PSCI: Decouple PSCI stat residency calculation from PMF

This patch introduces the following three platform interfaces:

* void plat_psci_stat_accounting_start(const psci_power_state_t *state_info)

  This is an optional hook that platforms can implement in order
  to perform accounting before entering a low power state.  This
  typically involves capturing a timestamp.

* void plat_psci_stat_accounting_stop(const psci_power_state_t *state_info)

  This is an optional hook that platforms can implement in order
  to perform accounting after exiting from a low power state.  This
  typically involves capturing a timestamp.

* u_register_t plat_psci_stat_get_residency(unsigned int lvl,
	const psci_power_state_t *state_info,
	unsigned int last_cpu_index)

  This is an optional hook that platforms can implement in order
  to calculate the PSCI stat residency.

If any of these interfaces are overridden by the platform, it is
recommended that all of them are.

By default `ENABLE_PSCI_STAT` is disabled.  If `ENABLE_PSCI_STAT`
is set but `ENABLE_PMF` is not set then an alternative PSCI stat
collection backend must be provided.  If both are set, then default
weak definitions of these functions are provided, using PMF to
calculate the residency.

NOTE: Previously, platforms did not have to explicitly set
`ENABLE_PMF` since this was automatically done by the top-level
Makefile.

Change-Id: I17b47804dea68c77bc284df15ee1ccd66bc4b79b
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

1 files changed, 118 insertions, 1 deletions

diff --git a/plat/common/plat_psci_common.c b/plat/common/plat_psci_common.c
index 3eb6886e..0e00faaf 100644
--- a/plat/common/plat_psci_common.c
+++ b/plat/common/plat_psci_common.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -31,8 +31,125 @@
 #include <arch.h>
 #include <assert.h>
 #include <platform.h>
+#include <pmf.h>
 #include <psci.h>
 
+#if ENABLE_PSCI_STAT && ENABLE_PMF
+#pragma weak plat_psci_stat_accounting_start
+#pragma weak plat_psci_stat_accounting_stop
+#pragma weak plat_psci_stat_get_residency
+
+/* Ticks elapsed in one second by a signal of 1 MHz */
+#define MHZ_TICKS_PER_SEC 1000000
+
+/* Following are used as ID's to capture time-stamp */
+#define PSCI_STAT_ID_ENTER_LOW_PWR		0
+#define PSCI_STAT_ID_EXIT_LOW_PWR		1
+#define PSCI_STAT_TOTAL_IDS			2
+
+PMF_REGISTER_SERVICE(psci_svc, PMF_PSCI_STAT_SVC_ID, PSCI_STAT_TOTAL_IDS,
+	PMF_STORE_ENABLE)
+
+/*
+ * This function calculates the stats residency in microseconds,
+ * taking in account the wrap around condition.
+ */
+static u_register_t calc_stat_residency(unsigned long long pwrupts,
+	unsigned long long pwrdnts)
+{
+	/* The divisor to use to convert raw timestamp into microseconds. */
+	u_register_t residency_div;
+	u_register_t res;
+
+	/*
+	 * Calculate divisor so that it can be directly used to
+	 * convert time-stamp into microseconds.
+	 */
+	residency_div = read_cntfrq_el0() / MHZ_TICKS_PER_SEC;
+	assert(residency_div);
+
+	if (pwrupts < pwrdnts)
+		res = UINT64_MAX - pwrdnts + pwrupts;
+	else
+		res = pwrupts - pwrdnts;
+
+	return res / residency_div;
+}
+
+/*
+ * Capture timestamp before entering a low power state.
+ * No cache maintenance is required when capturing the timestamp.
+ * Cache maintenance may be needed when reading these timestamps.
+ */
+void plat_psci_stat_accounting_start(
+	__unused const psci_power_state_t *state_info)
+{
+	assert(state_info);
+	PMF_CAPTURE_TIMESTAMP(psci_svc, PSCI_STAT_ID_ENTER_LOW_PWR,
+		PMF_NO_CACHE_MAINT);
+}
+
+/*
+ * Capture timestamp after exiting a low power state.
+ * No cache maintenance is required when capturing the timestamp.
+ * Cache maintenance may be needed when reading these timestamps.
+ */
+void plat_psci_stat_accounting_stop(
+	__unused const psci_power_state_t *state_info)
+{
+	assert(state_info);
+	PMF_CAPTURE_TIMESTAMP(psci_svc, PSCI_STAT_ID_EXIT_LOW_PWR,
+		PMF_NO_CACHE_MAINT);
+}
+
+/*
+ * Calculate the residency for the given level and power state
+ * information.
+ */
+u_register_t plat_psci_stat_get_residency(unsigned int lvl,
+	const psci_power_state_t *state_info,
+	int last_cpu_idx)
+{
+	plat_local_state_t state;
+	unsigned long long pwrup_ts = 0, pwrdn_ts = 0;
+	unsigned int pmf_flags;
+
+	assert(lvl >= PSCI_CPU_PWR_LVL && lvl <= PLAT_MAX_PWR_LVL);
+	assert(state_info);
+	assert(last_cpu_idx >= 0 && last_cpu_idx <= PLATFORM_CORE_COUNT);
+
+	if (lvl == PSCI_CPU_PWR_LVL)
+		assert(last_cpu_idx == plat_my_core_pos());
+
+	/*
+	 * If power down is requested, then timestamp capture will
+	 * be with caches OFF.  Hence we have to do cache maintenance
+	 * when reading the timestamp.
+	 */
+	state = state_info->pwr_domain_state[PSCI_CPU_PWR_LVL];
+	if (is_local_state_off(state)) {
+		pmf_flags = PMF_CACHE_MAINT;
+	} else {
+		assert(is_local_state_retn(state));
+		pmf_flags = PMF_NO_CACHE_MAINT;
+	}
+
+	PMF_GET_TIMESTAMP_BY_INDEX(psci_svc,
+		PSCI_STAT_ID_ENTER_LOW_PWR,
+		last_cpu_idx,
+		pmf_flags,
+		pwrdn_ts);
+
+	PMF_GET_TIMESTAMP_BY_INDEX(psci_svc,
+		PSCI_STAT_ID_EXIT_LOW_PWR,
+		plat_my_core_pos(),
+		pmf_flags,
+		pwrup_ts);
+
+	return calc_stat_residency(pwrup_ts, pwrdn_ts);
+}
+#endif /* ENABLE_PSCI_STAT && ENABLE_PMF */
+
 /*
  * The PSCI generic code uses this API to let the platform participate in state
  * coordination during a power management operation. It compares the platform