Commit ed0bc98f authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/64s: Reimplement power4_idle code in C 



This implements the tricky tracing and soft irq handling bits in C,
leaving the low level bit to asm.

A functional difference is that this redirects the interrupt exit to
a return stub to execute blr, rather than the lr address itself. This
is probably barely measurable on real hardware, but it keeps the link
stack balanced.

Tested with QEMU.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
[mpe: Move power4_fixup_nap back into exceptions-64s.S]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190711022404.18132-1-npiggin@gmail.com
parent 30e813cf

arch/powerpc/include/asm/processor.h

+3 −0
Original line number Diff line number Diff line
@@ -412,6 +412,9 @@ static inline unsigned long get_clean_sp(unsigned long sp, int is_32) 
extern unsigned long isa300_idle_stop_noloss(unsigned long psscr_val);

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);

#endif



extern unsigned long cpuidle_disable;

enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};

arch/powerpc/kernel/Makefile

+1 −2
Original line number Diff line number Diff line
@@ -62,8 +62,7 @@ obj-$(CONFIG_PPC_BOOK3E_64) += exceptions-64e.o idle_book3e.o 
obj-$(CONFIG_PPC_BARRIER_NOSPEC) += security.o

obj-$(CONFIG_PPC64)		+= vdso64/

obj-$(CONFIG_ALTIVEC)		+= vecemu.o

obj-$(CONFIG_PPC_970_NAP)	+= idle_power4.o

obj-$(CONFIG_PPC_P7_NAP)	+= idle_book3s.o

obj-$(CONFIG_PPC_BOOK3S_IDLE)	+= idle_book3s.o

procfs-y			:= proc_powerpc.o

obj-$(CONFIG_PROC_FS)		+= $(procfs-y)

rtaspci-$(CONFIG_PPC64)-$(CONFIG_PCI)	:= rtas_pci.o

arch/powerpc/kernel/exceptions-64s.S

+11 −2
Original line number Diff line number Diff line
@@ -2208,11 +2208,20 @@ __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)

	ld	r10,_LINK(r1)		/* make idle task do the */

	std	r10,_NIP(r1)		/* equivalent of a blr */

	LOAD_REG_ADDR(r10, power4_idle_nap_return)

	std	r10,_NIP(r1)

	blr



power4_idle_nap_return:

	blr

#endif

arch/powerpc/kernel/idle.c

+25 −0
Original line number Diff line number Diff line
@@ -77,6 +77,31 @@ void arch_cpu_idle(void) 


int powersave_nap;



#ifdef CONFIG_PPC_970_NAP

void power4_idle(void)

{

	if (!cpu_has_feature(CPU_FTR_CAN_NAP))

		return;



	if (!powersave_nap)

		return;



	if (!prep_irq_for_idle())

		return;



	if (cpu_has_feature(CPU_FTR_ALTIVEC))

		asm volatile("DSSALL ; sync" ::: "memory");



	power4_idle_nap();



	/*

	 * 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.

	 */

}

#endif



#ifdef CONFIG_SYSCTL

/*

 * Register the sysctl to set/clear powersave_nap.

arch/powerpc/kernel/idle_book3s.S

+20 −0
Original line number Diff line number Diff line
@@ -15,7 +15,9 @@ 
#include <asm/asm-offsets.h>

#include <asm/ppc-opcode.h>

#include <asm/cpuidle.h>

#include <asm/thread_info.h> /* TLF_NAPPING */



#ifdef CONFIG_PPC_P7_NAP

/*

 * Desired PSSCR in r3

 *
@@ -181,4 +183,22 @@ _GLOBAL(isa206_idle_insn_mayloss) 
	bne	2f

	IDLE_STATE_ENTER_SEQ_NORET(PPC_SLEEP)

2:	IDLE_STATE_ENTER_SEQ_NORET(PPC_WINKLE)

#endif



#ifdef CONFIG_PPC_970_NAP

_GLOBAL(power4_idle_nap)

	LOAD_REG_IMMEDIATE(r7, MSR_KERNEL|MSR_EE|MSR_POW)

	ld	r9,PACA_THREAD_INFO(r13)

	ld	r8,TI_LOCAL_FLAGS(r9)

	ori	r8,r8,_TLF_NAPPING

	std	r8,TI_LOCAL_FLAGS(r9)

	/*

	 * NAPPING bit is set, from this point onward power4_fixup_nap

	 * will cause exceptions to return to power4_idle_nap_return.

	 */

1:	sync

	isync

	mtmsrd	r7

	isync

	b	1b

#endif

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