Re: [PATCH v4 09/10] 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 <redacted>
Cc: Daniel Lezcano <redacted>
Cc: linux-pm@vger.kernel.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <redacted>
Cc: linuxppc-dev@lists.ozlabs.org
Reviewed-by: Gautham R. Shenoy <redacted>
Signed-off-by: Shreyas B. Prabhu <redacted>
---
  - No changes since v1

  drivers/cpuidle/cpuidle-powernv.c | 57 ++++++++++++++++++++++++++++++++++++++-
  1 file changed, 56 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index e12dc30..efe5221 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c

@@ -21,6 +21,7 @@
  #include <asm/runlatch.h>

  #define MAX_POWERNV_IDLE_STATES	8
+#define MAX_IDLE_STATE_NAME_LEN	10

  struct cpuidle_driver powernv_idle_driver = {
  	.name             = "powernv_idle",

@@ -29,9 +30,11 @@ struct cpuidle_driver powernv_idle_driver = {

  static int max_idle_state;
  static struct cpuidle_state *cpuidle_state_table;
+
+static u64 stop_psscr_table[MAX_POWERNV_IDLE_STATES];
+
  static u64 snooze_timeout;
  static bool snooze_timeout_en;
-
  static int snooze_loop(struct cpuidle_device *dev,
  			struct cpuidle_driver *drv,
  			int index)

@@ -139,6 +142,15 @@ static struct notifier_block setup_hotplug_notifier = {
  	.notifier_call = powernv_cpuidle_add_cpu_notifier,
  };

+static int stop_loop(struct cpuidle_device *dev,
+			struct cpuidle_driver *drv,
+			int index)
+{
+	ppc64_runlatch_off();
+	power_stop(stop_psscr_table[index]);
+	ppc64_runlatch_on();
+	return index;
+}
  /*
   * powernv_cpuidle_driver_init()
   */

@@ -169,6 +181,8 @@ static int powernv_add_idle_states(void)
  	int nr_idle_states = 1; /* Snooze */
  	int dt_idle_states;
  	u32 *latency_ns, *residency_ns, *flags;
+	u64 *psscr_val = NULL;
+	const char *names[MAX_POWERNV_IDLE_STATES];
  	int i, rc;

  	/* Currently we have snooze statically defined */

@@ -201,6 +215,23 @@ static int powernv_add_idle_states(void)
  		goto out_free_latency;
  	}

+	rc = of_property_read_string_array(power_mgt,
+		"ibm,cpu-idle-state-names", names, dt_idle_states);
+	if (rc < -1) {

+		if (rc < -1) {
+			pr_warn("cpuidle-powernv: missing ibm,cpu-idle-states-psscr in DT\n");
+			goto out_free_psscr;
+		}
+	}
  	residency_ns = kzalloc(sizeof(*residency_ns) * dt_idle_states, GFP_KERNEL);
  	rc = of_property_read_u32_array(power_mgt,
  		"ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);

@@ -218,6 +249,16 @@ 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,
+				(char *)names[i], MAX_IDLE_STATE_NAME_LEN);

+			stop_psscr_table[nr_idle_states] = psscr_val[i];
  		}

  		/*

@@ -233,6 +274,18 @@ 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,
+				(char *)names[i], MAX_IDLE_STATE_NAME_LEN);
+			strncpy(powernv_states[nr_idle_states].desc,
+				(char *)names[i], MAX_IDLE_STATE_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 =

@@ -247,6 +300,8 @@ static int powernv_add_idle_states(void)
  	}

  	kfree(residency_ns);
+out_free_psscr:
+	kfree(psscr_val);
  out_free_latency:
  	kfree(latency_ns);
  out_free_flags: