cpuidle/powernv: Add support for POWER ISA v3 idle states

POWER ISA v3 defines a new idle processor core mechanism. In summary,
 a) new instruction named stop is added.
 b) new per thread SPR named PSSCR is added which controls the behavior
	of stop instruction.

Supported idle states and value to be written to PSSCR register to enter
any idle state is exposed via ibm,cpu-idle-state-names and
ibm,cpu-idle-state-psscr respectively. To enter an idle state,
platform provided power_stop() needs to be invoked with the appropriate
PSSCR value.

This patch adds support for this new mechanism in cpuidle powernv driver.

Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Cc: linux-pm@vger.kernel.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: linuxppc-dev@lists.ozlabs.org
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/cpuidle/cpuidle-powernv.c

@@ -20,13 +20,18 @@
 #include <asm/opal.h>
 #include <asm/runlatch.h>
 
+#define POWERNV_THRESHOLD_LATENCY_NS 200000
+
 struct cpuidle_driver powernv_idle_driver = {
 	.name             = "powernv_idle",
 	.owner            = THIS_MODULE,
 };
 
 static int max_idle_state;
 static struct cpuidle_state *cpuidle_state_table;
+
+static u64 stop_psscr_table[CPUIDLE_STATE_MAX];
+
 static u64 snooze_timeout;
 static bool snooze_timeout_en;
 
@@ -91,6 +96,17 @@ static int fastsleep_loop(struct cpuidle_device *dev,
 	return index;
 }
 #endif
+
+static int stop_loop(struct cpuidle_device *dev,
+		     struct cpuidle_driver *drv,
+		     int index)
+{
+	ppc64_runlatch_off();
+	power9_idle_stop(stop_psscr_table[index]);
+	ppc64_runlatch_on();
+	return index;
+}
+
 /*
  * States for dedicated partition case.
  */
@@ -169,6 +185,8 @@ static int powernv_add_idle_states(void)
 	u32 latency_ns[CPUIDLE_STATE_MAX];
 	u32 residency_ns[CPUIDLE_STATE_MAX];
 	u32 flags[CPUIDLE_STATE_MAX];
+	u64 psscr_val[CPUIDLE_STATE_MAX];
+	const char *names[CPUIDLE_STATE_MAX];
 	int i, rc;
 
 	/* Currently we have snooze statically defined */
@@ -207,11 +225,34 @@ static int powernv_add_idle_states(void)
 		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-latencies-ns in DT\n");
 		goto out;
 	}
+	if (of_property_read_string_array(power_mgt,
+		"ibm,cpu-idle-state-names", names, dt_idle_states) < 0) {
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-names in DT\n");
+		goto out;
+	}
+
+	/*
+	 * If the idle states use stop instruction, probe for psscr values
+	 * which are necessary to specify required stop level.
+	 */
+	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");
+			goto out;
+		}
 
 	rc = of_property_read_u32_array(power_mgt,
 		"ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);
 
 	for (i = 0; i < dt_idle_states; i++) {
+		/*
+		 * If an idle state has exit latency beyond
+		 * POWERNV_THRESHOLD_LATENCY_NS then don't use it
+		 * in cpu-idle.
+		 */
+		if (latency_ns[i] > POWERNV_THRESHOLD_LATENCY_NS)
+			continue;
 
 		/*
 		 * Cpuidle accepts exit_latency and target_residency in us.
@@ -224,6 +265,16 @@ static int powernv_add_idle_states(void)
 			powernv_states[nr_idle_states].flags = 0;
 			powernv_states[nr_idle_states].target_residency = 100;
 			powernv_states[nr_idle_states].enter = nap_loop;
+		} 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];
 		}
 
 		/*
@@ -239,6 +290,16 @@ static int powernv_add_idle_states(void)
 			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;
+		} 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];
 		}
 #endif
 		powernv_states[nr_idle_states].exit_latency =