[PATCH v2 3/4] powernv: cpuidle: Redesign idle states management

From: Shreyas B. Prabhu
Date: Tue Nov 25 2014 - 06:19:03 EST

Deep idle states like sleep and winkle are per core idle states. A core
enters these states only when all the threads enter either the
particular idle state or a deeper one. There are tasks like fastsleep
hardware bug workaround and hypervisor core state save which have to be
done only by the last thread of the core entering deep idle state and
similarly tasks like timebase resync, hypervisor core register restore
that have to be done only by the first thread waking up from these
state.

The current idle state management does not have a way to distinguish the
first/last thread of the core waking/entering idle states. Tasks like
timebase resync are done for all the threads. This is not only is
suboptimal, but can cause functionality issues when subcores and kvm is
involved.

This patch adds the necessary infrastructure to track idle states of
threads in a per-core structure. It uses this info to perform tasks like
fastsleep workaround and timebase resync only once per core.

Signed-off-by: Shreyas B. Prabhu <shreyas@xxxxxxxxxxxxxxxxxx>
Originally-by: Preeti U. Murthy <preeti@xxxxxxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
---
arch/powerpc/include/asm/cpuidle.h | 14 ++
arch/powerpc/include/asm/opal.h | 2 +
arch/powerpc/include/asm/paca.h | 4 +
arch/powerpc/kernel/asm-offsets.c | 4 +
arch/powerpc/kernel/exceptions-64s.S | 20 ++-
arch/powerpc/kernel/idle_power7.S | 186 +++++++++++++++++++------
arch/powerpc/platforms/powernv/opal-wrappers.S | 37 +++++
arch/powerpc/platforms/powernv/setup.c | 42 +++++-
arch/powerpc/platforms/powernv/smp.c | 3 +-
drivers/cpuidle/cpuidle-powernv.c | 3 +-
10 files changed, 258 insertions(+), 57 deletions(-)
create mode 100644 arch/powerpc/include/asm/cpuidle.h

diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h
new file mode 100644
index 0000000..8c82850
--- /dev/null
+++ b/arch/powerpc/include/asm/cpuidle.h
@@ -0,0 +1,14 @@
+#ifndef _ASM_POWERPC_CPUIDLE_H
+#define _ASM_POWERPC_CPUIDLE_H
+
+#ifdef CONFIG_PPC_POWERNV
+/* Used in powernv idle state management */
+#define PNV_THREAD_RUNNING 0
+#define PNV_THREAD_NAP 1
+#define PNV_THREAD_SLEEP 2
+#define PNV_THREAD_WINKLE 3
+#define PNV_CORE_IDLE_LOCK_BIT 0x100
+#define PNV_CORE_IDLE_THREAD_BITS 0x0FF
+#endif
+
+#endif
diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index f8b95c0..bef7fbc 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -152,6 +152,7 @@ struct opal_sg_list {
#define OPAL_PCI_ERR_INJECT 96
#define OPAL_PCI_EEH_FREEZE_SET 97
#define OPAL_HANDLE_HMI 98
+#define OPAL_CONFIG_CPU_IDLE_STATE 99
#define OPAL_REGISTER_DUMP_REGION 101
#define OPAL_UNREGISTER_DUMP_REGION 102

@@ -162,6 +163,7 @@ struct opal_sg_list {
*/
#define OPAL_PM_NAP_ENABLED 0x00010000
#define OPAL_PM_SLEEP_ENABLED 0x00020000
+#define OPAL_PM_SLEEP_ENABLED_ER1 0x00080000

