path: root/include
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authorThomas Renninger <trenn@suse.de>2009-11-19 12:31:01 +0100
committerDave Jones <davej@redhat.com>2009-11-24 13:33:34 -0500
commite2f74f355e9e2914483db10c05d70e69e0b7ae04 (patch)
treee17cae217151627c2c95aeeb2a43baf96d49ac91 /include
parentcf3289d0e701b2f59123bf653c12722a7e32aedb (diff)
[ACPI/CPUFREQ] Introduce bios_limit per cpu cpufreq sysfs interface
This interface is mainly intended (and implemented) for ACPI _PPC BIOS frequency limitations, but other cpufreq drivers can also use it for similar use-cases. Why is this needed: Currently it's not obvious why cpufreq got limited. People see cpufreq/scaling_max_freq reduced, but this could have happened by: - any userspace prog writing to scaling_max_freq - thermal limitations - hardware (_PPC in ACPI case) limitiations Therefore export bios_limit (in kHz) to: - Point the user that it's the BIOS (broken or intended) which limits frequency - Export it as a sysfs interface for userspace progs. While this was a rarely used feature on laptops, there will appear more and more server implemenations providing "Green IT" features like allowing the service processor to limit the frequency. People want to know about HW/BIOS frequency limitations. All ACPI P-state driven cpufreq drivers are covered with this patch: - powernow-k8 - powernow-k7 - acpi-cpufreq Tested with a patched DSDT which limits the first two cores (_PPC returns 1) via _PPC, exposed by bios_limit: # echo 2200000 >cpu2/cpufreq/scaling_max_freq # cat cpu*/cpufreq/scaling_max_freq 2600000 2600000 2200000 2200000 # #scaling_max_freq shows general user/thermal/BIOS limitations # cat cpu*/cpufreq/bios_limit 2600000 2600000 2800000 2800000 # #bios_limit only shows the HW/BIOS limitation CC: Pallipadi Venkatesh <venkatesh.pallipadi@intel.com> CC: Len Brown <lenb@kernel.org> CC: davej@codemonkey.org.uk CC: linux@dominikbrodowski.net Signed-off-by: Thomas Renninger <trenn@suse.de> Signed-off-by: Dave Jones <davej@redhat.com>
Diffstat (limited to 'include')
2 files changed, 7 insertions, 0 deletions
diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index 740ac3ad8fd..8b668ead6d6 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -295,6 +295,7 @@ static inline void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx
void acpi_processor_ppc_init(void);
void acpi_processor_ppc_exit(void);
int acpi_processor_ppc_has_changed(struct acpi_processor *pr);
+extern int acpi_processor_get_bios_limit(int cpu, unsigned int *limit);
static inline void acpi_processor_ppc_init(void)
@@ -316,6 +317,11 @@ static inline int acpi_processor_ppc_has_changed(struct acpi_processor *pr)
return 0;
+static inline int acpi_processor_get_bios_limit(int cpu, unsigned int *limit)
+ return -ENODEV;
#endif /* CONFIG_CPU_FREQ */
/* in processor_throttling.c */
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 79a2340d83c..4de02b10007 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -232,6 +232,7 @@ struct cpufreq_driver {
/* optional */
unsigned int (*getavg) (struct cpufreq_policy *policy,
unsigned int cpu);
+ int (*bios_limit) (int cpu, unsigned int *limit);
int (*exit) (struct cpufreq_policy *policy);
int (*suspend) (struct cpufreq_policy *policy, pm_message_t pmsg);