Re: [PATCH 18/18] powerpc/64s: move power4 idle entirely to C
From: Christophe Leroy <hidden>
Date: 2020-11-07 09:45:25
Le 05/11/2020 à 15:34, Nicholas Piggin a écrit :
Christophe asked about doing this, most of the code is still in asm but maybe it's slightly nicer? I don't know if it's worthwhile.
Heu... I don't think I was asking for that, but why not, see later comments.
At first I was just asking to write the following in C:
+
+ .globl power4_idle_nap_return
+power4_idle_nap_return:
+ blr
In extenso, instead of the above do somewhere something like:
void power4_idle_nap_return(void)
{
}
quoted hunk ↗ jump to hunk
--- arch/powerpc/kernel/idle.c | 25 ++++++++++++++++++++----- arch/powerpc/kernel/idle_book3s.S | 22 ---------------------- 2 files changed, 20 insertions(+), 27 deletions(-)diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c index ae0e2632393d..849e77a45915 100644 --- a/arch/powerpc/kernel/idle.c +++ b/arch/powerpc/kernel/idle.c@@ -72,6 +72,9 @@ int powersave_nap; #ifdef CONFIG_PPC_970_NAP void power4_idle(void) { + unsigned long msr_idle = MSR_KERNEL|MSR_EE|MSR_POW; + unsigned long tmp1, tmp2; + if (!cpu_has_feature(CPU_FTR_CAN_NAP)) return;@@ -84,13 +87,25 @@ void power4_idle(void) if (cpu_has_feature(CPU_FTR_ALTIVEC)) asm volatile("DSSALL ; sync" ::: "memory"); - power4_idle_nap(); - + asm volatile( +" ld %0,PACA_THREAD_INFO(r13) \n" +" ld %1,TI_LOCAL_FLAGS(%0) \n" +" ori %1,%1,_TLF_NAPPING \n" +" std %1,TI_LOCAL_FLAGS(%0) \n"
Can't this just be: current_thread_info()->local_flags |= _TLF_NAPPING;
/* - * power4_idle_nap returns with interrupts enabled (soft and hard). - * to our caller with interrupts enabled (soft and hard). Our caller - * can cope with either interrupts disabled or enabled upon return. + * NAPPING bit is set, from this point onward nap_adjust_return() + * will cause interrupts to return to power4_idle_nap_return. */ +"1: sync \n" +" isync \n" +" mtmsrd %2 \n" +" isync \n" +" b 1b \n"
And this:
for (;;) {
mb();
isync();
mtmsr(MSR_KERNEL|MSR_EE|MSR_POW);
isync();
}
+" .globl power4_idle_nap_return \n" +"power4_idle_nap_return: \n" + : "=r"(tmp1), "=r"(tmp2) + : "r"(msr_idle) + ); } #endif
Christophe