#ifndef __ASSEMBLY__

diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index a5139ea..85aeedb 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -158,6 +158,10 @@ struct paca_struct {
* early exception handler for use by high level C handler
*/
struct opal_machine_check_event *opal_mc_evt;
+
+ /* Per-core mask tracking idle threads and a lock bit-[L][TTTTTTTT] */
+ u32 *core_idle_state_ptr;
+ u8 thread_idle_state; /* ~Idle[0]/Nap[1]/Sleep[2]/Winkle[3] */
#endif
#ifdef CONFIG_PPC_BOOK3S_64
/* Exclusive emergency stack pointer for machine check exception. */
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 9d7dede..50f299e 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -731,6 +731,10 @@ int main(void)
DEFINE(OPAL_MC_SRR0, offsetof(struct opal_machine_check_event, srr0));
DEFINE(OPAL_MC_SRR1, offsetof(struct opal_machine_check_event, srr1));
DEFINE(PACA_OPAL_MC_EVT, offsetof(struct paca_struct, opal_mc_evt));
+ DEFINE(PACA_CORE_IDLE_STATE_PTR,
+ offsetof(struct paca_struct, core_idle_state_ptr));
+ DEFINE(PACA_THREAD_IDLE_STATE,
+ offsetof(struct paca_struct, thread_idle_state));
#endif

return 0;
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 72e783e..3311c8d 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -15,6 +15,7 @@
#include <asm/hw_irq.h>
#include <asm/exception-64s.h>
#include <asm/ptrace.h>
+#include <asm/cpuidle.h>

/*
* We layout physical memory as follows:
@@ -109,15 +110,19 @@ BEGIN_FTR_SECTION
rlwinm. r13,r13,47-31,30,31
beq 9f

- /* waking up from powersave (nap) state */
cmpwi cr1,r13,2
- /* Total loss of HV state is fatal, we could try to use the
- * PIR to locate a PACA, then use an emergency stack etc...
- * OPAL v3 based powernv platforms have new idle states
- * which fall in this catagory.
- */
- bgt cr1,8f
+
GET_PACA(r13)
+ lbz r0,PACA_THREAD_IDLE_STATE(r13)
+ cmpwi cr2,r0,PNV_THREAD_NAP
+ bgt cr2,8f /* Either sleep or Winkle */
+
+ /* Waking up from nap should not cause hypervisor state loss */
+ bgt cr1,.
+
+ /* Waking up from nap */
+ li r0,PNV_THREAD_RUNNING
+ stb r0,PACA_THREAD_IDLE_STATE(r13) /* Clear thread state */

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
li r0,KVM_HWTHREAD_IN_KERNEL
@@ -1386,6 +1391,7 @@ machine_check_handle_early:
MACHINE_CHECK_HANDLER_WINDUP
GET_PACA(r13)
ld r1,PACAR1(r13)
+ li r3,PNV_THREAD_NAP
b power7_enter_nap_mode
4:
#endif
diff --git a/arch/powerpc/kernel/idle_power7.S b/arch/powerpc/kernel/idle_power7.S
index 283c603..c1d590f 100644
--- a/arch/powerpc/kernel/idle_power7.S
+++ b/arch/powerpc/kernel/idle_power7.S
@@ -18,6 +18,7 @@
#include <asm/hw_irq.h>
#include <asm/kvm_book3s_asm.h>
#include <asm/opal.h>
+#include <asm/cpuidle.h>

