[PATCH v2] cpufreq: powernv: Replacing pstate_id with frequency table index

[Akshay Adiga]

Refactoring code to use frequency table index instead of pstate_id.
This abstraction will make the code independent of the pstate values.

- No functional changes
- The highest frequency is at frequency table index 0 and the frequency
  decreases as the index increases.
- Macros pstates_to_idx() and idx_to_pstate() can be used for conversion
  between pstate_id and index.
- powernv_pstate_info now contains frequency table index to min, max and
  nominal frequency (instead of pstate_ids)
- global_pstate_info new stores index values instead pstate ids.
- variables renamed as *_idx which now store index instead of pstate

Signed-off-by: Akshay Adiga <akshay.adiga@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
---
Changes from v1:
  - changed macro names from get_pstate()/ get_index() to 
idx_to_pstate()/ pstate_to_idx()
  - Renamed variables that store index instead of pstate_id to *_idx
  - Retained previous printk's 

v1 : http://marc.info/?l=linux-pm&m=146677701501225&w=1

 drivers/cpufreq/powernv-cpufreq.c | 177 ++++++++++++++++++++++----------------
 1 file changed, 102 insertions(+), 75 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index b29c5c2..72c91d8 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -64,12 +64,14 @@
 /**
  * struct global_pstate_info -	Per policy data structure to maintain history of
  *				global pstates
- * @highest_lpstate:		The local pstate from which we are ramping down
+ * @highest_lpstate_idx:	The local pstate index from which we are
+ *				ramping down
  * @elapsed_time:		Time in ms spent in ramping down from
- *				highest_lpstate
+ *				highest_lpstate_idx
  * @last_sampled_time:		Time from boot in ms when global pstates were
  *				last set
- * @last_lpstate,last_gpstate:	Last set values for local and global pstates
+ * @last_lpstate_idx,		Last set value of local pstate and global
+ * last_gpstate_idx		pstate in terms of cpufreq table index
  * @timer:			Is used for ramping down if cpu goes idle for
  *				a long time with global pstate held high
  * @gpstate_lock:		A spinlock to maintain synchronization between
@@ -77,11 +79,11 @@
  *				governer's target_index calls
  */
 struct global_pstate_info {
-	int highest_lpstate;
+	int highest_lpstate_idx;
 	unsigned int elapsed_time;
 	unsigned int last_sampled_time;
-	int last_lpstate;
-	int last_gpstate;
+	int last_lpstate_idx;
+	int last_gpstate_idx;
 	spinlock_t gpstate_lock;
 	struct timer_list timer;
 };
@@ -124,29 +126,47 @@ static int nr_chips;
 static DEFINE_PER_CPU(struct chip *, chip_info);
 
 /*
- * Note: The set of pstates consists of contiguous integers, the
- * smallest of which is indicated by powernv_pstate_info.min, the
- * largest of which is indicated by powernv_pstate_info.max.
+ * Note:
+ * The set of pstates consists of contiguous integers.
+ * powernv_pstate_info stores the index of the frequency table for
+ * max, min and nominal frequencies. It also stores number of
+ * available frequencies.
  *
- * The nominal pstate is the highest non-turbo pstate in this
- * platform. This is indicated by powernv_pstate_info.nominal.
+ * powernv_pstate_info.nominal indicates the index to the highest
+ * non-turbo frequency.
  */
 static struct powernv_pstate_info {
-	int min;
-	int max;
-	int nominal;
-	int nr_pstates;
+	unsigned int min;
+	unsigned int max;
+	unsigned int nominal;
+	unsigned int nr_pstates;
 } powernv_pstate_info;
 
+/* Use following macros for conversions between pstate_id and index */
+static inline int idx_to_pstate(unsigned int i)
+{
+	return powernv_freqs[i].driver_data;
+}
+
+static inline unsigned int pstate_to_idx(int pstate)
+{
+	/*
+	 * abs() is deliberately used so that is works with
+	 * both monotonically increasing and decreasing
+	 * pstate values
+	 */
+	return abs(pstate - idx_to_pstate(powernv_pstate_info.max));
+}
+
 static inline void reset_gpstates(struct cpufreq_policy *policy)
 {
 	struct global_pstate_info *gpstates = policy->driver_data;
 
-	gpstates->highest_lpstate = 0;
+	gpstates->highest_lpstate_idx = 0;
 	gpstates->elapsed_time = 0;
 	gpstates->last_sampled_time = 0;
-	gpstates->last_lpstate = 0;
-	gpstates->last_gpstate = 0;
+	gpstates->last_lpstate_idx = 0;
+	gpstates->last_gpstate_idx = 0;
 }
 
