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

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index a9993e7a443bc501bd0aebd8e9dc82c06ac33414..e114eb36721ced145ac9b61cd79b660a0c6e7c17 100644 (file)
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -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};

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 157b0147921f14b4f337a1ade8f20f941173a88f..78a1b22d4fd836f6fcd80fcbd8d4d47987f8838d 100644 (file)
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -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

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 46508b148e1682b7587a0acb3a8ca1cbc9c99665..b049c0bfa88312fc78f263fe4488c12d6edb58c2 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -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
 

diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c
index a36fd053c3dbae785ca85cf2b5457f32bf21e9b6..422e31d2f5a2ba90257b99c756332cffa4452e7c 100644 (file)
--- a/arch/powerpc/kernel/idle.c
+++ b/arch/powerpc/kernel/idle.c
@@ -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.

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index d32751994a62c7ea8de19b3a5935637a6c9dbb2a..22f249b6f58de0bd37187b66fd70aaa039698252 100644 (file)
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -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

diff --git a/arch/powerpc/kernel/idle_power4.S b/arch/powerpc/kernel/idle_power4.S
deleted file mode 100644 (file)
index 33c6253..0000000
--- a/arch/powerpc/kernel/idle_power4.S
+++ /dev/null
@@ -1,83 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-/*
- *  This file contains the power_save function for 970-family CPUs.
- */
-
-#include <linux/threads.h>
-#include <asm/processor.h>
-#include <asm/page.h>
-#include <asm/cputable.h>
-#include <asm/thread_info.h>
-#include <asm/ppc_asm.h>
-#include <asm/asm-offsets.h>
-#include <asm/irqflags.h>
-#include <asm/hw_irq.h>
-#include <asm/feature-fixups.h>
-
-#undef DEBUG
-
-       .text
-
-_GLOBAL(power4_idle)
-BEGIN_FTR_SECTION
-       blr
-END_FTR_SECTION_IFCLR(CPU_FTR_CAN_NAP)
-       /* Now check if user or arch enabled NAP mode */
-       LOAD_REG_ADDRBASE(r3,powersave_nap)
-       lwz     r4,ADDROFF(powersave_nap)(r3)
-       cmpwi   0,r4,0
-       beqlr
-
-       /* This sequence is similar to prep_irq_for_idle() */
-
-       /* Hard disable interrupts */
-       mfmsr   r7
-       rldicl  r0,r7,48,1
-       rotldi  r0,r0,16
-       mtmsrd  r0,1
-
-       /* Check if something happened while soft-disabled */
-       lbz     r0,PACAIRQHAPPENED(r13)
-       cmpwi   cr0,r0,0
-       bne-    2f
-
-       /*
-        * Soft-enable interrupts. This will make power4_fixup_nap return
-        * to our caller with interrupts enabled (soft and hard). The caller
-        * can cope with either interrupts disabled or enabled upon return.
-        */
-#ifdef CONFIG_TRACE_IRQFLAGS
-       /* Tell the tracer interrupts are on, because idle responds to them. */
-       mflr    r0
-       std     r0,16(r1)
-       stdu    r1,-128(r1)
-       bl      trace_hardirqs_on
-       addi    r1,r1,128
-       ld      r0,16(r1)
-       mtlr    r0
-       mfmsr   r7
-#endif /* CONFIG_TRACE_IRQFLAGS */
-
-       li      r0,IRQS_ENABLED
-       stb     r0,PACAIRQSOFTMASK(r13) /* we'll hard-enable shortly */
-BEGIN_FTR_SECTION
-       DSSALL
-       sync
-END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
-       ld      r9, PACA_THREAD_INFO(r13)
-       ld      r8,TI_LOCAL_FLAGS(r9)   /* set napping bit */
-       ori     r8,r8,_TLF_NAPPING      /* so when we take an exception */
-       std     r8,TI_LOCAL_FLAGS(r9)   /* it will return to our caller */
-       ori     r7,r7,MSR_EE
-       oris    r7,r7,MSR_POW@h
-1:     sync
-       isync
-       mtmsrd  r7
-       isync
-       b       1b
-
-2:     /* Return if an interrupt had happened while soft disabled */
-       /* Set the HARD_DIS flag because interrupts are now hard disabled */
-       ori     r0,r0,PACA_IRQ_HARD_DIS
-       stb     r0,PACAIRQHAPPENED(r13)
-       blr

diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index e28df298df5635aacedf99630c811473d0ef8614..1f8025383caa2596ccd8d5d1378a2ec5b482f4ec 100644 (file)
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -177,6 +177,10 @@ config PPC_970_NAP
 config PPC_P7_NAP
        bool
 
+config PPC_BOOK3S_IDLE
+       def_bool y
+       depends on (PPC_970_NAP || PPC_P7_NAP)
+
 config PPC_INDIRECT_PIO
        bool
        select GENERIC_IOMAP