#ifdef CONFIG_PPC_970_NAP
>
> Avoid #ifdef, you can use IS_ENABLED(CONFIG_PPC_970_NAP) in the 'if' below
Yeah I guess.
>> + if (test_thread_local_flags(_TLF_NAPPING)) {
>> + clear_thread_local_flags(_TLF_NAPPING);
>> + regs->nip = (unsigned long)power4_idle_nap_return;
>> + }
>> +#endif
>> +}
>> +
>> #ifdef CONFIG_PPC_BOOK3S_64
>> static inline void interrupt_enter_prepare(struct pt_regs *regs)
>> {
>> @@ -33,6 +43,8 @@ static inline void interrupt_async_enter_prepare(struct
>> pt_regs *regs)
>> if (cpu_has_feature(CPU_FTR_CTRL) &&
>> !test_thread_local_flags(_TLF_RUNLATCH))
>> __ppc64_runlatch_on();
>> +
>> + nap_adjust_return(regs);
>> }
>>
>> #else /* CONFIG_PPC_BOOK3S_64 */
>> @@ -72,6 +84,8 @@ static inline void interrupt_nmi_enter_prepare(struct
>> pt_regs *regs, struct inte
>>
>> this_cpu_set_ftrace_enabled(0);
>>
>> + nap_adjust_return(regs);
>> +
>> nmi_enter();
>> }
>>
>> diff --git a/arch/powerpc/include/asm/processor.h
>> b/arch/powerpc/include/asm/processor.h
>> index ed0d633ab5aa..3da1dba91386 100644
>> --- a/arch/powerpc/include/asm/processor.h
>> +++ b/arch/powerpc/include/asm/processor.h
>> @@ -424,6 +424,7 @@ extern unsigned long isa300_idle_stop_mayloss(unsigned
>> long psscr_val);
>> extern unsigned long isa206_idle_insn_mayloss(unsigned long type);
>> #ifdef CONFIG_PPC_970_NAP
>> extern void power4_idle_nap(void);
>> +extern void power4_idle_nap_return(void);
>
> Please please please, 'extern' keyword is pointless and deprecated for
> function prototypes. Don't add new ones.
>
> Also, put it outside the #ifdef, so that you can use IS_ENABLED()
> instead of #ifdef when using it.
I just copy paste and forget to remove it. I expect someone will do a
"cleanup" patch to get rid of them in one go, I find a random assortment
of extern and not extern to be even uglier :(
>> #endif
>>
>> extern unsigned long cpuidle_disable;
>> diff --git a/arch/powerpc/include/asm/thread_info.h
>> b/arch/powerpc/include/asm/thread_info.h
>> index ca6c97025704..9b15f7edb0cb 100644
>> --- a/arch/powerpc/include/asm/thread_info.h
>> +++ b/arch/powerpc/include/asm/thread_info.h
>> @@ -156,6 +156,12 @@ void arch_setup_new_exec(void);
>>
>> #ifndef __ASSEMBLY__
>>
>> +static inline void clear_thread_local_flags(unsigned int flags)
>> +{
>> + struct thread_info *ti = current_thread_info();
>> + ti->local_flags &= ~flags;
>> +}
>> +
>> static inline bool test_thread_local_flags(unsigned int flags)
>> {
>> struct thread_info *ti = current_thread_info();
>> diff --git a/arch/powerpc/kernel/exceptions-64s.S
>> b/arch/powerpc/kernel/exceptions-64s.S
>> index 227bad3a586d..1db6b3438c88 100644
>> --- a/arch/powerpc/kernel/exceptions-64s.S
>> +++ b/arch/powerpc/kernel/exceptions-64s.S
>> @@ -692,25 +692,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
>> ld r1,GPR1(r1)
>> .endm
>>
>> -/*
>> - * When the idle code in power4_idle puts the CPU into NAP mode,
>> - * it has to do so in a loop, and relies on the external interrupt
>> - * and decrementer interrupt entry code to get it out of the loop.
>> - * It sets the _TLF_NAPPING bit in current_thread_info()->local_flags
>> - * to signal that it is in the loop and needs help to get out.
>> - */
>> -#ifdef CONFIG_PPC_970_NAP
>> -#define FINISH_NAP \
>> -BEGIN_FTR_SECTION \
>> - ld r11, PACA_THREAD_INFO(r13); \
>> - ld r9,TI_LOCAL_FLAGS(r11); \
>> - andi. r10,r9,_TLF_NAPPING; \
>> - bnel power4_fixup_nap; \
>> -END_FTR_SECTION_IFSET(CPU_FTR_CAN_NAP)
>> -#else
>> -#define FINISH_NAP
>> -#endif
>> -
>> /*
>> * There are a few constraints to be concerned with.
>> * - Real mode exceptions code/data must be located at their physical
>> location.
