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    Subject[PATCH v2 18/18] cpufreq: scmi: add support for fast frequency switching
    Date
    The cpufreq core provides option for drivers to implement fast_switch
    callback which is invoked for frequency switching from interrupt context.

    This patch adds support for fast_switch callback in SCMI cpufreq driver
    by making use of polling based SCMI transfer. It also sets the flag
    fast_switch_possible.

    Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
    Cc: Viresh Kumar <viresh.kumar@linaro.org>
    Cc: linux-pm@vger.kernel.org
    Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
    ---
    drivers/cpufreq/scmi-cpufreq.c | 16 ++++++++++++++++
    1 file changed, 16 insertions(+)

    diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
    index 034359cafea5..cb1084cb1ef1 100644
    --- a/drivers/cpufreq/scmi-cpufreq.c
    +++ b/drivers/cpufreq/scmi-cpufreq.c
    @@ -61,6 +61,19 @@ scmi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
    return perf_ops->freq_set(priv->handle, priv->domain_id, freq, false);
    }

    +static unsigned int scmi_cpufreq_fast_switch(struct cpufreq_policy *policy,
    + unsigned int target_freq)
    +{
    + struct scmi_data *priv = policy->driver_data;
    + struct scmi_perf_ops *perf_ops = priv->handle->perf_ops;
    +
    + if (!perf_ops->freq_set(priv->handle, priv->domain_id,
    + target_freq * 1000, true))
    + return target_freq;
    +
    + return CPUFREQ_ENTRY_INVALID;
    +}
    +
    static int
    scmi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
    {
    @@ -164,6 +177,7 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)

    policy->cpuinfo.transition_latency = latency;

    + policy->fast_switch_possible = true;
    return 0;

    out_free_cpufreq_table:
    @@ -180,6 +194,7 @@ static int scmi_cpufreq_exit(struct cpufreq_policy *policy)
    {
    struct scmi_data *priv = policy->driver_data;

    + policy->fast_switch_possible = false;
    cpufreq_cooling_unregister(priv->cdev);
    dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
    dev_pm_opp_cpumask_remove_table(policy->related_cpus);
    @@ -228,6 +243,7 @@ static struct cpufreq_driver scmi_cpufreq_driver = {
    .init = scmi_cpufreq_init,
    .exit = scmi_cpufreq_exit,
    .ready = scmi_cpufreq_ready,
    + .fast_switch = scmi_cpufreq_fast_switch,
    };

    static int scmi_cpufreq_probe(struct platform_device *pdev)
    --
    2.7.4
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