 /*
@@ -156,9 +176,10 @@ static inline void reset_gpstates(struct cpufreq_policy *policy)
 static int init_powernv_pstates(void)
 {
 	struct device_node *power_mgt;
-	int i, pstate_min, pstate_max, pstate_nominal, nr_pstates = 0;
+	int i, nr_pstates = 0;
 	const __be32 *pstate_ids, *pstate_freqs;
 	u32 len_ids, len_freqs;
+	u32 pstate_min, pstate_max, pstate_nominal;
 
 	power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
 	if (!power_mgt) {
@@ -208,6 +229,7 @@ static int init_powernv_pstates(void)
 		return -ENODEV;
 	}
 
+	powernv_pstate_info.nr_pstates = nr_pstates;
 	pr_debug("NR PStates %d\n", nr_pstates);
 	for (i = 0; i < nr_pstates; i++) {
 		u32 id = be32_to_cpu(pstate_ids[i]);
@@ -216,15 +238,17 @@ static int init_powernv_pstates(void)
 		pr_debug("PState id %d freq %d MHz\n", id, freq);
 		powernv_freqs[i].frequency = freq * 1000; /* kHz */
 		powernv_freqs[i].driver_data = id;
+
+		if (id == pstate_max)
+			powernv_pstate_info.max = i;
+		else if (id == pstate_nominal)
+			powernv_pstate_info.nominal = i;
+		else if (id == pstate_min)
+			powernv_pstate_info.min = i;
 	}
+
 	/* End of list marker entry */
 	powernv_freqs[i].frequency = CPUFREQ_TABLE_END;
-
-	powernv_pstate_info.min = pstate_min;
-	powernv_pstate_info.max = pstate_max;
-	powernv_pstate_info.nominal = pstate_nominal;
-	powernv_pstate_info.nr_pstates = nr_pstates;
-
 	return 0;
 }
 
@@ -233,12 +257,12 @@ static unsigned int pstate_id_to_freq(int pstate_id)
 {
 	int i;
 
-	i = powernv_pstate_info.max - pstate_id;
+	i = pstate_to_idx(pstate_id);
 	if (i >= powernv_pstate_info.nr_pstates || i < 0) {
 		pr_warn("PState id %d outside of PState table, "
 			"reporting nominal id %d instead\n",
-			pstate_id, powernv_pstate_info.nominal);
-		i = powernv_pstate_info.max - powernv_pstate_info.nominal;
+			pstate_id, idx_to_pstate(powernv_pstate_info.nominal));
+		i = powernv_pstate_info.nominal;
 	}
 
 	return powernv_freqs[i].frequency;
@@ -252,7 +276,7 @@ static ssize_t cpuinfo_nominal_freq_show(struct cpufreq_policy *policy,
 					char *buf)
 {
 	return sprintf(buf, "%u\n",
-		pstate_id_to_freq(powernv_pstate_info.nominal));
+		powernv_freqs[powernv_pstate_info.nominal].frequency);
 }
 
 struct freq_attr cpufreq_freq_attr_cpuinfo_nominal_freq =
@@ -426,7 +450,7 @@ static void set_pstate(void *data)
  */
 static inline unsigned int get_nominal_index(void)
 {
-	return powernv_pstate_info.max - powernv_pstate_info.nominal;
+	return powernv_pstate_info.nominal;
 }
 
 static void powernv_cpufreq_throttle_check(void *data)
@@ -435,20 +459,22 @@ static void powernv_cpufreq_throttle_check(void *data)
 	unsigned int cpu = smp_processor_id();
 	unsigned long pmsr;
 	int pmsr_pmax;
+	unsigned int pmsr_pmax_idx;
 
 	pmsr = get_pmspr(SPRN_PMSR);
 	chip = this_cpu_read(chip_info);
 
 	/* Check for Pmax Capping */
 	pmsr_pmax = (s8)PMSR_MAX(pmsr);
-	if (pmsr_pmax != powernv_pstate_info.max) {
+	pmsr_pmax_idx = pstate_to_idx(pmsr_pmax);
+	if (pmsr_pmax_idx != powernv_pstate_info.max) {
 		if (chip->throttled)
 			goto next;
 		chip->throttled = true;
-		if (pmsr_pmax < powernv_pstate_info.nominal) {
-			pr_warn_once("CPU %d on Chip %u has Pmax reduced below nominal frequency (%d < %d)\n",
+		if (pmsr_pmax_idx > powernv_pstate_info.nominal) {
+			pr_warn_once("CPU %d on Chip %u has Pmax(%d) reduced below nominal frequency(%d)\n",
 				     cpu, chip->id, pmsr_pmax,
-				     powernv_pstate_info.nominal);
+				     idx_to_pstate(powernv_pstate_info.nominal));
 			chip->throttle_sub_turbo++;
 		} else {
 			chip->throttle_turbo++;
@@ -484,34 +510,35 @@ next:
 