>> @@ -1250,7 +1231,6 @@ EXC_COMMON_BEGIN(machine_check_common)
>> */
>> GEN_COMMON machine_check
>>
>> - FINISH_NAP
>> /* Enable MSR_RI when finished with PACA_EXMC */
>> li r10,MSR_RI
>> mtmsrd r10,1
>> @@ -1572,7 +1552,6 @@ EXC_VIRT_BEGIN(hardware_interrupt, 0x4500, 0x100)
>> EXC_VIRT_END(hardware_interrupt, 0x4500, 0x100)
>> EXC_COMMON_BEGIN(hardware_interrupt_common)
>> GEN_COMMON hardware_interrupt
>> - FINISH_NAP
>> addi r3,r1,STACK_FRAME_OVERHEAD
>> bl do_IRQ
>> b interrupt_return
>> @@ -1757,7 +1736,6 @@ EXC_VIRT_BEGIN(decrementer, 0x4900, 0x80)
>> EXC_VIRT_END(decrementer, 0x4900, 0x80)
>> EXC_COMMON_BEGIN(decrementer_common)
>> GEN_COMMON decrementer
>> - FINISH_NAP
>> addi r3,r1,STACK_FRAME_OVERHEAD
>> bl timer_interrupt
>> b interrupt_return
>> @@ -1842,7 +1820,6 @@ EXC_VIRT_BEGIN(doorbell_super, 0x4a00, 0x100)
>> EXC_VIRT_END(doorbell_super, 0x4a00, 0x100)
>> EXC_COMMON_BEGIN(doorbell_super_common)
>> GEN_COMMON doorbell_super
>> - FINISH_NAP
>> addi r3,r1,STACK_FRAME_OVERHEAD
>> #ifdef CONFIG_PPC_DOORBELL
>> bl doorbell_exception
>> @@ -2196,7 +2173,6 @@ EXC_COMMON_BEGIN(hmi_exception_early_common)
>>
>> EXC_COMMON_BEGIN(hmi_exception_common)
>> GEN_COMMON hmi_exception
>> - FINISH_NAP
>> addi r3,r1,STACK_FRAME_OVERHEAD
>> bl handle_hmi_exception
>> b interrupt_return
>> @@ -2225,7 +2201,6 @@ EXC_VIRT_BEGIN(h_doorbell, 0x4e80, 0x20)
>> EXC_VIRT_END(h_doorbell, 0x4e80, 0x20)
>> EXC_COMMON_BEGIN(h_doorbell_common)
>> GEN_COMMON h_doorbell
>> - FINISH_NAP
>> addi r3,r1,STACK_FRAME_OVERHEAD
>> #ifdef CONFIG_PPC_DOORBELL
>> bl doorbell_exception
>> @@ -2258,7 +2233,6 @@ EXC_VIRT_BEGIN(h_virt_irq, 0x4ea0, 0x20)
>> EXC_VIRT_END(h_virt_irq, 0x4ea0, 0x20)
>> EXC_COMMON_BEGIN(h_virt_irq_common)
>> GEN_COMMON h_virt_irq
>> - FINISH_NAP
>> addi r3,r1,STACK_FRAME_OVERHEAD
>> bl do_IRQ
>> b interrupt_return
>> @@ -2304,7 +2278,6 @@ EXC_VIRT_BEGIN(performance_monitor, 0x4f00, 0x20)
>> EXC_VIRT_END(performance_monitor, 0x4f00, 0x20)
>> EXC_COMMON_BEGIN(performance_monitor_common)
>> GEN_COMMON performance_monitor
>> - FINISH_NAP
>> addi r3,r1,STACK_FRAME_OVERHEAD
>> bl performance_monitor_exception
>> b interrupt_return
>> @@ -3032,24 +3005,6 @@ USE_FIXED_SECTION(virt_trampolines)
>> __end_interrupts:
>> DEFINE_FIXED_SYMBOL(__end_interrupts)
>>
>> -#ifdef CONFIG_PPC_970_NAP
>> - /*
>> - * Called by exception entry code if _TLF_NAPPING was set, this clears
>> - * the NAPPING flag, and redirects the exception exit to
>> - * power4_fixup_nap_return.
>> - */
>> - .globl power4_fixup_nap
>> -EXC_COMMON_BEGIN(power4_fixup_nap)
>> - andc r9,r9,r10
>> - std r9,TI_LOCAL_FLAGS(r11)
>> - LOAD_REG_ADDR(r10, power4_idle_nap_return)
>> - std r10,_NIP(r1)
>> - blr
>> -
>> -power4_idle_nap_return:
>> - blr
>> -#endif
>> -
>> CLOSE_FIXED_SECTION(real_vectors);
>> CLOSE_FIXED_SECTION(real_trampolines);
>> CLOSE_FIXED_SECTION(virt_vectors);
>> diff --git a/arch/powerpc/kernel/idle_book3s.S
>> b/arch/powerpc/kernel/idle_book3s.S
>> index 22f249b6f58d..27d2e6a72ec9 100644
>> --- a/arch/powerpc/kernel/idle_book3s.S
>> +++ b/arch/powerpc/kernel/idle_book3s.S
>> @@ -201,4 +201,8 @@ _GLOBAL(power4_idle_nap)
>> mtmsrd r7
>> isync
>> b 1b
>> +
>> + .globl power4_idle_nap_return
>> +power4_idle_nap_return:
>> + blr
>
> Can't this be written in C somewhere ?
Yes I think so if you did the entire power4_idle_nap function in C and
used inline asm for the mtmsrd and fixup label (basically the same way
as copy user exceptions return to a fixup location).
You have to return to the same C function of course because you can't
control the stack otherwise. But I don't care too much about avoiding
an extra function call/return here, all the important stuff is in C now.
Thanks,
Nick
