[PATCH v3 0/3] powernv:stop: Use psscr_val,mask provided by firmware

[PATCH v3 0/3] powernv:stop: Use psscr_val,mask provided by firmware

[Gautham R. Shenoy]

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

This is the third iteration of the patchset to use the psscr_val and
psscr_mask provided by the firmware for each of the stop states.

The previous version can be found here:

[v2]: https://lkml.org/lkml/2016/10/27/143
[v1]: https://lkml.org/lkml/2016/9/29/45

This version fixes a couple of bugs pertaining to strncpy and
initialization of the target-residency values of nap and sleep
which were pointed out by Paul and Oliver in the earlier version.

Synopsis
==========
In the current implementation, the code for ISA
v3.0 stop implementation has a couple of shortcomings.

a) The code hand-codes the values for ESL,EC,TR,MTL bits of PSSCR and
   uses only the RL field from the firmware. While this is not
   incorrect, since the hand-coded values are legitimate, it is not a
   very flexible design since the firmware has the capability to
   communicate these values via the "ibm,cpu-idle-state-psscr" and
   "ibm,cpu-idle-state-psscr-mask" properties. In case where the
   firmware provides values for these fields that is different from
   the hand-coded values, the current code will not work as intended.

b) Due to issue a), the current code assumes that ESL=EC=1 for all the
   stop states and hence the wakeup from the stop instruction will
   happen at 0x100, the system-reset vector. However, the ISA v3.0
   allows the ESL=EC=0 behaviour where the corresponding stop-state
   loses no state and wakes up from the subsequent instruction. The
   current code doesn't handle this case.
   
This patch series addresses these issues.

The first patch in the series renames the existing
IDLE_STATE_ENTER_SEQ macro to IDLE_STATE_ENTER_SEQ_NORET. It reuses
the name IDLE_STATE_ENTER_SEQ for entering into stop-states which wake
up at the subsequent instruction.

The second patch adds a helper function in cpuidle-powernv.c for
initializing entries of the powernv_states[] table that is passed to
the cpu-idle core. This eliminates some of the code duplication in the
function that discovers and initializes the stop states.

The third patch in the series fixes issues a) and b) by ensuring that
the psscr-value and the psscr-mask provided by the firmware are what
will be used to set a particular stop state. It also adds support for
handling wake-up from stop states which were entered with ESL=EC=0.

The third patch also handles the older firmware which sets only the
Requested Level (RL) field in the psscr and psscr-mask exposed in the
device tree. In the presence of such older firmware, this patch will
set the default sane values for for remaining PSSCR fields (i.e PSLL,
MTL, ESL, EC, and TR).

The skiboot patch populates all the relevant fields in the PSSCR
values and the mask for all the stop states can be found here:
https://lists.ozlabs.org/pipermail/skiboot/2016-September/004869.html

The patches are based on top of
git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git fixes

Gautham R. Shenoy (3):
  powernv:idle: Add IDLE_STATE_ENTER_SEQ_NORET macro
  cpuidle:powernv: Add helper function to populate powernv idle states.
  powernv: Pass PSSCR value and mask to power9_idle_stop

 arch/powerpc/include/asm/cpuidle.h       |  42 +++++++++++-
 arch/powerpc/include/asm/processor.h     |   3 +-
 arch/powerpc/kernel/exceptions-64s.S     |   6 +-
 arch/powerpc/kernel/idle_book3s.S        |  41 +++++++-----
 arch/powerpc/platforms/powernv/idle.c    |  81 ++++++++++++++++++----
 arch/powerpc/platforms/powernv/powernv.h |   3 +-
 arch/powerpc/platforms/powernv/smp.c     |  14 ++--
 drivers/cpuidle/cpuidle-powernv.c        | 111 +++++++++++++++++++------------
 include/linux/cpuidle.h                  |   1 +
 9 files changed, 219 insertions(+), 83 deletions(-)

-- 
1.9.4

[PATCH v3 1/3] powernv:idle: Add IDLE_STATE_ENTER_SEQ_NORET macro

[Gautham R. Shenoy]

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

Currently all the low-power idle states are expected to wake up
at reset vector 0x100. Which is why the macro IDLE_STATE_ENTER_SEQ
that puts the CPU to an idle state and never returns.

On ISA_300, when the ESL and EC bits in the PSSCR are zero, the
CPU is expected to wake up at the next instruction of the idle
instruction.

This patch adds a new macro named IDLE_STATE_ENTER_SEQ_NORET for the
no-return variant and reuses the name IDLE_STATE_ENTER_SEQ
for a variant that allows resuming operation at the instruction next
to the idle-instruction.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/cpuidle.h   |  5 ++++-
 arch/powerpc/kernel/exceptions-64s.S |  6 +++---
 arch/powerpc/kernel/idle_book3s.S    | 10 +++++-----
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h
index 3919332..0a3255b 100644
--- a/arch/powerpc/include/asm/cpuidle.h
+++ b/arch/powerpc/include/asm/cpuidle.h
@@ -21,7 +21,7 @@
 
 /* Idle state entry routines */
 #ifdef	CONFIG_PPC_P7_NAP
-#define	IDLE_STATE_ENTER_SEQ(IDLE_INST)				\
+#define IDLE_STATE_ENTER_SEQ(IDLE_INST)                         \
 	/* Magic NAP/SLEEP/WINKLE mode enter sequence */	\
 	std	r0,0(r1);					\
 	ptesync;						\
@@ -29,6 +29,9 @@
 1:	cmpd	cr0,r0,r0;					\
 	bne	1b;						\
 	IDLE_INST;						\
+
+#define	IDLE_STATE_ENTER_SEQ_NORET(IDLE_INST)			\
+	IDLE_STATE_ENTER_SEQ(IDLE_INST)                         \
 	b	.
 #endif /* CONFIG_PPC_P7_NAP */
 
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 1ba82ea..7aa8afc 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -381,12 +381,12 @@ EXC_COMMON_BEGIN(machine_check_handle_early)
 	lbz	r3,PACA_THREAD_IDLE_STATE(r13)
 	cmpwi	r3,PNV_THREAD_NAP
 	bgt	10f
-	IDLE_STATE_ENTER_SEQ(PPC_NAP)
+	IDLE_STATE_ENTER_SEQ_NORET(PPC_NAP)
 	/* No return */
 10:
 	cmpwi	r3,PNV_THREAD_SLEEP
 	bgt	2f
-	IDLE_STATE_ENTER_SEQ(PPC_SLEEP)
+	IDLE_STATE_ENTER_SEQ_NORET(PPC_SLEEP)
 	/* No return */
 
 2:
@@ -400,7 +400,7 @@ EXC_COMMON_BEGIN(machine_check_handle_early)
 	 */
 	ori	r13,r13,1
 	SET_PACA(r13)
-	IDLE_STATE_ENTER_SEQ(PPC_WINKLE)
+	IDLE_STATE_ENTER_SEQ_NORET(PPC_WINKLE)
 	/* No return */
 4:
 #endif
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 72dac0b..be90e2f 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -205,7 +205,7 @@ pnv_enter_arch207_idle_mode:
 	stb	r3,PACA_THREAD_IDLE_STATE(r13)
 	cmpwi	cr3,r3,PNV_THREAD_SLEEP
 	bge	cr3,2f
-	IDLE_STATE_ENTER_SEQ(PPC_NAP)
+	IDLE_STATE_ENTER_SEQ_NORET(PPC_NAP)
 	/* No return */
 2:
 	/* Sleep or winkle */
@@ -239,7 +239,7 @@ pnv_fastsleep_workaround_at_entry:
 
 common_enter: /* common code for all the threads entering sleep or winkle */
 	bgt	cr3,enter_winkle
-	IDLE_STATE_ENTER_SEQ(PPC_SLEEP)
+	IDLE_STATE_ENTER_SEQ_NORET(PPC_SLEEP)
 
 fastsleep_workaround_at_entry:
 	ori	r15,r15,PNV_CORE_IDLE_LOCK_BIT
@@ -261,7 +261,7 @@ fastsleep_workaround_at_entry:
 enter_winkle:
 	bl	save_sprs_to_stack
 
-	IDLE_STATE_ENTER_SEQ(PPC_WINKLE)
+	IDLE_STATE_ENTER_SEQ_NORET(PPC_WINKLE)
 
 /*
  * r3 - requested stop state
@@ -280,7 +280,7 @@ power_enter_stop:
 	ld	r4,ADDROFF(pnv_first_deep_stop_state)(r5)
 	cmpd	r3,r4
 	bge	2f
-	IDLE_STATE_ENTER_SEQ(PPC_STOP)
+	IDLE_STATE_ENTER_SEQ_NORET(PPC_STOP)
 2:
 /*
  * Entering deep idle state.
@@ -302,7 +302,7 @@ lwarx_loop_stop:
 
 	bl	save_sprs_to_stack
 
-	IDLE_STATE_ENTER_SEQ(PPC_STOP)
+	IDLE_STATE_ENTER_SEQ_NORET(PPC_STOP)
 
 _GLOBAL(power7_idle)
 	/* Now check if user or arch enabled NAP mode */
-- 
1.9.4

[PATCH v3 2/3] cpuidle:powernv: Add helper function to populate powernv idle states.

[Gautham R. Shenoy]

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

In the current code for powernv_add_idle_states, there is a lot of code
duplication while initializing an idle state in powernv_states table.

Add an inline helper function to populate the powernv_states[] table for
a given idle state. Invoke this for populating the "Nap", "Fastsleep"
and the stop states in powernv_add_idle_states.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
 drivers/cpuidle/cpuidle-powernv.c | 83 ++++++++++++++++++++++-----------------
 include/linux/cpuidle.h           |  1 +
 2 files changed, 48 insertions(+), 36 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 7fe442c..9240e08 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -167,6 +167,24 @@ static int powernv_cpuidle_driver_init(void)
 	return 0;
 }
 
+static inline void add_powernv_state(int index, const char *name,
+				     unsigned int flags,
+				     int (*idle_fn)(struct cpuidle_device *,
+						    struct cpuidle_driver *,
+						    int),
+				     unsigned int target_residency,
+				     unsigned int exit_latency,
+				     u64 psscr_val)
+{
+	strlcpy(powernv_states[index].name, name, CPUIDLE_NAME_LEN);
+	strlcpy(powernv_states[index].desc, name, CPUIDLE_NAME_LEN);
+	powernv_states[index].flags = flags;
+	powernv_states[index].target_residency = target_residency;
+	powernv_states[index].exit_latency = exit_latency;
+	powernv_states[index].enter = idle_fn;
+	stop_psscr_table[index] = psscr_val;
+}
+
 static int powernv_add_idle_states(void)
 {
 	struct device_node *power_mgt;
@@ -236,6 +254,7 @@ static int powernv_add_idle_states(void)
 		"ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);
 
 	for (i = 0; i < dt_idle_states; i++) {
+		unsigned int exit_latency, target_residency;
 		/*
 		 * If an idle state has exit latency beyond
 		 * POWERNV_THRESHOLD_LATENCY_NS then don't use it
@@ -243,28 +262,31 @@ static int powernv_add_idle_states(void)
 		 */
 		if (latency_ns[i] > POWERNV_THRESHOLD_LATENCY_NS)
 			continue;
+		/*
+		 * Firmware passes residency and latency values in ns.
+		 * cpuidle expects it in us.
+		 */
+		exit_latency = ((unsigned int)latency_ns[i]) / 1000;
+		target_residency = (!rc) ? ((unsigned int)residency_ns[i]) : 0;
+		target_residency /= 1000;
 
