PCI: PM: Avoid skipping bus-level PM on platforms without ACPI

There are platforms that do not call pm_set_suspend_via_firmware(),
so pm_suspend_via_firmware() returns 'false' on them, but the power
states of PCI devices (PCIe ports in particular) are changed as a
result of powering down core platform components during system-wide
suspend.  Thus the pm_suspend_via_firmware() checks in
pci_pm_suspend_noirq() and pci_pm_resume_noirq() introduced by
commit 3e26c5feed2a ("PCI: PM: Skip devices in D0 for suspend-to-
idle") are not sufficient to determine that devices left in D0
during suspend will remain in D0 during resume and so the bus-level
power management can be skipped for them.

For this reason, introduce a new global suspend flag,
PM_SUSPEND_FLAG_NO_PLATFORM, set it for suspend-to-idle only
and replace the pm_suspend_via_firmware() checks mentioned above
with checks against this flag.

Fixes: 3e26c5feed2a ("PCI: PM: Skip devices in D0 for suspend-to-idle")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

3 files changed, 31 insertions, 6 deletions

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 98af9ecd4a90..ca3793002e2f 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -859,7 +859,7 @@ static int pci_pm_suspend_noirq(struct device *dev)
                         pci_dev->bus->self->skip_bus_pm = true;
         }
 
-        if (pci_dev->skip_bus_pm && !pm_suspend_via_firmware()) {
+        if (pci_dev->skip_bus_pm && pm_suspend_no_platform()) {
                 dev_dbg(dev, "PCI PM: Skipped\n");
                 goto Fixup;
         }
@@ -914,10 +914,10 @@ static int pci_pm_resume_noirq(struct device *dev)
         /*
          * In the suspend-to-idle case, devices left in D0 during suspend will
          * stay in D0, so it is not necessary to restore or update their
-         * configuration here and attempting to put them into D0 again may
-         * confuse some firmware, so avoid doing that.
+         * configuration here and attempting to put them into D0 again is
+         * pointless, so avoid doing that.
          */
-        if (!pci_dev->skip_bus_pm || pm_suspend_via_firmware())
+        if (!(pci_dev->skip_bus_pm && pm_suspend_no_platform()))
                 pci_pm_default_resume_early(pci_dev);
 
         pci_fixup_device(pci_fixup_resume_early, pci_dev);
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 8594001e8be8..f0d262ad7b78 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -209,8 +209,9 @@ extern int suspend_valid_only_mem(suspend_state_t state);
 
 extern unsigned int pm_suspend_global_flags;
 
-#define PM_SUSPEND_FLAG_FW_SUSPEND      (1 << 0)
-#define PM_SUSPEND_FLAG_FW_RESUME       (1 << 1)
+#define PM_SUSPEND_FLAG_FW_SUSPEND      BIT(0)
+#define PM_SUSPEND_FLAG_FW_RESUME       BIT(1)
+#define PM_SUSPEND_FLAG_NO_PLATFORM     BIT(2)
 
 static inline void pm_suspend_clear_flags(void)
 {
@@ -227,6 +228,11 @@ static inline void pm_set_resume_via_firmware(void)
         pm_suspend_global_flags |= PM_SUSPEND_FLAG_FW_RESUME;
 }
 
+static inline void pm_set_suspend_no_platform(void)
+{
+        pm_suspend_global_flags |= PM_SUSPEND_FLAG_NO_PLATFORM;
+}
+
 /**
  * pm_suspend_via_firmware - Check if platform firmware will suspend the system.
  *
@@ -268,6 +274,22 @@ static inline bool pm_resume_via_firmware(void)
         return !!(pm_suspend_global_flags & PM_SUSPEND_FLAG_FW_RESUME);
 }
 
+/**
+ * pm_suspend_no_platform - Check if platform may change device power states.
+ *
+ * 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 power states of devices remain under full control of the
+ * kernel throughout the system-wide suspend and resume cycle in progress (that
+ * is, if a device is put into a certain power state during suspend, it can be
+ * expected to remain in that state during resume).
+ */
+static inline bool pm_suspend_no_platform(void)
+{
+        return !!(pm_suspend_global_flags & PM_SUSPEND_FLAG_NO_PLATFORM);
+}
+
 /* Suspend-to-idle state machnine. */
 enum s2idle_states {
         S2IDLE_STATE_NONE,      /* Not suspended/suspending. */
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 9505101ed2bc..096211299c07 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -493,6 +493,9 @@ int suspend_devices_and_enter(suspend_state_t state)
 
         pm_suspend_target_state = state;
 
+        if (state == PM_SUSPEND_TO_IDLE)
+                pm_set_suspend_no_platform();
+
         error = platform_suspend_begin(state);
         if (error)
                 goto Close;