[PATCH][RFC] ACPI: add "processor.broadcast_ppc" hook to broadcast _PPC to all online CPUs

[Chen Yu]

On Dell Inc. XPS13 9333, the BIOS changes the value of
MSR_IA32_MISC_ENABLE_TURBO_DISABLE at runtime (e.g., when
the power source changes), the maximum frequency of the
CPU is not updated accordingly. This is due to the policy's
cpuinfo.max is not updated when _PPC notifier fires.

Fix this problem by updating the policy's cpuinfo.max
and broadcast the _PPC notifier to all online CPUs.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=200759
Reported-and-tested-by: Gabriele Mazzotta <gabriele.mzt@xxxxxxxxx>
Originally-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
---
 drivers/acpi/processor_perflib.c | 16 ++++++++++++++--
 drivers/cpufreq/cpufreq.c        |  2 ++
 drivers/cpufreq/intel_pstate.c   | 15 ++++++++++++++-
 3 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index a303fd0e108c..737dbf5aa7f7 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -63,6 +63,10 @@ module_param(ignore_ppc, int, 0644);
 MODULE_PARM_DESC(ignore_ppc, "If the frequency of your machine gets wrongly" \
 		 "limited by BIOS, this should help");
 
+static int broadcast_ppc;
+module_param(broadcast_ppc, int, 0644);
+MODULE_PARM_DESC(broadcast_ppc, "Broadcast the ppc to all online CPUs");
+
 #define PPC_REGISTERED   1
 #define PPC_IN_USE       2
 
@@ -180,8 +184,16 @@ void acpi_processor_ppc_has_changed(struct acpi_processor *pr, int event_flag)
 		else
 			acpi_processor_ppc_ost(pr->handle, 0);
 	}
-	if (ret >= 0)
-		cpufreq_update_policy(pr->id);
+	if (ret >= 0) {
+		if (broadcast_ppc) {
+			int cpu;
+
+			for_each_possible_cpu(cpu)
+				cpufreq_update_policy(cpu);
+		} else {
+			cpufreq_update_policy(pr->id);
+		}
+	}
 }
 
 int acpi_processor_get_bios_limit(int cpu, unsigned int *limit)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index e35a886e00bc..95e08816b512 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2237,6 +2237,8 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
 
 	policy->min = new_policy->min;
 	policy->max = new_policy->max;
+	policy->cpuinfo.max_freq = new_policy->cpuinfo.max_freq;
+	policy->cpuinfo.min_freq = new_policy->cpuinfo.min_freq;
 	trace_cpu_frequency_limits(policy);
 
 	policy->cached_target_freq = UINT_MAX;
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index dd66decf2087..e1881313c396 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2081,11 +2081,24 @@ static void intel_pstate_adjust_policy_max(struct cpufreq_policy *policy,
 
 static int intel_pstate_verify_policy(struct cpufreq_policy *policy)
 {
+	int max_freq;
 	struct cpudata *cpu = all_cpu_data[policy->cpu];
 
 	update_turbo_state();
+	max_freq = intel_pstate_get_max_freq(cpu);
+
+	if (acpi_ppc && policy->max == policy->cpuinfo.max_freq &&
+	    max_freq != policy->cpuinfo.max_freq) {
+		/*
+		 * System was not running under any constraints, but the
+		 * current max possible frequency is changed. So reset
+		 * policy limits.
+		 */
+		policy->cpuinfo.max_freq = policy->max = max_freq;
+	}
+
 	cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
-				     intel_pstate_get_max_freq(cpu));
+				     max_freq);
 
 	if (policy->policy != CPUFREQ_POLICY_POWERSAVE &&
 	    policy->policy != CPUFREQ_POLICY_PERFORMANCE)
-- 
2.17.1