 		/*
-		 * Cpuidle accepts exit_latency and target_residency in us.
-		 * Use default target_residency values if f/w does not expose it.
+		 * For nap and fastsleep, use default target_residency
+		 * values if f/w does not expose it.
 		 */
 		if (flags[i] & OPAL_PM_NAP_ENABLED) {
+			if (!rc)
+				target_residency = 100;
 			/* Add NAP state */
-			strcpy(powernv_states[nr_idle_states].name, "Nap");
-			strcpy(powernv_states[nr_idle_states].desc, "Nap");
-			powernv_states[nr_idle_states].flags = 0;
-			powernv_states[nr_idle_states].target_residency = 100;
-			powernv_states[nr_idle_states].enter = nap_loop;
+			add_powernv_state(nr_idle_states, "Nap",
+					  CPUIDLE_FLAG_NONE, nap_loop,
+					  target_residency, exit_latency, 0);
 		} else if ((flags[i] & OPAL_PM_STOP_INST_FAST) &&
 				!(flags[i] & OPAL_PM_TIMEBASE_STOP)) {
-			strncpy(powernv_states[nr_idle_states].name,
-				names[i], CPUIDLE_NAME_LEN);
-			strncpy(powernv_states[nr_idle_states].desc,
-				names[i], CPUIDLE_NAME_LEN);
-			powernv_states[nr_idle_states].flags = 0;
-
-			powernv_states[nr_idle_states].enter = stop_loop;
-			stop_psscr_table[nr_idle_states] = psscr_val[i];
+			add_powernv_state(nr_idle_states, names[i],
+					  CPUIDLE_FLAG_NONE, stop_loop,
+					  target_residency, exit_latency,
+					  psscr_val[i]);
 		}
 
 		/*
@@ -274,32 +296,21 @@ static int powernv_add_idle_states(void)
 #ifdef CONFIG_TICK_ONESHOT
 		if (flags[i] & OPAL_PM_SLEEP_ENABLED ||
 			flags[i] & OPAL_PM_SLEEP_ENABLED_ER1) {
+			if (!rc)
+				target_residency = 300000;
 			/* Add FASTSLEEP state */
-			strcpy(powernv_states[nr_idle_states].name, "FastSleep");
-			strcpy(powernv_states[nr_idle_states].desc, "FastSleep");
-			powernv_states[nr_idle_states].flags = CPUIDLE_FLAG_TIMER_STOP;
-			powernv_states[nr_idle_states].target_residency = 300000;
-			powernv_states[nr_idle_states].enter = fastsleep_loop;
+			add_powernv_state(nr_idle_states, "FastSleep",
+					  CPUIDLE_FLAG_TIMER_STOP,
+					  fastsleep_loop,
+					  target_residency, exit_latency, 0);
 		} else if ((flags[i] & OPAL_PM_STOP_INST_DEEP) &&
 				(flags[i] & OPAL_PM_TIMEBASE_STOP)) {
-			strncpy(powernv_states[nr_idle_states].name,
-				names[i], CPUIDLE_NAME_LEN);
-			strncpy(powernv_states[nr_idle_states].desc,
-				names[i], CPUIDLE_NAME_LEN);
-
-			powernv_states[nr_idle_states].flags = CPUIDLE_FLAG_TIMER_STOP;
-			powernv_states[nr_idle_states].enter = stop_loop;
-			stop_psscr_table[nr_idle_states] = psscr_val[i];
+			add_powernv_state(nr_idle_states, names[i],
+					  CPUIDLE_FLAG_TIMER_STOP, stop_loop,
+					  target_residency, exit_latency,
+					  psscr_val[i]);
 		}
 #endif
-		powernv_states[nr_idle_states].exit_latency =
-				((unsigned int)latency_ns[i]) / 1000;
-
-		if (!rc) {
-			powernv_states[nr_idle_states].target_residency =
-				((unsigned int)residency_ns[i]) / 1000;
-		}
-
 		nr_idle_states++;
 	}
 out:
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index bb31373..c4e10f8 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -62,6 +62,7 @@ struct cpuidle_state {
 };
 
 /* Idle State Flags */
+#define CPUIDLE_FLAG_NONE       (0x00)
 #define CPUIDLE_FLAG_COUPLED	(0x02) /* state applies to multiple cpus */
 #define CPUIDLE_FLAG_TIMER_STOP (0x04)  /* timer is stopped on this state */
 
-- 
1.9.4

[PATCH v3 3/3] powernv: Pass PSSCR value and mask to power9_idle_stop

[Gautham R. Shenoy]

From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

The power9_idle_stop method currently takes only the requested stop
level as a parameter and picks up the rest of the PSSCR bits from a
hand-coded macro. This is not a very flexible design, especially when
the firmware has the capability to communicate the psscr value and the
mask associated with a particular stop state via device tree.

This patch modifies the power9_idle_stop API to take as parameters the
PSSCR value and the PSSCR mask corresponding to the stop state that
needs to be set. These PSSCR value and mask are respectively obtained
by parsing the "ibm,cpu-idle-state-psscr" and
"ibm,cpu-idle-state-psscr-mask" fields from the device tree.

In addition to this, the patch adds support for handling stop states
for which ESL and EC bits in the PSSCR are zero. As per the
architecture, a wakeup from these stop states resumes execution from
the subsequent instruction as opposed to waking up at the System
Vector.

The older firmware sets only the Requested Level (RL) field in the
psscr and psscr-mask exposed in the device tree. For older firmware
where psscr-mask=0xf, this patch will set the default sane values that
the set for for remaining PSSCR fields (i.e PSLL, MTL, ESL, EC, and
TR).

