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Commit f331413e authored by Rafael J. Wysocki's avatar Rafael J. Wysocki Committed by Greg Kroah-Hartman
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ACPI: processor: perflib: Avoid updating frequency QoS unnecessarily 



commit 99387b016022c29234c4ebf9abd34358c6e56532 upstream.

Modify acpi_processor_get_platform_limit() to avoid updating its
frequency QoS request when the _PPC return value has not changed
by comparing that value to the previous _PPC return value stored in
the performance_platform_limit field of the struct acpi_processor
corresponding to the given CPU.

While at it, do the _PPC return value check against the state count
earlier, to avoid setting performance_platform_limit to an invalid
value, and make acpi_processor_ppc_init() use FREQ_QOS_MAX_DEFAULT_VALUE
as the "no limit" frequency QoS for consistency.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarHagar Hemdan <hagarhem@amazon.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 511851c8

drivers/acpi/processor_perflib.c

+14 −4
Original line number Diff line number Diff line
@@ -79,13 +79,16 @@ static int acpi_processor_get_platform_limit(struct acpi_processor *pr) 


	index = ppc;



	if (pr->performance_platform_limit == index ||

	    ppc >= pr->performance->state_count)

		return 0;



	pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr->id,

		 index, index ? "is" : "is not");



	pr->performance_platform_limit = index;



	if (ppc >= pr->performance->state_count ||

	    unlikely(!freq_qos_request_active(&pr->perflib_req)))

	if (unlikely(!freq_qos_request_active(&pr->perflib_req)))

		return 0;



	/*
@@ -180,9 +183,16 @@ void acpi_processor_ppc_init(struct cpufreq_policy *policy) 
		if (!pr)

			continue;



		/*

		 * Reset performance_platform_limit in case there is a stale

		 * value in it, so as to make it match the "no limit" QoS value

		 * below.

		 */

		pr->performance_platform_limit = 0;



		ret = freq_qos_add_request(&policy->constraints,

					   &pr->perflib_req,

					   FREQ_QOS_MAX, INT_MAX);

					   &pr->perflib_req, FREQ_QOS_MAX,

					   FREQ_QOS_MAX_DEFAULT_VALUE);

		if (ret < 0)

			pr_err("Failed to add freq constraint for CPU%d (%d)\n",

			       cpu, ret);