From e2f74f355e9e2914483db10c05d70e69e0b7ae04 Mon Sep 17 00:00:00 2001 From: Thomas Renninger Date: Thu, 19 Nov 2009 12:31:01 +0100 Subject: [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 CC: Len Brown CC: davej@codemonkey.org.uk CC: linux@dominikbrodowski.net Signed-off-by: Thomas Renninger Signed-off-by: Dave Jones --- drivers/cpufreq/cpufreq.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'drivers/cpufreq') diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 5b9b1c8..f20668c 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -647,6 +647,21 @@ static ssize_t show_scaling_setspeed(struct cpufreq_policy *policy, char *buf) return policy->governor->show_setspeed(policy, buf); } +/** + * show_scaling_driver - show the current cpufreq HW/BIOS limitation + */ +static ssize_t show_bios_limit(struct cpufreq_policy *policy, char *buf) +{ + unsigned int limit; + int ret; + if (cpufreq_driver->bios_limit) { + ret = cpufreq_driver->bios_limit(policy->cpu, &limit); + if (!ret) + return sprintf(buf, "%u\n", limit); + } + return sprintf(buf, "%u\n", policy->cpuinfo.max_freq); +} + #define define_one_ro(_name) \ static struct freq_attr _name = \ __ATTR(_name, 0444, show_##_name, NULL) @@ -666,6 +681,7 @@ define_one_ro(cpuinfo_transition_latency); define_one_ro(scaling_available_governors); define_one_ro(scaling_driver); define_one_ro(scaling_cur_freq); +define_one_ro(bios_limit); define_one_ro(related_cpus); define_one_ro(affected_cpus); define_one_rw(scaling_min_freq); @@ -905,6 +921,11 @@ static int cpufreq_add_dev_interface(unsigned int cpu, if (ret) goto err_out_kobj_put; } + if (cpufreq_driver->bios_limit) { + ret = sysfs_create_file(&policy->kobj, &bios_limit.attr); + if (ret) + goto err_out_kobj_put; + } spin_lock_irqsave(&cpufreq_driver_lock, flags); for_each_cpu(j, policy->cpus) { -- cgit v1.1