clk: qcom: clk-cpu-osm: Reduce CPU frequency update rate limit to 500 us

Rate-limiting frequency updates to once every 10 ms has a substantial
impact on performance due to how slowly the frequency tends to ramp with
such a long delay. Reduce the delay to 500 us which is closer to the
actual frequency switch delay in hardware.

Signed-off-by: Danny Lin <danny@kdrag0n.dev>

Author: kdrag0n

drivers/clk/qcom/clk-cpu-osm.c

@@ -43,7 +43,8 @@
 
 #define OSM_INIT_RATE			300000000UL
 #define XO_RATE				19200000UL
-#define RATE_LIMIT_US			10000
+#define MIN_RATE_LIMIT_US		500
+#define MAX_RATE_LIMIT_US		1000
 #define OSM_TABLE_SIZE			40
 #define SINGLE_CORE			1
 #define MAX_CLUSTER_CNT			3
@@ -676,9 +677,9 @@ osm_set_index(struct clk_osm *c, unsigned int index)
 
 	/* The old rate needs time to settle before it can be changed again */
 	delta_us = ktime_us_delta(ktime_get_boottime(), parent->last_update);
-	if (delta_us < RATE_LIMIT_US)
-		usleep_range(RATE_LIMIT_US - delta_us,
-			     (RATE_LIMIT_US + 1000) - delta_us);
+	if (delta_us < MIN_RATE_LIMIT_US)
+		usleep_range(MIN_RATE_LIMIT_US - delta_us,
+			     MAX_RATE_LIMIT_US - delta_us);
 	parent->last_update = ktime_get_boottime();
 
 	clk_set_rate(c->hw.clk, clk_round_rate(c->hw.clk, rate));
@@ -792,7 +793,7 @@ static int osm_cpufreq_cpu_init(struct cpufreq_policy *policy)
 		goto err;
 	}
 
-	policy->cpuinfo.transition_latency = RATE_LIMIT_US;
+	policy->cpuinfo.transition_latency = MIN_RATE_LIMIT_US;
 	policy->driver_data = c;
 	return 0;