5 files changed, 97 insertions, 38 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index eacb2e0397ae..10b8cc1bda8d 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1446,6 +1446,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        disable
                          Do not enable intel_pstate as the default
                          scaling driver for the supported processors
+                       force
+                         Enable intel_pstate on systems that prohibit it by default
+                         in favor of acpi-cpufreq. Forcing the intel_pstate driver
+                         instead of acpi-cpufreq may disable platform features, such
+                         as thermal controls and power capping, that rely on ACPI
+                         P-States information being indicated to OSPM and therefore
+                         should be used with caution. This option does not work with
+                         processors that aren't supported by the intel_pstate driver
+                         or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
                        no_hwp
                          Do not enable hardware P state control (HWP)
                          if available.
diff --git a/MAINTAINERS b/MAINTAINERS
index c8927bc7748e..1c63cfecc6bf 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4869,6 +4869,12 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux.git
 S:      Supported
 F:      drivers/idle/intel_idle.c
 
+INTEL PSTATE DRIVER
+M:      Kristen Carlson Accardi <kristen@linux.intel.com>
+L:      linux-pm@vger.kernel.org
+S:      Supported
+F:      drivers/cpufreq/intel_pstate.c
+
 INTEL FRAMEBUFFER DRIVER (excluding 810 and 815)
 M:      Maik Broemme <mbroemme@plusserver.de>
 L:      linux-fbdev@vger.kernel.org
diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
index 1bbef8e838e7..d24dd614a0bd 100644
--- a/drivers/base/power/opp.c
+++ b/drivers/base/power/opp.c
@@ -84,7 +84,11 @@ struct dev_pm_opp {
  *
  * This is an internal data structure maintaining the link to opps attached to
  * a device. This structure is not meant to be shared to users as it is
- * meant for book keeping and private to OPP library
+ * meant for book keeping and private to OPP library.
+ *
+ * Because the opp structures can be used from both rcu and srcu readers, we
+ * need to wait for the grace period of both of them before freeing any
+ * resources. And so we have used kfree_rcu() from within call_srcu() handlers.
  */
 struct device_opp {
         struct list_head node;
@@ -382,12 +386,34 @@ struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_floor);
 
+static struct device_opp *add_device_opp(struct device *dev)
+{
+        struct device_opp *dev_opp;
+
+        /*
+         * Allocate a new device OPP table. In the infrequent case where a new
+         * device is needed to be added, we pay this penalty.
+         */
+        dev_opp = kzalloc(sizeof(*dev_opp), GFP_KERNEL);
+        if (!dev_opp)
+                return NULL;
+
+        dev_opp->dev = dev;
+        srcu_init_notifier_head(&dev_opp->srcu_head);
+        INIT_LIST_HEAD(&dev_opp->opp_list);
+
+        /* Secure the device list modification */
+        list_add_rcu(&dev_opp->node, &dev_opp_list);
+        return dev_opp;
+}
+
 static int dev_pm_opp_add_dynamic(struct device *dev, unsigned long freq,
                                   unsigned long u_volt, bool dynamic)
 {
         struct device_opp *dev_opp = NULL;
         struct dev_pm_opp *opp, *new_opp;
         struct list_head *head;
+        int ret;
 
         /* allocate new OPP node */
         new_opp = kzalloc(sizeof(*new_opp), GFP_KERNEL);
@@ -408,27 +434,12 @@ static int dev_pm_opp_add_dynamic(struct device *dev, unsigned long freq,
         /* Check for existing list for 'dev' */
         dev_opp = find_device_opp(dev);
         if (IS_ERR(dev_opp)) {
-                /*
-                 * Allocate a new device OPP table. In the infrequent case
-                 * where a new device is needed to be added, we pay this
-                 * penalty.
-                 */
-                dev_opp = kzalloc(sizeof(struct device_opp), GFP_KERNEL);
+                dev_opp = add_device_opp(dev);
                 if (!dev_opp) {
-                        mutex_unlock(&dev_opp_list_lock);
-                        kfree(new_opp);
-                        dev_warn(dev,
-                                "%s: Unable to create device OPP structure\n",
-                                __func__);
-                        return -ENOMEM;
+                        ret = -ENOMEM;
+                        goto free_opp;
                 }
 