This skiboot patch that exports fully populated PSSCR values and the
mask for all the stop states can be found here:
https://lists.ozlabs.org/pipermail/skiboot/2016-September/004869.html

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/cpuidle.h       | 37 +++++++++++++++
 arch/powerpc/include/asm/processor.h     |  3 +-
 arch/powerpc/kernel/idle_book3s.S        | 31 +++++++-----
 arch/powerpc/platforms/powernv/idle.c    | 81 ++++++++++++++++++++++++++------
 arch/powerpc/platforms/powernv/powernv.h |  3 +-
 arch/powerpc/platforms/powernv/smp.c     | 14 +++---
 drivers/cpuidle/cpuidle-powernv.c        | 40 +++++++++++-----
 7 files changed, 165 insertions(+), 44 deletions(-)

diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h
index 0a3255b..41b5d27 100644
--- a/arch/powerpc/include/asm/cpuidle.h
+++ b/arch/powerpc/include/asm/cpuidle.h
@@ -10,11 +10,48 @@
 #define PNV_CORE_IDLE_LOCK_BIT          0x100
 #define PNV_CORE_IDLE_THREAD_BITS       0x0FF
 
+/*
+ * By default we set the ESL and EC bits in the PSSCR.
+ *
+ * The MTL and PSLL are set to the maximum value possible as per the
+ * ISA, i.e 15.
+ *
+ * The Transition Rate is set to the Maximum value 3.
+ */
+#define PSSCR_HV_DEFAULT_VAL    (PSSCR_ESL | PSSCR_EC |		    \
+				PSSCR_PSLL_MASK | PSSCR_TR_MASK |   \
+				PSSCR_MTL_MASK)
+
+#define PSSCR_HV_DEFAULT_MASK   (PSSCR_ESL | PSSCR_EC |		    \
+				PSSCR_PSLL_MASK | PSSCR_TR_MASK |   \
+				PSSCR_MTL_MASK | PSSCR_RL_MASK)
+
 #ifndef __ASSEMBLY__
 extern u32 pnv_fastsleep_workaround_at_entry[];
 extern u32 pnv_fastsleep_workaround_at_exit[];
 
 extern u64 pnv_first_deep_stop_state;
+
+/*
+ * Older firmware only populates the RL field in psscr_val and
+ * psscr_mask.
+ *
+ * Set the remaining fields to the default value in case of the
+ * older firmware.
+ */
+static inline u64 compute_psscr_val(u64 psscr_val, u64 psscr_mask)
+{
+	if (psscr_mask == 0xf)
+		return psscr_val | PSSCR_HV_DEFAULT_VAL;
+	return psscr_val;
+}
+
+static inline u64 compute_psscr_mask(u64 psscr_mask)
+{
+	if (psscr_mask == 0xf)
+		return PSSCR_HV_DEFAULT_MASK;
+	return psscr_mask;
+}
 #endif
 
 #endif
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index c07c31b..422becd 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -458,7 +458,8 @@ static inline unsigned long get_clean_sp(unsigned long sp, int is_32)
 extern unsigned long power7_nap(int check_irq);
 extern unsigned long power7_sleep(void);
 extern unsigned long power7_winkle(void);
-extern unsigned long power9_idle_stop(unsigned long stop_level);
+extern unsigned long power9_idle_stop(unsigned long stop_psscr_val,
+				      unsigned long stop_psscr_mask);
 
 extern void flush_instruction_cache(void);
 extern void hard_reset_now(void);
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index be90e2f..37ee533 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -40,9 +40,7 @@
 #define _WORC	GPR11
 #define _PTCR	GPR12
 
-#define PSSCR_HV_TEMPLATE	PSSCR_ESL | PSSCR_EC | \
-				PSSCR_PSLL_MASK | PSSCR_TR_MASK | \
-				PSSCR_MTL_MASK
+#define PSSCR_EC_ESL_MASK_SHIFTED          (PSSCR_EC | PSSCR_ESL) >> 16
 
 	.text
 
@@ -264,7 +262,7 @@ enter_winkle:
 	IDLE_STATE_ENTER_SEQ_NORET(PPC_WINKLE)
 
 /*
- * r3 - requested stop state
+ * r3 - PSSCR value corresponding to the requested stop state.
  */
 power_enter_stop:
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
@@ -274,9 +272,19 @@ power_enter_stop:
 	stb	r4,HSTATE_HWTHREAD_STATE(r13)
 #endif
 /*
+ * Check if we are executing the lite variant with ESL=EC=0
+ */
+	andis.   r4, r3, PSSCR_EC_ESL_MASK_SHIFTED
+	andi.    r3, r3, PSSCR_RL_MASK   /* r3 = requested stop state */
+	cmpdi	 r4, 0
+	bne	 1f
+	IDLE_STATE_ENTER_SEQ(PPC_STOP)
+	li	r3,0  /* Since we didn't lose state, return 0 */
+	b 	pnv_wakeup_noloss
+/*
  * Check if the requested state is a deep idle state.
  */
-	LOAD_REG_ADDRBASE(r5,pnv_first_deep_stop_state)
+1:	LOAD_REG_ADDRBASE(r5,pnv_first_deep_stop_state)
 	ld	r4,ADDROFF(pnv_first_deep_stop_state)(r5)
 	cmpd	r3,r4
 	bge	2f
@@ -353,16 +361,17 @@ ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 66);		\
 	ld	r3,ORIG_GPR3(r1);	/* Restore original r3 */	\
 20:	nop;
 
-
 /*
- * r3 - requested stop state
+ * r3 - The PSSCR value corresponding to the stop state.
+ * r4 - The PSSCR mask corrresonding to the stop state.
  */
 _GLOBAL(power9_idle_stop)
-	LOAD_REG_IMMEDIATE(r4, PSSCR_HV_TEMPLATE)
-	or	r4,r4,r3
-	mtspr	SPRN_PSSCR, r4
-	li	r4, 1
+	mfspr   r5, SPRN_PSSCR
+	andc    r5, r5, r4
+	or      r3, r3, r5
+	mtspr 	SPRN_PSSCR, r3
 	LOAD_REG_ADDR(r5,power_enter_stop)
+	li	r4, 1
 	b	pnv_powersave_common
 	/* No return */
 /*
diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 479c256..663c6ef 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -237,15 +237,21 @@ static DEVICE_ATTR(fastsleep_workaround_applyonce, 0600,
 			show_fastsleep_workaround_applyonce,
 			store_fastsleep_workaround_applyonce);
 
+/*
+ * The default stop state that will be used by ppc_md.power_save
+ * function on platforms that support stop instruction.
+ */
+u64 pnv_default_stop_val;
+u64 pnv_default_stop_mask;
 
 /*
  * Used for ppc_md.power_save which needs a function with no parameters
  */
 static void power9_idle(void)
 {
-	/* Requesting stop state 0 */
-	power9_idle_stop(0);
+	power9_idle_stop(pnv_default_stop_val, pnv_default_stop_mask);
 }
+
 /*
  * First deep stop state. Used to figure out when to save/restore
  * hypervisor context.
@@ -253,9 +259,11 @@ static void power9_idle(void)
 u64 pnv_first_deep_stop_state = MAX_STOP_STATE;
 
 /*
- * Deepest stop idle state. Used when a cpu is offlined
+ * psscr value and mask of the deepest stop idle state.
+ * Used when a cpu is offlined.
  */
-u64 pnv_deepest_stop_state;
+u64 pnv_deepest_stop_psscr_val;
+u64 pnv_deepest_stop_psscr_mask;
 
 /*
  * Power ISA 3.0 idle initialization.
@@ -302,28 +310,58 @@ static int __init pnv_arch300_idle_init(struct device_node *np, u32 *flags,
 					int dt_idle_states)
 {
 	u64 *psscr_val = NULL;
+	u64 *psscr_mask = NULL;
+	u32 *residency_ns = NULL;
+	u64 max_residency_ns = 0;
 	int rc = 0, i;
+	bool default_stop_found = false;
 
-	psscr_val = kcalloc(dt_idle_states, sizeof(*psscr_val),
-				GFP_KERNEL);
-	if (!psscr_val) {
+	psscr_val = kcalloc(dt_idle_states, sizeof(*psscr_val), GFP_KERNEL);
+	psscr_mask = kcalloc(dt_idle_states, sizeof(*psscr_mask), GFP_KERNEL);
+	residency_ns = kcalloc(dt_idle_states, sizeof(*residency_ns),
+			       GFP_KERNEL);
+
+	if (!psscr_val || !psscr_mask || !residency_ns) {
 		rc = -1;
 		goto out;
 	}
+
 	if (of_property_read_u64_array(np,
 		"ibm,cpu-idle-state-psscr",
 		psscr_val, dt_idle_states)) {
-		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-states-psscr in DT\n");
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-psscr in DT\n");
+		rc = -1;
+		goto out;
+	}
+
+	if (of_property_read_u64_array(np,
+				       "ibm,cpu-idle-state-psscr-mask",
+				       psscr_mask, dt_idle_states)) {
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-psscr-mask in DT\n");
+		rc = -1;
+		goto out;
+	}
+
+	if (of_property_read_u32_array(np,
+				       "ibm,cpu-idle-state-residency-ns",
+					residency_ns, dt_idle_states)) {
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-residency-ns in DT\n");
 		rc = -1;
 		goto out;
 	}
 
 	/*
-	 * Set pnv_first_deep_stop_state and pnv_deepest_stop_state.
+	 * Set pnv_first_deep_stop_state, pnv_deepest_stop_psscr_{val,mask},
+	 * and the pnv_default_stop_{val,mask}.
+	 *
 	 * pnv_first_deep_stop_state should be set to the first stop
 	 * level to cause hypervisor state loss.
-	 * pnv_deepest_stop_state should be set to the deepest stop
-	 * stop state.
+	 *
+	 * pnv_deepest_stop_{val,mask} should be set to values corresponding to
+	 * the deepest stop state.
+	 *
+	 * pnv_default_stop_{val,mask} should be set to values corresponding to
+	 * the shallowest (OPAL_PM_STOP_INST_FAST) loss-less stop state.
 	 */
 	pnv_first_deep_stop_state = MAX_STOP_STATE;
 	for (i = 0; i < dt_idle_states; i++) {
@@ -333,12 +371,27 @@ static int __init pnv_arch300_idle_init(struct device_node *np, u32 *flags,
 		     (pnv_first_deep_stop_state > psscr_rl))
 			pnv_first_deep_stop_state = psscr_rl;
 
-		if (pnv_deepest_stop_state < psscr_rl)
-			pnv_deepest_stop_state = psscr_rl;
-	}
+		if (max_residency_ns < residency_ns[i]) {
+			max_residency_ns = residency_ns[i];
+			pnv_deepest_stop_psscr_val =
+				compute_psscr_val(psscr_val[i], psscr_mask[i]);
+			pnv_deepest_stop_psscr_mask =
+				compute_psscr_mask(psscr_mask[i]);
+		}
 
+		if (!default_stop_found &&
+		    (flags[i] & OPAL_PM_STOP_INST_FAST)) {
+			pnv_default_stop_val =
+				compute_psscr_val(psscr_val[i], psscr_mask[i]);
+			pnv_default_stop_mask =
+				compute_psscr_mask(psscr_mask[i]);
+			default_stop_found = true;
+		}
+	}
 out:
 	kfree(psscr_val);
+	kfree(psscr_mask);
+	kfree(residency_ns);
 	return rc;
 }
 
diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
index da7c843..6130522 100644
--- a/arch/powerpc/platforms/powernv/powernv.h
+++ b/arch/powerpc/platforms/powernv/powernv.h
@@ -18,7 +18,8 @@ static inline void pnv_pci_shutdown(void) { }
 #endif
 
 extern u32 pnv_get_supported_cpuidle_states(void);
-extern u64 pnv_deepest_stop_state;
+extern u64 pnv_deepest_stop_psscr_val;
+extern u64 pnv_deepest_stop_psscr_mask;
 
 extern void pnv_lpc_init(void);
 
diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index c789258..1c6405f 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c
@@ -182,15 +182,17 @@ static void pnv_smp_cpu_kill_self(void)
 
 		ppc64_runlatch_off();
 