 /**
  * calc_global_pstate - Calculate global pstate
- * @elapsed_time:	Elapsed time in milliseconds
- * @local_pstate:	New local pstate
- * @highest_lpstate:	pstate from which its ramping down
+ * @elapsed_time:		Elapsed time in milliseconds
+ * @local_pstate_idx:		New local pstate
+ * @highest_lpstate_idx:	pstate from which its ramping down
  *
  * Finds the appropriate global pstate based on the pstate from which its
  * ramping down and the time elapsed in ramping down. It follows a quadratic
  * equation which ensures that it reaches ramping down to pmin in 5sec.
  */
 static inline int calc_global_pstate(unsigned int elapsed_time,
-				     int highest_lpstate, int local_pstate)
+				     int highest_lpstate_idx,
+				     int local_pstate_idx)
 {
-	int pstate_diff;
+	int index_diff;
 
 	/*
 	 * Using ramp_down_percent we get the percentage of rampdown
 	 * that we are expecting to be dropping. Difference between
-	 * highest_lpstate and powernv_pstate_info.min will give a absolute
+	 * highest_lpstate_idx and powernv_pstate_info.min will give a absolute
 	 * number of how many pstates we will drop eventually by the end of
 	 * 5 seconds, then just scale it get the number pstates to be dropped.
 	 */
-	pstate_diff =  ((int)ramp_down_percent(elapsed_time) *
-			(highest_lpstate - powernv_pstate_info.min)) / 100;
+	index_diff =  ((int)ramp_down_percent(elapsed_time) *
+			(powernv_pstate_info.min - highest_lpstate_idx)) / 100;
 
 	/* Ensure that global pstate is >= to local pstate */
-	if (highest_lpstate - pstate_diff < local_pstate)
-		return local_pstate;
+	if (highest_lpstate_idx + index_diff >= local_pstate_idx)
+		return local_pstate_idx;
 	else
-		return highest_lpstate - pstate_diff;
+		return highest_lpstate_idx + index_diff;
 }
 
 static inline void  queue_gpstate_timer(struct global_pstate_info *gpstates)
@@ -547,7 +574,7 @@ void gpstate_timer_handler(unsigned long data)
 {
 	struct cpufreq_policy *policy = (struct cpufreq_policy *)data;
 	struct global_pstate_info *gpstates = policy->driver_data;
-	int gpstate_id;
+	int gpstate_idx;
 	unsigned int time_diff = jiffies_to_msecs(jiffies)
 					- gpstates->last_sampled_time;
 	struct powernv_smp_call_data freq_data;
@@ -557,29 +584,29 @@ void gpstate_timer_handler(unsigned long data)
 
 	gpstates->last_sampled_time += time_diff;
 	gpstates->elapsed_time += time_diff;
-	freq_data.pstate_id = gpstates->last_lpstate;
+	freq_data.pstate_id = idx_to_pstate(gpstates->last_lpstate_idx);
 
-	if ((gpstates->last_gpstate == freq_data.pstate_id) ||
+	if ((gpstates->last_gpstate_idx == gpstates->last_lpstate_idx) ||
 	    (gpstates->elapsed_time > MAX_RAMP_DOWN_TIME)) {
-		gpstate_id = freq_data.pstate_id;
+		gpstate_idx = pstate_to_idx(freq_data.pstate_id);
 		reset_gpstates(policy);
-		gpstates->highest_lpstate = freq_data.pstate_id;
+		gpstates->highest_lpstate_idx = gpstate_idx;
 	} else {
-		gpstate_id = calc_global_pstate(gpstates->elapsed_time,
-						gpstates->highest_lpstate,
-						freq_data.pstate_id);
+		gpstate_idx = calc_global_pstate(gpstates->elapsed_time,
+						 gpstates->highest_lpstate_idx,
+						 freq_data.pstate_id);
 	}
 
 	/*
 	 * If local pstate is equal to global pstate, rampdown is over
 	 * So timer is not required to be queued.
 	 */
-	if (gpstate_id != freq_data.pstate_id)
+	if (gpstate_idx != gpstates->last_lpstate_idx)
 		queue_gpstate_timer(gpstates);
 
