[Patch] cpufreq: tegra194: add online/offline hooks

[Sumit Gupta <sumitg@nvidia.com>]

Implement the light-weight tear down and bring up helpers to reduce the
amount of work to do on CPU offline/online operation.
This change helps to make the hotplugging paths much faster.

Suggested-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
Link: https://lore.kernel.org/lkml/20230816033402.3abmugb5goypvllm@vireshk-i7/
---
 drivers/cpufreq/tegra194-cpufreq.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
index 66a9c23544db..09582696b83d 100644
--- a/drivers/cpufreq/tegra194-cpufreq.c
+++ b/drivers/cpufreq/tegra194-cpufreq.c
@@ -510,6 +510,21 @@ static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
 	return 0;
 }
 
+static int tegra194_cpufreq_online(struct cpufreq_policy *policy)
+{
+	/* We did light-weight tear down earlier, nothing to do here */
+	return 0;
+}
+
+static int tegra194_cpufreq_offline(struct cpufreq_policy *policy)
+{
+	/*
+	 * Preserve policy->driver_data and don't free resources on light-weight
+	 * tear down.
+	 */
+	return 0;
+}
+
 static int tegra194_cpufreq_exit(struct cpufreq_policy *policy)
 {
 	struct device *cpu_dev = get_cpu_device(policy->cpu);
@@ -548,6 +563,8 @@ static struct cpufreq_driver tegra194_cpufreq_driver = {
 	.get = tegra194_get_speed,
 	.init = tegra194_cpufreq_init,
 	.exit = tegra194_cpufreq_exit,
+	.online = tegra194_cpufreq_online,
+	.offline = tegra194_cpufreq_offline,
 	.attr = cpufreq_generic_attr,
 };
 
-- 
2.17.1