#undef DEBUG

@@ -37,8 +38,7 @@

/*
* Pass requested state in r3:
- * 0 - nap
- * 1 - sleep
+ * r3 - PNV_THREAD_NAP/SLEEP/WINKLE
*
* To check IRQ_HAPPENED in r4
* 0 - don't check
@@ -123,12 +123,62 @@ power7_enter_nap_mode:
li r4,KVM_HWTHREAD_IN_NAP
stb r4,HSTATE_HWTHREAD_STATE(r13)
#endif
- cmpwi cr0,r3,1
- beq 2f
+ stb r3,PACA_THREAD_IDLE_STATE(r13)
+ cmpwi cr1,r3,PNV_THREAD_SLEEP
+ bge cr1,2f
IDLE_STATE_ENTER_SEQ(PPC_NAP)
/* No return */
-2: IDLE_STATE_ENTER_SEQ(PPC_SLEEP)
- /* No return */
+2:
+ /* Sleep or winkle */
+ li r7,1
+ mfspr r8,SPRN_PIR
+ /*
+ * The last 3 bits of PIR represents the thread id of a cpu
+ * in power8. This will need adjusting for power7.
+ */
+ andi. r8,r8,0x07 /* Get thread id into r8 */
+ rotld r7,r7,r8
+
+ ld r14,PACA_CORE_IDLE_STATE_PTR(r13)
+lwarx_loop1:
+ lwarx r15,0,r14
+ andc r15,r15,r7 /* Clear thread bit */
+
+ andi. r15,r15,PNV_CORE_IDLE_THREAD_BITS
+ beq last_thread
+
+ /* Not the last thread to goto sleep */
+ stwcx. r15,0,r14
+ bne- lwarx_loop1
+ b common_enter
+
+last_thread:
+ LOAD_REG_ADDR(r3, pnv_need_fastsleep_workaround)
+ lbz r3,0(r3)
+ cmpwi r3,1
+ bne common_enter
+ /*
+ * Last thread of the core entering sleep. Last thread needs to execute
+ * the hardware bug workaround code. Before that, set the lock bit to
+ * avoid the race of other threads waking up and undoing workaround
+ * before workaround is applied.
+ */
+ ori r15,r15,PNV_CORE_IDLE_LOCK_BIT
+ stwcx. r15,0,r14
+ bne- lwarx_loop1
+
+ /* Fast sleep workaround */
+ li r3,1
+ li r4,1
+ li r0,OPAL_CONFIG_CPU_IDLE_STATE
+ bl opal_call_realmode
+
+ /* Clear Lock bit */
+ andi. r15,r15,PNV_CORE_IDLE_THREAD_BITS
+ stw r15,0(r14)
+
+common_enter: /* common code for all the threads entering sleep */
+ IDLE_STATE_ENTER_SEQ(PPC_SLEEP)

_GLOBAL(power7_idle)
/* Now check if user or arch enabled NAP mode */
@@ -141,49 +191,16 @@ _GLOBAL(power7_idle)

_GLOBAL(power7_nap)
mr r4,r3
- li r3,0
+ li r3,PNV_THREAD_NAP
b power7_powersave_common
/* No return */

_GLOBAL(power7_sleep)
- li r3,1
+ li r3,PNV_THREAD_SLEEP
li r4,1
b power7_powersave_common
/* No return */

-/*
- * Make opal call in realmode. This is a generic function to be called
- * from realmode from reset vector. It handles endianess.
- *
- * r13 - paca pointer
- * r1 - stack pointer
- * r3 - opal token
- */
-opal_call_realmode:
- mflr r12
- std r12,_LINK(r1)
- ld r2,PACATOC(r13)
- /* Set opal return address */
- LOAD_REG_ADDR(r0,return_from_opal_call)
- mtlr r0
- /* Handle endian-ness */
- li r0,MSR_LE
- mfmsr r12
- andc r12,r12,r0
- mtspr SPRN_HSRR1,r12
- mr r0,r3 /* Move opal token to r0 */
- LOAD_REG_ADDR(r11,opal)
- ld r12,8(r11)
- ld r2,0(r11)
- mtspr SPRN_HSRR0,r12
- hrfid
-
-return_from_opal_call:
- FIXUP_ENDIAN
- ld r0,_LINK(r1)
- mtlr r0
- blr
-
#define CHECK_HMI_INTERRUPT \
mfspr r0,SPRN_SRR1; \
BEGIN_FTR_SECTION_NESTED(66); \
@@ -196,10 +213,8 @@ ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 66); \
/* Invoke opal call to handle hmi */ \
ld r2,PACATOC(r13); \
ld r1,PACAR1(r13); \
- std r3,ORIG_GPR3(r1); /* Save original r3 */ \
- li r3,OPAL_HANDLE_HMI; /* Pass opal token argument*/ \
+ li r0,OPAL_HANDLE_HMI; /* Pass opal token argument*/ \
bl opal_call_realmode; \
- ld r3,ORIG_GPR3(r1); /* Restore original r3 */ \
20: nop;