-	freq_data.gpstate_id = gpstate_id;
-	gpstates->last_gpstate = freq_data.gpstate_id;
-	gpstates->last_lpstate = freq_data.pstate_id;
+	freq_data.gpstate_id = idx_to_pstate(gpstate_idx);
+	gpstates->last_gpstate_idx = pstate_to_idx(freq_data.gpstate_id);
+	gpstates->last_lpstate_idx = pstate_to_idx(freq_data.pstate_id);
 
 	spin_unlock(&gpstates->gpstate_lock);
 
@@ -596,7 +623,7 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
 					unsigned int new_index)
 {
 	struct powernv_smp_call_data freq_data;
-	unsigned int cur_msec, gpstate_id;
+	unsigned int cur_msec, gpstate_idx;
 	struct global_pstate_info *gpstates = policy->driver_data;
 
 	if (unlikely(rebooting) && new_index != get_nominal_index())
@@ -608,15 +635,15 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
 	cur_msec = jiffies_to_msecs(get_jiffies_64());
 
 	spin_lock(&gpstates->gpstate_lock);
-	freq_data.pstate_id = powernv_freqs[new_index].driver_data;
+	freq_data.pstate_id = idx_to_pstate(new_index);
 
 	if (!gpstates->last_sampled_time) {
-		gpstate_id = freq_data.pstate_id;
-		gpstates->highest_lpstate = freq_data.pstate_id;
+		gpstate_idx = new_index;
+		gpstates->highest_lpstate_idx = new_index;
 		goto gpstates_done;
 	}
 
-	if (gpstates->last_gpstate > freq_data.pstate_id) {
+	if (gpstates->last_gpstate_idx < new_index) {
 		gpstates->elapsed_time += cur_msec -
 						 gpstates->last_sampled_time;
 
@@ -627,34 +654,34 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
 		 */
 		if (gpstates->elapsed_time > MAX_RAMP_DOWN_TIME) {
 			reset_gpstates(policy);
-			gpstates->highest_lpstate = freq_data.pstate_id;
-			gpstate_id = freq_data.pstate_id;
+			gpstates->highest_lpstate_idx = new_index;
+			gpstate_idx = new_index;
 		} else {
 		/* Elaspsed_time is less than 5 seconds, continue to rampdown */
-			gpstate_id = calc_global_pstate(gpstates->elapsed_time,
-							gpstates->highest_lpstate,
-							freq_data.pstate_id);
+			gpstate_idx = calc_global_pstate(gpstates->elapsed_time,
+							 gpstates->highest_lpstate_idx,
+							 new_index);
 		}
 	} else {
 		reset_gpstates(policy);
-		gpstates->highest_lpstate = freq_data.pstate_id;
-		gpstate_id = freq_data.pstate_id;
+		gpstates->highest_lpstate_idx = new_index;
+		gpstate_idx = new_index;
 	}
 
 	/*
 	 * If local pstate is equal to global pstate, rampdown is over
 	 * So timer is not required to be queued.
 	 */
-	if (gpstate_id != freq_data.pstate_id)
+	if (gpstate_idx != new_index)
 		queue_gpstate_timer(gpstates);
 	else
 		del_timer_sync(&gpstates->timer);
 
 gpstates_done:
-	freq_data.gpstate_id = gpstate_id;
+	freq_data.gpstate_id = idx_to_pstate(gpstate_idx);
 	gpstates->last_sampled_time = cur_msec;
-	gpstates->last_gpstate = freq_data.gpstate_id;
-	gpstates->last_lpstate = freq_data.pstate_id;
+	gpstates->last_gpstate_idx = gpstate_idx;
+	gpstates->last_lpstate_idx = new_index;
 
 	spin_unlock(&gpstates->gpstate_lock);
 
@@ -847,8 +874,8 @@ static void powernv_cpufreq_stop_cpu(struct cpufreq_policy *policy)
 	struct powernv_smp_call_data freq_data;
 	struct global_pstate_info *gpstates = policy->driver_data;
 
-	freq_data.pstate_id = powernv_pstate_info.min;
-	freq_data.gpstate_id = powernv_pstate_info.min;
+	freq_data.pstate_id = idx_to_pstate(powernv_pstate_info.min);
+	freq_data.gpstate_id = idx_to_pstate(powernv_pstate_info.min);
 	smp_call_function_single(policy->cpu, set_pstate, &freq_data, 1);
 	del_timer_sync(&gpstates->timer);
 }
-- 
2.5.5