[PATCH v3] cpufreq: powernv: Add support of frequency domain

[Abhishek Goel]

Frequency-domain indicates group of CPUs that would share same frequency.
It is detected using device-tree node "frequency-domain-indicator".
frequency-domain-indicator is a bitmask which will have different value
depending upon the generation of the processor.

CPUs of the same chip for which the result of a bitwise AND between
their PIR and the frequency-domain-indicator is the same share the same
frequency.

In this patch, we define hash-table indexed by the aforementioned
bitwise ANDed value to store the cpumask of the CPUs sharing the same
frequency domain. Further, the cpufreq policy will be created per
frequency-domain

So for POWER9, a cpufreq policy is created per quad while for POWER8 it
is created per core. Governor decides frequency for each policy but
multiple cores may come under same policy. In such case frequency needs
to be set on each core sharing that policy.

Signed-off-by: Abhishek Goel <huntbag@xxxxxxxxxxxxxxxxxx>
---

Skiboot patch required for the corresponding device-tree changes have been
posted here : http://patchwork.ozlabs.org/patch/862256/

 drivers/cpufreq/powernv-cpufreq.c | 104 ++++++++++++++++++++++++++++++++++----
 1 file changed, 95 insertions(+), 9 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index b6d7c4c..aab23a4 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -37,6 +37,7 @@
 #include <asm/smp.h> /* Required for cpu_sibling_mask() in UP configs */
 #include <asm/opal.h>
 #include <linux/timer.h>
+#include <linux/hashtable.h>
 
 #define POWERNV_MAX_PSTATES	256
 #define PMSR_PSAFE_ENABLE	(1UL << 30)
@@ -130,6 +131,9 @@ enum throttle_reason_type {
 static int nr_chips;
 static DEFINE_PER_CPU(struct chip *, chip_info);
 
+static u32 freq_domain_indicator;
+static bool p9_occ_quirk;
+
 /*
  * Note:
  * The set of pstates consists of contiguous integers.
@@ -194,6 +198,38 @@ static inline void reset_gpstates(struct cpufreq_policy *policy)
 	gpstates->last_gpstate_idx = 0;
 }
 
+#define SIZE NR_CPUS
+#define ORDER_FREQ_MAP ilog2(SIZE)
+
+static DEFINE_HASHTABLE(freq_domain_map, ORDER_FREQ_MAP);
+
+struct hashmap {
+	cpumask_t mask;
+	int chip_id;
+	u32 pir_key;
+	struct hlist_node hash_node;
+};
+
+static void insert(u32 key, int cpu)
+{
+	struct hashmap *data;
+
+	hash_for_each_possible(freq_domain_map, data, hash_node, key%SIZE) {
+		if (data->chip_id == cpu_to_chip_id(cpu) &&
+			data->pir_key == key) {
+			cpumask_set_cpu(cpu, &data->mask);
+			return;
+		}
+	}
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	hash_add(freq_domain_map, &data->hash_node, key%SIZE);
+	cpumask_set_cpu(cpu, &data->mask);
+	data->chip_id = cpu_to_chip_id(cpu);
+	data->pir_key = key;
+
+}
+
 /*
  * Initialize the freq table based on data obtained
  * from the firmware passed via device-tree
@@ -206,6 +242,7 @@ static int init_powernv_pstates(void)
 	u32 len_ids, len_freqs;
 	u32 pstate_min, pstate_max, pstate_nominal;
 	u32 pstate_turbo, pstate_ultra_turbo;
+	u32 key;
 
 	power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
 	if (!power_mgt) {
@@ -246,9 +283,18 @@ static int init_powernv_pstates(void)
 	else
 		powernv_pstate_info.wof_enabled = true;
 
+	if (of_device_is_compatible(power_mgt, "freq-domain-v1") &&
+		of_property_read_u32(power_mgt, "ibm,freq-domain-indicator",
+				&freq_domain_indicator))
+		pr_warn("ibm,freq-domain-indicator not found\n");
+
+        if (of_device_is_compatible(power_mgt, "p9-occ-quirk"))
+		p9_occ_quirk = true;
+
 next:
 	pr_info("cpufreq pstate min %d nominal %d max %d\n", pstate_min,
 		pstate_nominal, pstate_max);
+	pr_info("frequency domain indicator %d", freq_domain_indicator);
 	pr_info("Workload Optimized Frequency is %s in the platform\n",
 		(powernv_pstate_info.wof_enabled) ? "enabled" : "disabled");
 
@@ -276,6 +322,15 @@ static int init_powernv_pstates(void)
 		return -ENODEV;
 	}
 
+	if (freq_domain_indicator) {
+		hash_init(freq_domain_map);
+		for_each_possible_cpu(i) {
+			key = ((u32) get_hard_smp_processor_id(i) &
+				freq_domain_indicator);
+			insert(key, i);
+		}
+	}
+
 	powernv_pstate_info.nr_pstates = nr_pstates;
 	pr_debug("NR PStates %d\n", nr_pstates);
 	for (i = 0; i < nr_pstates; i++) {
@@ -760,25 +815,56 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
 
 	spin_unlock(&gpstates->gpstate_lock);
 
-	/*
-	 * Use smp_call_function to send IPI and execute the
-	 * mtspr on target CPU.  We could do that without IPI
-	 * if current CPU is within policy->cpus (core)
+	/* The current DVFS implementation in firmware requires that to set a
+	 * frequency in a quad, all cores of the quad need to set frequency in
+	 * their respective PMCR's. Ideally setting frequency on any of the
+	 * core of that quad should change frequency for the quad.
 	 */
-	smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
+	if (p9_occ_quirk) {
+		cpumask_t temp;
+		u32 cpu;
+
+		cpumask_copy(&temp, policy->cpus);
+		while (!cpumask_empty(&temp)) {
+			cpu = cpumask_first(&temp);
+			smp_call_function_any(cpu_sibling_mask(cpu),
+					set_pstate, &freq_data, 1);
+			cpumask_andnot(&temp, &temp, cpu_sibling_mask(cpu));
+		}
+	} else {
+		smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
+	}
+
 	return 0;
 }
 
 static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
 {
-	int base, i, ret;
+	int ret;
 	struct kernfs_node *kn;
 	struct global_pstate_info *gpstates;
 
-	base = cpu_first_thread_sibling(policy->cpu);
+	if (!freq_domain_indicator) {
+		int base, i;
 
-	for (i = 0; i < threads_per_core; i++)
-		cpumask_set_cpu(base + i, policy->cpus);
+		base = cpu_first_thread_sibling(policy->cpu);
+		for (i = 0; i < threads_per_core; i++)
+			cpumask_set_cpu(base + i, policy->cpus);
+	} else {
+		u32 key;
+		struct hashmap *data;
+
+		key = ((u32) get_hard_smp_processor_id(policy->cpu) &
+				freq_domain_indicator);
+		hash_for_each_possible(freq_domain_map, data, hash_node,
+								 key%SIZE) {
+			if (data->chip_id == cpu_to_chip_id(policy->cpu) &&
+				data->pir_key == key) {
+				cpumask_copy(policy->cpus, &data->mask);
+				break;
+			}
+		}
+	}
 
 	kn = kernfs_find_and_get(policy->kobj.sd, throttle_attr_grp.name);
 	if (!kn) {
-- 
1.8.3.1