linux-kernel - [PATCH 2/8 v2] acpi-cpufreq: Add quirk to disable

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Date:	Tue, 4 Sep 2012 10:28:03 +0200
From:	Andre Przywara <andre.przywara@....com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>, Thomas Renninger <trenn@...e.de>
CC:	Matthew Garret <mjg@...hat.com>, <linux-pm@...r.kernel.org>,
	<cpufreq@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Andre Przywara <andre.przywara@....com>
Subject: [PATCH 2/8 v2] acpi-cpufreq: Add quirk to disable _PSD usage on all AMD CPUs

To workaround some Windows specific behavior, the ACPI _PSD table
on AMD desktop boards advertises all cores as dependent, meaning
that they all can only use the same P-state. acpi-cpufreq strictly
obeys this description, instantiating one CPU only and symlinking
the others. But the hardware can have distinct frequencies for each
core and powernow-k8 did it that way.
So, in order to use the hardware to its full potential and keep the
original powernow-k8 behavior, lets override the _PSD table setting
on AMD hardware.
We use the siblings table, as it matches the current hardware
behavior.

Signed-off-by: Andre Przywara <andre.przywara@....com>
---
 drivers/cpufreq/acpi-cpufreq.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 067a61f..70e7173 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -51,6 +51,8 @@ MODULE_AUTHOR("Paul Diefenbaugh, Dominik Brodowski");
 MODULE_DESCRIPTION("ACPI Processor P-States Driver");
 MODULE_LICENSE("GPL");
 
+#define PFX "acpi-cpufreq: "
+
 enum {
 	UNDEFINED_CAPABLE = 0,
 	SYSTEM_INTEL_MSR_CAPABLE,
@@ -586,6 +588,14 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
 		policy->shared_type = CPUFREQ_SHARED_TYPE_ALL;
 		cpumask_copy(policy->cpus, cpu_core_mask(cpu));
 	}
+
+	if (check_amd_hwpstate_cpu(cpu) && !acpi_pstate_strict) {
+		cpumask_clear(policy->cpus);
+		cpumask_set_cpu(cpu, policy->cpus);
+		cpumask_copy(policy->related_cpus, cpu_sibling_mask(cpu));
+		policy->shared_type = CPUFREQ_SHARED_TYPE_HW;
+		pr_info_once(PFX "overriding BIOS provided _PSD data\n");
+	}
 #endif
 
 	/* capability check */
-- 
1.7.12


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