powercap / RAPL: further relax energy counter checks

Energy counters may roll slowly for some RAPL domains, checking all
of them can be time consuming and takes unpredictable amount of time.
Therefore, we relax the sanity check by only checking availability of the
MSRs and non-zero value of the energy status counters. It has been shown
sufficient for all the platforms tested to filter out inactive domains.

Signed-off-by: Jacob Pan <[e-mail]>
Acked-by: Durgadoss R <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/powercap/intel_rapl.c

···
 static int rapl_check_domain(int cpu, int domain)
 {
 	unsigned msr;
-	u64 val1, val2 = 0;
-	int retry = 0;
+	u64 val = 0;
 
 	switch (domain) {
 	case RAPL_DOMAIN_PACKAGE:
···
 		pr_err("invalid domain id %d\n", domain);
 		return -EINVAL;
 	}
-	if (rdmsrl_safe_on_cpu(cpu, msr, &val1))
+	/* make sure domain counters are available and contains non-zero
+	 * values, otherwise skip it.
+	 */
+	if (rdmsrl_safe_on_cpu(cpu, msr, &val) || !val)
 		return -ENODEV;
 
-	/* PP1/uncore/graphics domain may not be active at the time of
-	 * driver loading. So skip further checks.
-	 */
-	if (domain == RAPL_DOMAIN_PP1)
-		return 0;
-	/* energy counters roll slowly on some domains */
-	while (++retry < 10) {
-		usleep_range(10000, 15000);
-		rdmsrl_safe_on_cpu(cpu, msr, &val2);
-		if ((val1 & ENERGY_STATUS_MASK) != (val2 & ENERGY_STATUS_MASK))
-			return 0;
-	}
-	/* if energy counter does not change, report as bad domain */
-	pr_info("domain %s energy ctr %llu:%llu not working, skip\n",
-		rapl_domain_names[domain], val1, val2);
-
-	return -ENODEV;
+	return 0;
 }
 
 /* Detect active and valid domains for the given CPU, caller must
···
 		/* use physical package id to read counters */
 		if (!rapl_check_domain(cpu, i))
 			rp->domain_map |= 1 << i;
+		else
+			pr_warn("RAPL domain %s detection failed\n",
+				rapl_domain_names[i]);
 	}
 	rp->nr_domains = bitmap_weight(&rp->domain_map,	RAPL_DOMAIN_MAX);
 	if (!rp->nr_domains) {