-		if (cpu_has_feature(CPU_FTR_ARCH_300))
-			srr1 = power9_idle_stop(pnv_deepest_stop_state);
-		else if (idle_states & OPAL_PM_WINKLE_ENABLED)
+		if (cpu_has_feature(CPU_FTR_ARCH_300)) {
+			srr1 = power9_idle_stop(pnv_deepest_stop_psscr_val,
+						pnv_deepest_stop_psscr_mask);
+		} else if (idle_states & OPAL_PM_WINKLE_ENABLED) {
 			srr1 = power7_winkle();
-		else if ((idle_states & OPAL_PM_SLEEP_ENABLED) ||
-				(idle_states & OPAL_PM_SLEEP_ENABLED_ER1))
+		} else if ((idle_states & OPAL_PM_SLEEP_ENABLED) ||
+			   (idle_states & OPAL_PM_SLEEP_ENABLED_ER1)) {
 			srr1 = power7_sleep();
-		else
+		} else {
 			srr1 = power7_nap(1);
+		}
 
 		ppc64_runlatch_on();
 
diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 9240e08..57f84a1 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -19,6 +19,7 @@
 #include <asm/firmware.h>
 #include <asm/opal.h>
 #include <asm/runlatch.h>
+#include <asm/cpuidle.h>
 
 #define POWERNV_THRESHOLD_LATENCY_NS 200000
 
@@ -30,7 +31,12 @@ struct cpuidle_driver powernv_idle_driver = {
 static int max_idle_state;
 static struct cpuidle_state *cpuidle_state_table;
 
-static u64 stop_psscr_table[CPUIDLE_STATE_MAX];
+struct stop_psscr_table {
+	u64 val;
+	u64 mask;
+};
+
+static struct stop_psscr_table stop_psscr_table[CPUIDLE_STATE_MAX];
 
 static u64 snooze_timeout;
 static bool snooze_timeout_en;
@@ -102,7 +108,8 @@ static int stop_loop(struct cpuidle_device *dev,
 		     int index)
 {
 	ppc64_runlatch_off();
-	power9_idle_stop(stop_psscr_table[index]);
+	power9_idle_stop(stop_psscr_table[index].val,
+			 stop_psscr_table[index].mask);
 	ppc64_runlatch_on();
 	return index;
 }
@@ -174,7 +181,7 @@ static inline void add_powernv_state(int index, const char *name,
 						    int),
 				     unsigned int target_residency,
 				     unsigned int exit_latency,
-				     u64 psscr_val)
+				     u64 psscr_val, u64 psscr_mask)
 {
 	strlcpy(powernv_states[index].name, name, CPUIDLE_NAME_LEN);
 	strlcpy(powernv_states[index].desc, name, CPUIDLE_NAME_LEN);
@@ -182,7 +189,9 @@ static inline void add_powernv_state(int index, const char *name,
 	powernv_states[index].target_residency = target_residency;
 	powernv_states[index].exit_latency = exit_latency;
 	powernv_states[index].enter = idle_fn;
-	stop_psscr_table[index] = psscr_val;
+	stop_psscr_table[index].val = compute_psscr_val(psscr_val,
+							psscr_mask);
+	stop_psscr_table[index].mask = compute_psscr_mask(psscr_mask);
 }
 
 static int powernv_add_idle_states(void)
@@ -194,6 +203,7 @@ static int powernv_add_idle_states(void)
 	u32 residency_ns[CPUIDLE_STATE_MAX];
 	u32 flags[CPUIDLE_STATE_MAX];
 	u64 psscr_val[CPUIDLE_STATE_MAX];
+	u64 psscr_mask[CPUIDLE_STATE_MAX];
 	const char *names[CPUIDLE_STATE_MAX];
 	int i, rc;
 
@@ -241,15 +251,23 @@ static int powernv_add_idle_states(void)
 
 	/*
 	 * If the idle states use stop instruction, probe for psscr values
-	 * which are necessary to specify required stop level.
+	 * and psscr mask which are necessary to specify required stop level.
 	 */
-	if (flags[0] & (OPAL_PM_STOP_INST_FAST | OPAL_PM_STOP_INST_DEEP))
+	if (flags[0] & (OPAL_PM_STOP_INST_FAST | OPAL_PM_STOP_INST_DEEP)) {
 		if (of_property_read_u64_array(power_mgt,
 		    "ibm,cpu-idle-state-psscr", psscr_val, dt_idle_states)) {
-			pr_warn("cpuidle-powernv: missing ibm,cpu-idle-states-psscr in DT\n");
+			pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-psscr in DT\n");
 			goto out;
 		}
 
+		if (of_property_read_u64_array(power_mgt,
+					       "ibm,cpu-idle-state-psscr-mask",
+						psscr_mask, dt_idle_states)) {
+			pr_warn("cpuidle-powernv:Missing ibm,cpu-idle-state-psscr-mask in DT\n");
+			goto out;
+		}
+	}
+
 	rc = of_property_read_u32_array(power_mgt,
 		"ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);
 
@@ -280,13 +298,13 @@ static int powernv_add_idle_states(void)
 			/* Add NAP state */
 			add_powernv_state(nr_idle_states, "Nap",
 					  CPUIDLE_FLAG_NONE, nap_loop,
-					  target_residency, exit_latency, 0);
+					  target_residency, exit_latency, 0, 0);
 		} else if ((flags[i] & OPAL_PM_STOP_INST_FAST) &&
 				!(flags[i] & OPAL_PM_TIMEBASE_STOP)) {
 			add_powernv_state(nr_idle_states, names[i],
 					  CPUIDLE_FLAG_NONE, stop_loop,
 					  target_residency, exit_latency,
-					  psscr_val[i]);
+					  psscr_val[i], psscr_mask[i]);
 		}
 
