intel_pstate: Fix user input of min/max to legal policy region

In current code, max_perf_pct might be smaller than min_perf_pct
by improper user input:

$ grep . /sys/devices/system/cpu/intel_pstate/m*_perf_pct
/sys/devices/system/cpu/intel_pstate/max_perf_pct:100
/sys/devices/system/cpu/intel_pstate/min_perf_pct:100

$ echo 80 > /sys/devices/system/cpu/intel_pstate/max_perf_pct

$ grep . /sys/devices/system/cpu/intel_pstate/m*_perf_pct
/sys/devices/system/cpu/intel_pstate/max_perf_pct:80
/sys/devices/system/cpu/intel_pstate/min_perf_pct:100

Fix this problem by 2 steps:
 1. Normalize the user input to [min_policy, max_policy].
 2. Make sure max_perf_pct>=min_perf_pct, suggested by Seiichi Ikarashi.
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Acked-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/intel_pstate.c

@@ -423,6 +423,8 @@ static ssize_t store_max_perf_pct(struct kobject *a, struct attribute *b,
 
 	limits.max_sysfs_pct = clamp_t(int, input, 0 , 100);
 	limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct);
+	limits.max_perf_pct = max(limits.min_policy_pct, limits.max_perf_pct);
+	limits.max_perf_pct = max(limits.min_perf_pct, limits.max_perf_pct);
 	limits.max_perf = div_fp(int_tofp(limits.max_perf_pct), int_tofp(100));
 
 	if (hwp_active)
@@ -442,6 +444,8 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct attribute *b,
 
 	limits.min_sysfs_pct = clamp_t(int, input, 0 , 100);
 	limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct);
+	limits.min_perf_pct = min(limits.max_policy_pct, limits.min_perf_pct);
+	limits.min_perf_pct = min(limits.max_perf_pct, limits.min_perf_pct);
 	limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
 
 	if (hwp_active)
@@ -989,12 +993,19 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
 
 	limits.min_policy_pct = (policy->min * 100) / policy->cpuinfo.max_freq;
 	limits.min_policy_pct = clamp_t(int, limits.min_policy_pct, 0 , 100);
-	limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct);
-	limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
-
 	limits.max_policy_pct = (policy->max * 100) / policy->cpuinfo.max_freq;
 	limits.max_policy_pct = clamp_t(int, limits.max_policy_pct, 0 , 100);
+
+	/* Normalize user input to [min_policy_pct, max_policy_pct] */
+	limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct);
+	limits.min_perf_pct = min(limits.max_policy_pct, limits.min_perf_pct);
 	limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct);
+	limits.max_perf_pct = max(limits.min_policy_pct, limits.max_perf_pct);
+
+	/* Make sure min_perf_pct <= max_perf_pct */
+	limits.min_perf_pct = min(limits.max_perf_pct, limits.min_perf_pct);
+
+	limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
 	limits.max_perf = div_fp(int_tofp(limits.max_perf_pct), int_tofp(100));
 
 	if (hwp_active)