@@ -210,12 +225,91 @@ _GLOBAL(power7_wakeup_tb_loss)
BEGIN_FTR_SECTION
CHECK_HMI_INTERRUPT
END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
+
+ li r7,1
+ mfspr r8,SPRN_PIR
+ /*
+ * The last 3 bits of PIR represents the thread id of a cpu
+ * in power8. This will need adjusting for power7.
+ */
+ andi. r8,r8,0x07 /* Get thread id into r8 */
+ rotld r7,r7,r8
+ /* r7 now has 'thread_id'th bit set */
+
+ ld r14,PACA_CORE_IDLE_STATE_PTR(r13)
+lwarx_loop2:
+ lwarx r15,0,r14
+ andi. r9,r15,PNV_CORE_IDLE_LOCK_BIT
+ /*
+ * Lock bit is set in one of the 2 cases-
+ * a. In the sleep/winkle enter path, the last thread is executing
+ * fastsleep workaround code.
+ * b. In the wake up path, another thread is executing fastsleep
+ * workaround undo code or resyncing timebase or restoring context
+ * In either case loop until the lock bit is cleared.
+ */
+ bne lwarx_loop2
+
+ cmpwi cr2,r15,0
+ or r15,r15,r7 /* Set thread bit */
+
+ beq cr2,first_thread
+
+ /* Not first thread in core to wake up */
+ stwcx. r15,0,r14
+ bne- lwarx_loop2
+ b common_exit
+
+first_thread:
+ /* First thread in core to wakeup */
+ ori r15,r15,PNV_CORE_IDLE_LOCK_BIT
+ stwcx. r15,0,r14
+ bne- lwarx_loop2
+
+ LOAD_REG_ADDR(r3, pnv_need_fastsleep_workaround)
+ lbz r3,0(r3)
+ cmpwi r3,1
+ /* skip fastsleep workaround if its not needed */
+ bne timebase_resync
+
+ /* Undo fast sleep workaround */
+ mfcr r16 /* Backup CR into a non-volatile register */
+ li r3,1
+ li r4,0
+ li r0,OPAL_CONFIG_CPU_IDLE_STATE
+ bl opal_call_realmode
+ mtcr r16 /* Restore CR */
+
+ /* Do timebase resync if we are waking up from sleep. Use cr1 value
+ * set in exceptions-64s.S */
+ ble cr1,clear_lock
+
+timebase_resync:
/* Time base re-sync */
- li r3,OPAL_RESYNC_TIMEBASE
+ li r0,OPAL_RESYNC_TIMEBASE
bl opal_call_realmode;
-
/* TODO: Check r3 for failure */

+clear_lock:
+ andi. r15,r15,PNV_CORE_IDLE_THREAD_BITS
+ stw r15,0(r14)
+
+common_exit:
+ li r5,PNV_THREAD_RUNNING
+ stb r5,PACA_THREAD_IDLE_STATE(r13)
+
+#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+ li r0,KVM_HWTHREAD_IN_KERNEL
+ stb r0,HSTATE_HWTHREAD_STATE(r13)
+ /* Order setting hwthread_state vs. testing hwthread_req */
+ sync
+ lbz r0,HSTATE_HWTHREAD_REQ(r13)
+ cmpwi r0,0
+ beq 6f
+ b kvm_start_guest
+6:
+#endif
+
REST_NVGPRS(r1)
REST_GPR(2, r1)
ld r3,_CCR(r1)
diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
index feb549a..b2aa93b 100644
--- a/arch/powerpc/platforms/powernv/opal-wrappers.S
+++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
@@ -158,6 +158,43 @@ opal_tracepoint_return:
blr
#endif

+/*
+ * Make opal call in realmode. This is a generic function to be called
+ * from realmode. It handles endianness.
+ *
+ * r13 - paca pointer
+ * r1 - stack pointer
+ * r0 - opal token
+ */
+_GLOBAL(opal_call_realmode)
+ mflr r12
+ std r12,_LINK(r1)
+ ld r2,PACATOC(r13)
+ /* Set opal return address */
+ LOAD_REG_ADDR(r12,return_from_opal_call)
+ mtlr r12
+
+ mfmsr r12
+#ifdef __LITTLE_ENDIAN__
+ /* Handle endian-ness */
+ li r11,MSR_LE
+ andc r12,r12,r11
+#endif
+ mtspr SPRN_HSRR1,r12
+ LOAD_REG_ADDR(r11,opal)
+ ld r12,8(r11)
+ ld r2,0(r11)
+ mtspr SPRN_HSRR0,r12
+ hrfid
+
+return_from_opal_call:
+#ifdef __LITTLE_ENDIAN__
+ FIXUP_ENDIAN
+#endif
+ ld r12,_LINK(r1)
+ mtlr r12
+ blr
+
OPAL_CALL(opal_invalid_call, OPAL_INVALID_CALL);
OPAL_CALL(opal_console_write, OPAL_CONSOLE_WRITE);
OPAL_CALL(opal_console_read, OPAL_CONSOLE_READ);
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 34c6665..17fb98c 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -36,6 +36,8 @@
#include <asm/opal.h>
#include <asm/kexec.h>
#include <asm/smp.h>
+#include <asm/cputhreads.h>
+#include <asm/cpuidle.h>

