Merge tag 'pm-5.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management fixes from Rafael Wysocki:
 "These fix a crash during resume from hibernation introduced during the
  4.19 cycle, cause the new Performance and Energy Bias Hint (EPB) code
  to be built only if CONFIG_PM is set and add a few missing kerneldoc
  comments.

  Specifics:

   - Fix a crash that occurs when a kernel with 'nosmt' in the command
     line is used to resume the system from hibernation (as the
     "restore" kernel), because memory mapping differences between the
     restore and image kernels cause SMT siblings to be woken up from
     idle states and subsequently they try to fetch instructions from
     incorrect memory locations (Jiri Kosina).

   - Cause the new Performance and Energy Bias Hint (EPB) code to be
     built only if CONFIG_PM is set, because that code is not really
     necessary otherwise (Rafael Wysocki).

   - Add kerneldoc comments to documents some helper functions related
     to system-wide suspend to avoid possible confusion regarding their
     purpose (Rafael Wysocki)"

* tag 'pm-5.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  x86/power: Fix 'nosmt' vs hibernation triple fault during resume
  PM: sleep: Add kerneldoc comments to some functions
  x86: intel_epb: Do not build when CONFIG_PM is unset

2 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 3813fe45effd..fcb1386bb0d4 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -201,10 +201,14 @@ enum cpuhp_smt_control {
 extern enum cpuhp_smt_control cpu_smt_control;
 extern void cpu_smt_disable(bool force);
 extern void cpu_smt_check_topology(void);
+extern int cpuhp_smt_enable(void);
+extern int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval);
 #else
 # define cpu_smt_control		(CPU_SMT_NOT_IMPLEMENTED)
 static inline void cpu_smt_disable(bool force) { }
 static inline void cpu_smt_check_topology(void) { }
+static inline int cpuhp_smt_enable(void) { return 0; }
+static inline int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) { return 0; }
 #endif
 
 /*
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 4a2ffd678887..8594001e8be8 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -227,11 +227,42 @@ static inline void pm_set_resume_via_firmware(void)
 	pm_suspend_global_flags |= PM_SUSPEND_FLAG_FW_RESUME;
 }
 
+/**
+ * pm_suspend_via_firmware - Check if platform firmware will suspend the system.
+ *
+ * To be called during system-wide power management transitions to sleep states
+ * or during the subsequent system-wide transitions back to the working state.
+ *
+ * Return 'true' if the platform firmware is going to be invoked at the end of
+ * the system-wide power management transition (to a sleep state) in progress in
+ * order to complete it, or if the platform firmware has been invoked in order
+ * to complete the last (or preceding) transition of the system to a sleep
+ * state.
+ *
+ * This matters if the caller needs or wants to carry out some special actions
+ * depending on whether or not control will be passed to the platform firmware
+ * subsequently (for example, the device may need to be reset before letting the
+ * platform firmware manipulate it, which is not necessary when the platform
+ * firmware is not going to be invoked) or when such special actions may have
+ * been carried out during the preceding transition of the system to a sleep
+ * state (as they may need to be taken into account).
+ */
 static inline bool pm_suspend_via_firmware(void)
 {
 	return !!(pm_suspend_global_flags & PM_SUSPEND_FLAG_FW_SUSPEND);
 }
 
+/**
+ * pm_resume_via_firmware - Check if platform firmware has woken up the system.
+ *
+ * To be called during system-wide power management transitions from sleep
+ * states.
+ *
+ * Return 'true' if the platform firmware has passed control to the kernel at
+ * the beginning of the system-wide power management transition in progress, so
+ * the event that woke up the system from sleep has been handled by the platform
+ * firmware.
+ */
 static inline bool pm_resume_via_firmware(void)
 {
 	return !!(pm_suspend_global_flags & PM_SUSPEND_FLAG_FW_RESUME);