linux-kernel - [PATCH 4/4] base/drivers/topology: Default dmpis-mhz if they are not set in DT

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Message-Id: <1540830201-2947-4-git-send-email-daniel.lezcano@linaro.org>
Date:   Mon, 29 Oct 2018 17:23:20 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     rjw@...ysocki.net
Cc:     vincent.guittot@...aro.org, linux-kernel@...r.kernel.org,
        Chris Redpath <chris.redpath@...aro.org>,
        Quentin Perret <quentin.perret@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Nicolas Dechesne <nicolas.dechesne@...aro.org>,
        Niklas Cassel <niklas.cassel@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCH 4/4] base/drivers/topology: Default dmpis-mhz if they are not set in DT

In the case of assymetric SoC with the same micro-architecture, we
have a group of CPUs with smaller OPPs than the other group. One
example is the 96boards dragonboard 820c. There is no dmips/MHz
difference between both groups, so no need to specify the values in
the DT. Unfortunately, without these defined, there is no scaling
capacity comutation triggered, so we need to write
'capacity-dmips-mhz' for each CPU with the same value in order to
force the scaled capacity computation.

Fix this by setting a default capacity to SCHED_CAPACITY_SCALE, if no
'capacity-dmips-mhz' is defined in the DT.

This was tested on db820c:
 - specified values in the DT (correct results)
 - partial values defined in the DT (error + fallback to defaults)
 - no specified values in the DT (correct results)

correct results are:
  cat /sys/devices/system/cpu/cpu*/cpu_capacity
   758
   758
  1024
  1024

  ... respectively for CPU0, CPU1, CPU2 and CPU3.

That reflects the capacity for the max frequencies 1593600 and 2150400.

Cc: Chris Redpath <chris.redpath@...aro.org>
Cc: Quentin Perret <quentin.perret@...aro.org>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Amit Kucheria <amit.kucheria@...aro.org>
Cc: Nicolas Dechesne <nicolas.dechesne@...aro.org>
Cc: Niklas Cassel <niklas.cassel@...aro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/base/arch_topology.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 7311641..7d594a6 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -205,6 +205,21 @@ static struct notifier_block init_cpu_capacity_notifier = {
 	.notifier_call = init_cpu_capacity_callback,
 };
 
+static int topology_set_default_capacity(void)
+{
+	int cpu;
+
+	raw_capacity = kzalloc(num_possible_cpus() * sizeof(*raw_capacity),
+			       GFP_KERNEL);
+	if (!raw_capacity)
+		return -ENOMEM;
+
+	for_each_possible_cpu(cpu)
+		raw_capacity[cpu] = SCHED_CAPACITY_SCALE;
+
+	return 0;
+}
+
 static int __init register_cpufreq_notifier(void)
 {
 	int ret;
@@ -214,9 +229,19 @@ static int __init register_cpufreq_notifier(void)
 	 * until we have the necessary code to parse the cpu capacity, so
 	 * skip registering cpufreq notifier.
 	 */
-	if (!acpi_disabled || !raw_capacity)
+	if (!acpi_disabled)
 		return -EINVAL;
 
+	if (!raw_capacity) {
+
+		pr_info("cpu_capacity: No capacity defined in DT, set default "
+		       "values to %ld\n", SCHED_CAPACITY_SCALE);
+
+		ret = topology_set_default_capacity();
+		if (ret)
+			return ret;
+	}
+
 	if (!alloc_cpumask_var(&cpus_to_visit, GFP_KERNEL)) {
 		pr_err("cpu_capacity: failed to allocate memory for cpus_to_visit\n");
 		return -ENOMEM;
-- 
2.7.4