linux-kernel - [PATCH 6/8] cppc_cpufreq: clarify support for coordination types

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Date:   Thu,  5 Nov 2020 12:55:22 +0000
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     rjw@...ysocki.net, viresh.kumar@...aro.org, lenb@...nel.org,
        sudeep.holla@....com
Cc:     morten.rasmussen@....com, jeremy.linton@....com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        ionela.voinescu@....com
Subject: [PATCH 6/8] cppc_cpufreq: clarify support for coordination types

The previous coordination type handling in the cppc_cpufreq init code
created some confusion: the comment mentioned "Support only SW_ANY for
now" while only the SW_ALL/ALL case resulted in a failure. The other
coordination types (HW_ALL/HW, NONE) were silently supported.

Clarify support for coordination types while describing in comments the
intended behavior.

Signed-off-by: Ionela Voinescu <ionela.voinescu@....com>
Cc: Rafael J. Wysocki <rjw@...ysocki.net>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/cppc_cpufreq.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index fd2daeb59b49..60ac7f8049b5 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -363,11 +363,22 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	policy->transition_delay_us = cppc_cpufreq_get_transition_delay_us(cpu);
 	policy->shared_type = domain->shared_type;
 
-	if (policy->shared_type == CPUFREQ_SHARED_TYPE_ANY) {
+	switch (policy->shared_type) {
+	case CPUFREQ_SHARED_TYPE_HW:
+	case CPUFREQ_SHARED_TYPE_NONE:
+		/* Nothing to be done - we'll have a policy for each CPU */
+		break;
+	case CPUFREQ_SHARED_TYPE_ANY:
+		/*
+		 * All CPUs in the domain will share a policy and all cpufreq
+		 * operations will use a single cppc_cpudata structure stored
+		 * in policy->driver_data.
+		 */
 		cpumask_copy(policy->cpus, domain->shared_cpu_map);
-	} else if (policy->shared_type == CPUFREQ_SHARED_TYPE_ALL) {
-		/* Support only SW_ANY for now. */
-		pr_debug("Unsupported CPU co-ord type\n");
+		break;
+	default:
+		pr_info("Unsupported cpufreq CPU co-ord type: %d\n",
+			policy->shared_type);
 		return -EFAULT;
 	}
 
-- 
2.17.1