 		/*
@@ -302,13 +320,13 @@ static int powernv_add_idle_states(void)
 			add_powernv_state(nr_idle_states, "FastSleep",
 					  CPUIDLE_FLAG_TIMER_STOP,
 					  fastsleep_loop,
-					  target_residency, exit_latency, 0);
+					  target_residency, exit_latency, 0, 0);
 		} else if ((flags[i] & OPAL_PM_STOP_INST_DEEP) &&
 				(flags[i] & OPAL_PM_TIMEBASE_STOP)) {
 			add_powernv_state(nr_idle_states, names[i],
 					  CPUIDLE_FLAG_TIMER_STOP, stop_loop,
 					  target_residency, exit_latency,
-					  psscr_val[i]);
+					  psscr_val[i], psscr_mask[i]);
 		}
 #endif
 		nr_idle_states++;
-- 
1.9.4

Re: [PATCH v3 2/3] cpuidle:powernv: Add helper function to populate powernv idle states.

[Michael Ellerman]

"Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:

> diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> index 7fe442c..9240e08 100644
> --- a/drivers/cpuidle/cpuidle-powernv.c
> +++ b/drivers/cpuidle/cpuidle-powernv.c
> @@ -243,28 +262,31 @@ static int powernv_add_idle_states(void)
>  		 */
>  		if (latency_ns[i] > POWERNV_THRESHOLD_LATENCY_NS)
>  			continue;
> +		/*
> +		 * Firmware passes residency and latency values in ns.
> +		 * cpuidle expects it in us.
> +		 */
> +		exit_latency = ((unsigned int)latency_ns[i]) / 1000;
> +		target_residency = (!rc) ? ((unsigned int)residency_ns[i]) : 0;
> +		target_residency /= 1000;

Urk.

Can you just do it normally:

		if (rc == 0)
			target_residency = (unsigned int)residency_ns[i] / 1000;

I also don't see why you need the cast?

cheers

Re: [PATCH v3 3/3] powernv: Pass PSSCR value and mask to power9_idle_stop

[Michael Ellerman]

"Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:

> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
>
> The power9_idle_stop method currently takes only the requested stop
> level as a parameter and picks up the rest of the PSSCR bits from a
> hand-coded macro. This is not a very flexible design, especially when
> the firmware has the capability to communicate the psscr value and the
> mask associated with a particular stop state via device tree.
>
> This patch modifies the power9_idle_stop API to take as parameters the
> PSSCR value and the PSSCR mask corresponding to the stop state that
> needs to be set. These PSSCR value and mask are respectively obtained
> by parsing the "ibm,cpu-idle-state-psscr" and
> "ibm,cpu-idle-state-psscr-mask" fields from the device tree.
>
> In addition to this, the patch adds support for handling stop states
> for which ESL and EC bits in the PSSCR are zero. As per the
> architecture, a wakeup from these stop states resumes execution from
> the subsequent instruction as opposed to waking up at the System
> Vector.
>
> The older firmware sets only the Requested Level (RL) field in the
> psscr and psscr-mask exposed in the device tree. For older firmware
> where psscr-mask=0xf, this patch will set the default sane values that
> the set for for remaining PSSCR fields (i.e PSLL, MTL, ESL, EC, and
> TR).

So we're using psscr-mas=0xf as a signal that we're running on old
firmware.

That's OK I think, but please send a patch to document it in the device
tree binding.

And call it out below in the code.

cheers

Re: [PATCH v3 2/3] cpuidle:powernv: Add helper function to populate powernv idle states.

[Gautham R Shenoy]

Hi Michael,

On Wed, Nov 23, 2016 at 08:49:08PM +1100, Michael Ellerman wrote:
> "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:
> 
> > diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> > index 7fe442c..9240e08 100644
> > --- a/drivers/cpuidle/cpuidle-powernv.c
> > +++ b/drivers/cpuidle/cpuidle-powernv.c
> > @@ -243,28 +262,31 @@ static int powernv_add_idle_states(void)
> >  		 */
> >  		if (latency_ns[i] > POWERNV_THRESHOLD_LATENCY_NS)
> >  			continue;
> > +		/*
> > +		 * Firmware passes residency and latency values in ns.
> > +		 * cpuidle expects it in us.
> > +		 */
> > +		exit_latency = ((unsigned int)latency_ns[i]) / 1000;
> > +		target_residency = (!rc) ? ((unsigned int)residency_ns[i]) : 0;
> > +		target_residency /= 1000;
> 
> Urk.
> 
> Can you just do it normally:
> 
> 		if (rc == 0)
> 			target_residency = (unsigned int)residency_ns[i] / 1000;

Wrote this in a non-standard manner since the normal way would exceed
80 chars.

> 
> I also don't see why you need the cast?

It is a remnant from the previous code. But I see your point, the cast
is redundant, and removing it will make it possible to implement this
in the normal manner without checkpatch warning about it.

> 
> cheers
> 

--
Thanks and Regards
gautham.