-                dev_opp->dev = dev;
-                srcu_init_notifier_head(&dev_opp->srcu_head);
-                INIT_LIST_HEAD(&dev_opp->opp_list);
-
-                /* Secure the device list modification */
-                list_add_rcu(&dev_opp->node, &dev_opp_list);
                 head = &dev_opp->opp_list;
                 goto list_add;
         }
@@ -447,15 +458,13 @@ static int dev_pm_opp_add_dynamic(struct device *dev, unsigned long freq,
 
         /* Duplicate OPPs ? */
         if (new_opp->rate == opp->rate) {
-                int ret = opp->available && new_opp->u_volt == opp->u_volt ?
+                ret = opp->available && new_opp->u_volt == opp->u_volt ?
                         0 : -EEXIST;
 
                 dev_warn(dev, "%s: duplicate OPPs detected. Existing: freq: %lu, volt: %lu, enabled: %d. New: freq: %lu, volt: %lu, enabled: %d\n",
                          __func__, opp->rate, opp->u_volt, opp->available,
                          new_opp->rate, new_opp->u_volt, new_opp->available);
-                mutex_unlock(&dev_opp_list_lock);
-                kfree(new_opp);
-                return ret;
+                goto free_opp;
         }
 
 list_add:
@@ -469,6 +478,11 @@ list_add:
          */
         srcu_notifier_call_chain(&dev_opp->srcu_head, OPP_EVENT_ADD, new_opp);
         return 0;
+
+free_opp:
+        mutex_unlock(&dev_opp_list_lock);
+        kfree(new_opp);
+        return ret;
 }
 
 /**
@@ -511,10 +525,11 @@ static void kfree_device_rcu(struct rcu_head *head)
 {
         struct device_opp *device_opp = container_of(head, struct device_opp, rcu_head);
 
-        kfree(device_opp);
+        kfree_rcu(device_opp, rcu_head);
 }
 
-void __dev_pm_opp_remove(struct device_opp *dev_opp, struct dev_pm_opp *opp)
+static void __dev_pm_opp_remove(struct device_opp *dev_opp,
+                                struct dev_pm_opp *opp)
 {
         /*
          * Notify the changes in the availability of the operable
@@ -592,7 +607,7 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_remove);
 static int opp_set_availability(struct device *dev, unsigned long freq,
                 bool availability_req)
 {
-        struct device_opp *tmp_dev_opp, *dev_opp = ERR_PTR(-ENODEV);
+        struct device_opp *dev_opp;
         struct dev_pm_opp *new_opp, *tmp_opp, *opp = ERR_PTR(-ENODEV);
         int r = 0;
 
@@ -606,12 +621,7 @@ static int opp_set_availability(struct device *dev, unsigned long freq,
         mutex_lock(&dev_opp_list_lock);
 
         /* Find the device_opp */
-        list_for_each_entry(tmp_dev_opp, &dev_opp_list, node) {
-                if (dev == tmp_dev_opp->dev) {
-                        dev_opp = tmp_dev_opp;
-                        break;
-                }
-        }
+        dev_opp = find_device_opp(dev);
         if (IS_ERR(dev_opp)) {
                 r = PTR_ERR(dev_opp);
                 dev_warn(dev, "%s: Device OPP not found (%d)\n", __func__, r);
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 1405b393c93d..742eefba12c2 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -199,7 +199,14 @@ static signed int pid_calc(struct _pid *pid, int32_t busy)
 
         pid->integral += fp_error;
 
-        /* limit the integral term */
+        /*
+         * We limit the integral here so that it will never
+         * get higher than 30.  This prevents it from becoming
+         * too large an input over long periods of time and allows
+         * it to get factored out sooner.
+         *
+         * The value of 30 was chosen through experimentation.
+         */
         integral_limit = int_tofp(30);
         if (pid->integral > integral_limit)
                 pid->integral = integral_limit;
@@ -616,6 +623,11 @@ static void intel_pstate_get_min_max(struct cpudata *cpu, int *min, int *max)
         if (limits.no_turbo || limits.turbo_disabled)
                 max_perf = cpu->pstate.max_pstate;
 
