[Skiboot] [RFC 1/3] Interface for an idle-stop dependency structure

[Pratik Rajesh Sampat]

Design patch to introduce the idea of having a dependency structure for
idle-stop. The structure encapsulates the following:
1. Bitmask for version of idle-stop
2. Bitmask for propterties like ENABLE/DISABLE
3. Function pointer which helps handle how the stop must be invoked

The commit lays a foundation for other idle-stop versions to be added
and handled cleanly based on their specified requirments.
Currently it handles the existing "idle-stop" version by setting the
discovery bits and the function pointer.

Signed-off-by: Pratik Rajesh Sampat <psampat at linux.ibm.com>
---
 arch/powerpc/include/asm/processor.h  | 17 +++++++++++++++++
 arch/powerpc/kernel/dt_cpu_ftrs.c     |  5 +++++
 arch/powerpc/platforms/powernv/idle.c | 17 +++++++++++++----
 drivers/cpuidle/cpuidle-powernv.c     |  3 ++-
 4 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index eedcbfb9a6ff..da59f01a5c09 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -429,6 +429,23 @@ extern void power4_idle_nap(void);
 extern unsigned long cpuidle_disable;
 enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};
 
+#define STOP_ENABLE		0x00000001
+
+#define STOP_VERSION_P9       0x1
+
+/*
+ * Classify the dependencies of the stop states
+ * @idle_stop: function handler to handle the quirk stop version
+ * @cpuidle_prop: Signify support for stop states through kernel and/or firmware
+ * @stop_version: Classify quirk versions for stop states
+ */
+typedef struct {
+	unsigned long (*idle_stop)(unsigned long, bool);
+	uint8_t cpuidle_prop;
+	uint8_t stop_version;
+}stop_deps_t;
+extern stop_deps_t stop_dep;
+
 extern int powersave_nap;	/* set if nap mode can be used in idle loop */
 
 extern void power7_idle_type(unsigned long type);
diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
index 182b4047c1ef..db1a525e090d 100644
--- a/arch/powerpc/kernel/dt_cpu_ftrs.c
+++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
@@ -292,6 +292,8 @@ static int __init feat_enable_idle_stop(struct dt_cpu_feature *f)
 	lpcr |=  LPCR_PECE1;
 	lpcr |=  LPCR_PECE2;
 	mtspr(SPRN_LPCR, lpcr);
+	stop_dep.cpuidle_prop |= STOP_ENABLE;
+	stop_dep.stop_version = STOP_VERSION_P9;
 
 	return 1;
 }
@@ -657,6 +659,9 @@ static void __init cpufeatures_setup_start(u32 isa)
 	}
 }
 
+stop_deps_t stop_dep = {NULL, 0x0, 0x0};
+EXPORT_SYMBOL(stop_dep);
+
 static bool __init cpufeatures_process_feature(struct dt_cpu_feature *f)
 {
 	const struct dt_cpu_feature_match *m;
diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 78599bca66c2..c32cdc37acf4 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -812,7 +812,7 @@ static unsigned long power9_offline_stop(unsigned long psscr)
 
 #ifndef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 	__ppc64_runlatch_off();
-	srr1 = power9_idle_stop(psscr, true);
+	srr1 = stop_dep.idle_stop(psscr, true);
 	__ppc64_runlatch_on();
 #else
 	/*
@@ -828,7 +828,7 @@ static unsigned long power9_offline_stop(unsigned long psscr)
 	local_paca->kvm_hstate.hwthread_state = KVM_HWTHREAD_IN_IDLE;
 
 	__ppc64_runlatch_off();
-	srr1 = power9_idle_stop(psscr, false);
+	srr1 = stop_dep.idle_stop(psscr, true);
 	__ppc64_runlatch_on();
 
 	local_paca->kvm_hstate.hwthread_state = KVM_HWTHREAD_IN_KERNEL;
@@ -856,7 +856,7 @@ void power9_idle_type(unsigned long stop_psscr_val,
 	psscr = (psscr & ~stop_psscr_mask) | stop_psscr_val;
 
 	__ppc64_runlatch_off();
-	srr1 = power9_idle_stop(psscr, true);
+	srr1 = stop_dep.idle_stop(psscr, true);
 	__ppc64_runlatch_on();
 
 	fini_irq_for_idle_irqsoff();
@@ -1353,8 +1353,17 @@ static int __init pnv_init_idle_states(void)
 	nr_pnv_idle_states = 0;
 	supported_cpuidle_states = 0;
 
-	if (cpuidle_disable != IDLE_NO_OVERRIDE)
+	if (cpuidle_disable != IDLE_NO_OVERRIDE ||
+	    !(stop_dep.cpuidle_prop & STOP_ENABLE))
 		goto out;
+	switch(stop_dep.stop_version) {
+	case STOP_VERSION_P9:
+		stop_dep.idle_stop = power9_idle_stop;
+		break;
+	default:
+		stop_dep.idle_stop = NULL;
+		goto out;
+	}
 	rc = pnv_parse_cpuidle_dt();
 	if (rc)
 		return rc;
diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 1b299e801f74..7430a8edf5c9 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -371,7 +371,8 @@ static int powernv_add_idle_states(void)
  */
 static int powernv_idle_probe(void)
 {
-	if (cpuidle_disable != IDLE_NO_OVERRIDE)
+	if (cpuidle_disable != IDLE_NO_OVERRIDE ||
+	    !(stop_dep.cpuidle_prop & STOP_ENABLE))
 		return -ENODEV;
 
 	if (firmware_has_feature(FW_FEATURE_OPAL)) {
-- 
2.24.1