Re: [PATCH v3 3/3] powernv: Pass PSSCR value and mask to power9_idle_stop

[Gautham R Shenoy]

Hi Michael,

On Wed, Nov 23, 2016 at 08:51:10PM +1100, Michael Ellerman wrote:
> "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:
> 
> > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> >
> > The power9_idle_stop method currently takes only the requested stop
> > level as a parameter and picks up the rest of the PSSCR bits from a
> > hand-coded macro. This is not a very flexible design, especially when
> > the firmware has the capability to communicate the psscr value and the
> > mask associated with a particular stop state via device tree.
> >
> > This patch modifies the power9_idle_stop API to take as parameters the
> > PSSCR value and the PSSCR mask corresponding to the stop state that
> > needs to be set. These PSSCR value and mask are respectively obtained
> > by parsing the "ibm,cpu-idle-state-psscr" and
> > "ibm,cpu-idle-state-psscr-mask" fields from the device tree.
> >
> > In addition to this, the patch adds support for handling stop states
> > for which ESL and EC bits in the PSSCR are zero. As per the
> > architecture, a wakeup from these stop states resumes execution from
> > the subsequent instruction as opposed to waking up at the System
> > Vector.
> >
> > The older firmware sets only the Requested Level (RL) field in the
> > psscr and psscr-mask exposed in the device tree. For older firmware
> > where psscr-mask=0xf, this patch will set the default sane values that
> > the set for for remaining PSSCR fields (i.e PSLL, MTL, ESL, EC, and
> > TR).
> 
> So we're using psscr-mas=0xf as a signal that we're running on old
> firmware.
> 
> That's OK I think, but please send a patch to document it in the device
> tree binding.
> 
> And call it out below in the code.

Sure will do this! Thanks for reviewing the code.

> 
> cheers
> 

--
Thanks and Regards
gautham.

Re: [PATCH v3 0/3] powernv:stop: Use psscr_val,mask provided by firmware

[Balbir Singh]

On 10/11/16 18:54, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> 
> This is the third iteration of the patchset to use the psscr_val and
> psscr_mask provided by the firmware for each of the stop states.
> 
> The previous version can be found here:
> 
> [v2]: https://lkml.org/lkml/2016/10/27/143
> [v1]: https://lkml.org/lkml/2016/9/29/45
> 
> This version fixes a couple of bugs pertaining to strncpy and
> initialization of the target-residency values of nap and sleep
> which were pointed out by Paul and Oliver in the earlier version.
> 
> Synopsis
> ==========
> In the current implementation, the code for ISA
> v3.0 stop implementation has a couple of shortcomings.
> 
> a) The code hand-codes the values for ESL,EC,TR,MTL bits of PSSCR and
>    uses only the RL field from the firmware. While this is not
>    incorrect, since the hand-coded values are legitimate, it is not a
>    very flexible design since the firmware has the capability to
>    communicate these values via the "ibm,cpu-idle-state-psscr" and
>    "ibm,cpu-idle-state-psscr-mask" properties. In case where the
>    firmware provides values for these fields that is different from
>    the hand-coded values, the current code will not work as intended.
> 
> b) Due to issue a), the current code assumes that ESL=EC=1 for all the
>    stop states and hence the wakeup from the stop instruction will
>    happen at 0x100, the system-reset vector. However, the ISA v3.0
>    allows the ESL=EC=0 behaviour where the corresponding stop-state
>    loses no state and wakes up from the subsequent instruction. The
>    current code doesn't handle this case.
>    

Sounds reasonable

Balbir Singh.

Re: [PATCH v3 1/3] powernv:idle: Add IDLE_STATE_ENTER_SEQ_NORET macro

[Balbir Singh]

On 10/11/16 18:54, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> 
> Currently all the low-power idle states are expected to wake up
> at reset vector 0x100. Which is why the macro IDLE_STATE_ENTER_SEQ
> that puts the CPU to an idle state and never returns.
> 
> On ISA_300, when the ESL and EC bits in the PSSCR are zero, the
> CPU is expected to wake up at the next instruction of the idle
> instruction.
> 
> This patch adds a new macro named IDLE_STATE_ENTER_SEQ_NORET for the

I think something like IDLE_STATE_ENTER_SEQ_LOSE_CTX would be better?

> no-return variant and reuses the name IDLE_STATE_ENTER_SEQ
> for a variant that allows resuming operation at the instruction next
> to the idle-instruction.
> 
<snip>
> +
> +#define	IDLE_STATE_ENTER_SEQ_NORET(IDLE_INST)			\
> +	IDLE_STATE_ENTER_SEQ(IDLE_INST)                         \

So we start off with both as the same?

>  	b	.
>  #endif /* CONFIG_PPC_P7_NAP */
<snip>
Balbir

Re: [PATCH v3 1/3] powernv:idle: Add IDLE_STATE_ENTER_SEQ_NORET macro

[Gautham R Shenoy]

Hi Balbir,

On Tue, Nov 29, 2016 at 09:42:20PM +1100, Balbir Singh wrote:
> 
> 
> On 10/11/16 18:54, Gautham R. Shenoy wrote:
> > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> > 
> > Currently all the low-power idle states are expected to wake up
> > at reset vector 0x100. Which is why the macro IDLE_STATE_ENTER_SEQ
> > that puts the CPU to an idle state and never returns.
> > 
> > On ISA_300, when the ESL and EC bits in the PSSCR are zero, the
> > CPU is expected to wake up at the next instruction of the idle
> > instruction.
> > 
> > This patch adds a new macro named IDLE_STATE_ENTER_SEQ_NORET for the
> 
> I think something like IDLE_STATE_ENTER_SEQ_LOSE_CTX would be better?

As you pointed out below, the macro encapsulates the magic sequence
that needs to be executed to go to a particular idle-state.

The behaviour changes based on ESL=EC=1 (or nap,fastsleep,winkle on
POWER8) in which case wake up is at 0x100. When ESL=EC=0, the wakeup
happens at the subsequent instruction.

So, more than whether the context is lost or not, the intent is to
indicate whether the wakeup happens at the next instruction or at
0x100.

> 
> > no-return variant and reuses the name IDLE_STATE_ENTER_SEQ
> > for a variant that allows resuming operation at the instruction next
> > to the idle-instruction.
> > 
> <snip>
> > +
> > +#define	IDLE_STATE_ENTER_SEQ_NORET(IDLE_INST)			\
> > +	IDLE_STATE_ENTER_SEQ(IDLE_INST)                         \
> 
> So we start off with both as the same?
> 
> >  	b	.
> >  #endif /* CONFIG_PPC_P7_NAP */
> <snip>
> Balbir
> 
--
Thanks and Regards
gautham.