ACPI: processor: perflib: Fix initial _PPC limit application

If the BIOS sets a _PPC frequency limit upfront, it will fail to take
effect due to a call ordering issue. Namely, freq_qos_update_request()
is called before freq_qos_add_request() for the given request causing
the constraint update to be ignored. The call sequence in question is
as follows:

cpufreq_policy_online()
acpi_cpufreq_cpu_init()
acpi_processor_register_performance()
acpi_processor_get_performance_info()
acpi_processor_get_platform_limit()
freq_qos_update_request(&perflib_req) <- inactive QoS request
blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
CPUFREQ_CREATE_POLICY)
acpi_processor_notifier()
acpi_processor_ppc_init()
freq_qos_add_request(&perflib_req) <- QoS request activation

Address this by adding an acpi_processor_get_platform_limit() call
to acpi_processor_ppc_init(), after the perflib_req activation via
freq_qos_add_request(), which causes the initial _PPC limit to be
picked up as appropriate. However, also ensure that the _PPC limit
will not be picked up in the cases when the cpufreq driver does not
call acpi_processor_register_performance() by adding a pr->performance
check to the related_cpus loop in acpi_processor_ppc_init().

Fixes: d15ce412737a ("ACPI: cpufreq: Switch to QoS requests instead of cpufreq notifier")
Signed-off-by: Jiayi Li <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
[ rjw: Consolidate pr-related checks in acpi_processor_ppc_init() ]
[ rjw: Subject and changelog adjustments ]
Cc: 5.4+ <[e-mail]> # 5.4+: 2d8b39a62a5d ACPI: processor: Avoid NULL pointer dereferences at init time
Cc: 5.4+ <[e-mail]> # 5.4+: 3000ce3c52f8 cpufreq: Use per-policy frequency QoS
Cc: 5.4+ <[e-mail]> # 5.4+: a1bb46c36ce3 ACPI: processor: Add QoS requests for all CPUs
Cc: 5.4+ <[e-mail]> # 5.4+
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/processor_perflib.c

···
 {
 	unsigned int cpu;
 
+	if (ignore_ppc == 1)
+		return;
+
 	for_each_cpu(cpu, policy->related_cpus) {
 		struct acpi_processor *pr = per_cpu(processors, cpu);
 		int ret;
 
-		if (!pr)
+		if (!pr || !pr->performance)
 			continue;
 
 		/*
···
 					   FREQ_QOS_MAX_DEFAULT_VALUE);
 		if (ret < 0)
 			pr_err("Failed to add freq constraint for CPU%d (%d)\n",
+			       cpu, ret);
+
+		ret = acpi_processor_get_platform_limit(pr);
+		if (ret)
+			pr_err("Failed to update freq constraint for CPU%d (%d)\n",
 			       cpu, ret);
 	}
 }