#include "powernv.h"

@@ -292,11 +294,45 @@ static void __init pnv_setup_machdep_rtas(void)

static u32 supported_cpuidle_states;

+static void pnv_alloc_idle_core_states(void)
+{
+ int i, j;
+ int nr_cores = cpu_nr_cores();
+ u32 *core_idle_state;
+
+ /*
+ * core_idle_state - First 8 bits track the idle state of each thread
+ * of the core. The 8th bit is the lock bit. Initially all thread bits
+ * are set. They are cleared when the thread enters deep idle state
+ * like sleep and winkle. Initially the lock bit is cleared.
+ * The lock bit has 2 purposes
+ * a. While the first thread is restoring core state, it prevents
+ * from other threads in the core from switching to prcoess context.
+ * b. While the last thread in the core is saving the core state, it
+ * prevent a different thread from waking up.
+ */
+ for (i = 0; i < nr_cores; i++) {
+ int first_cpu = i * threads_per_core;
+ int node = cpu_to_node(first_cpu);
+
+ core_idle_state = kmalloc_node(sizeof(u32), GFP_KERNEL, node);
+ for (j = 0; j < threads_per_core; j++) {
+ int cpu = first_cpu + j;
+
+ paca[cpu].core_idle_state_ptr = core_idle_state;
+ paca[cpu].thread_idle_state = PNV_THREAD_RUNNING;
+
+ }
+ }
+}
+
u32 pnv_get_supported_cpuidle_states(void)
{
return supported_cpuidle_states;
}
+EXPORT_SYMBOL_GPL(pnv_get_supported_cpuidle_states);

+u8 pnv_need_fastsleep_workaround;
static int __init pnv_init_idle_states(void)
{
struct device_node *power_mgt;
@@ -306,6 +342,7 @@ static int __init pnv_init_idle_states(void)
int i;

supported_cpuidle_states = 0;
+ pnv_need_fastsleep_workaround = 0;

if (cpuidle_disable != IDLE_NO_OVERRIDE)
return 0;
@@ -332,13 +369,14 @@ static int __init pnv_init_idle_states(void)
flags = be32_to_cpu(idle_state_flags[i]);
supported_cpuidle_states |= flags;
}
-
+ if (supported_cpuidle_states & OPAL_PM_SLEEP_ENABLED_ER1)
+ pnv_need_fastsleep_workaround = 1;
+ pnv_alloc_idle_core_states();
return 0;
}

subsys_initcall(pnv_init_idle_states);

-
static int __init pnv_probe(void)
{
unsigned long root = of_get_flat_dt_root();
diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index 3dc4cec..12b761a 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -167,7 +167,8 @@ static void pnv_smp_cpu_kill_self(void)
mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1);
while (!generic_check_cpu_restart(cpu)) {
ppc64_runlatch_off();
- if (idle_states & OPAL_PM_SLEEP_ENABLED)
+ if ((idle_states & OPAL_PM_SLEEP_ENABLED) ||
+ (idle_states & OPAL_PM_SLEEP_ENABLED_ER1))
power7_sleep();
else
power7_nap(1);
diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 0a7d827..a489b56 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -208,7 +208,8 @@ static int powernv_add_idle_states(void)
nr_idle_states++;
}

- if (flags & OPAL_PM_SLEEP_ENABLED) {
+ if (flags & OPAL_PM_SLEEP_ENABLED ||
+ flags & OPAL_PM_SLEEP_ENABLED_ER1) {
/* Add FASTSLEEP state */
strcpy(powernv_states[nr_idle_states].name, "FastSleep");
strcpy(powernv_states[nr_idle_states].desc, "FastSleep");
--
1.9.3

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