+        /*
+         * performance can be limited by user through sysfs, by cpufreq
+         * policy, or by cpu specific default values determined through
+         * experimentation.
+         */
         max_perf_adj = fp_toint(mul_fp(int_tofp(max_perf), limits.max_perf));
         *max = clamp_t(int, max_perf_adj,
                         cpu->pstate.min_pstate, cpu->pstate.turbo_pstate);
@@ -717,11 +729,29 @@ static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu)
         u32 duration_us;
         u32 sample_time;
 
+        /*
+         * core_busy is the ratio of actual performance to max
+         * max_pstate is the max non turbo pstate available
+         * current_pstate was the pstate that was requested during
+         *      the last sample period.
+         *
+         * We normalize core_busy, which was our actual percent
+         * performance to what we requested during the last sample
+         * period. The result will be a percentage of busy at a
+         * specified pstate.
+         */
         core_busy = cpu->sample.core_pct_busy;
         max_pstate = int_tofp(cpu->pstate.max_pstate);
         current_pstate = int_tofp(cpu->pstate.current_pstate);
         core_busy = mul_fp(core_busy, div_fp(max_pstate, current_pstate));
 
+        /*
+         * Since we have a deferred timer, it will not fire unless
+         * we are in C0.  So, determine if the actual elapsed time
+         * is significantly greater (3x) than our sample interval.  If it
+         * is, then we were idle for a long enough period of time
+         * to adjust our busyness.
+         */
         sample_time = pid_params.sample_rate_ms  * USEC_PER_MSEC;
         duration_us = (u32) ktime_us_delta(cpu->sample.time,
                                            cpu->last_sample_time);
@@ -948,6 +978,7 @@ static struct cpufreq_driver intel_pstate_driver = {
 
 static int __initdata no_load;
 static int __initdata no_hwp;
+static unsigned int force_load;
 
 static int intel_pstate_msrs_not_valid(void)
 {
@@ -1094,7 +1125,8 @@ static bool intel_pstate_platform_pwr_mgmt_exists(void)
                         case PSS:
                                 return intel_pstate_no_acpi_pss();
                         case PPC:
-                                return intel_pstate_has_acpi_ppc();
+                                return intel_pstate_has_acpi_ppc() &&
+                                        (!force_load);
                         }
         }
 
@@ -1175,6 +1207,8 @@ static int __init intel_pstate_setup(char *str)
                 no_load = 1;
         if (!strcmp(str, "no_hwp"))
                 no_hwp = 1;
+        if (!strcmp(str, "force"))
+                force_load = 1;
         return 0;
 }
 early_param("intel_pstate", intel_pstate_setup);
diff --git a/tools/power/cpupower/utils/cpuidle-info.c b/tools/power/cpupower/utils/cpuidle-info.c
index 458d69b444ad..75e66de7e7a7 100644
--- a/tools/power/cpupower/utils/cpuidle-info.c
+++ b/tools/power/cpupower/utils/cpuidle-info.c
@@ -22,13 +22,13 @@
 
 static void cpuidle_cpu_output(unsigned int cpu, int verbose)
 {
-        int idlestates, idlestate;
+        unsigned int idlestates, idlestate;
         char *tmp;
 
         printf(_ ("Analyzing CPU %d:\n"), cpu);
 
         idlestates = sysfs_get_idlestate_count(cpu);
-        if (idlestates < 1) {
+        if (idlestates == 0) {
                 printf(_("CPU %u: No idle states\n"), cpu);
                 return;
         }
@@ -100,10 +100,10 @@ static void cpuidle_general_output(void)
 static void proc_cpuidle_cpu_output(unsigned int cpu)
 {
         long max_allowed_cstate = 2000000000;
-        int cstate, cstates;
+        unsigned int cstate, cstates;
 
         cstates = sysfs_get_idlestate_count(cpu);
-        if (cstates < 1) {
+        if (cstates == 0) {
                 printf(_("CPU %u: No C-states info\n"), cpu);
                 return;
         }