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Subject[PATCH] PCI: PM: Avoid skipping bus-level PM on platforms without ACPI
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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>
---
drivers/pci/pci-driver.c | 8 ++++----
include/linux/suspend.h | 26 ++++++++++++++++++++++++--
kernel/power/suspend.c | 3 +++
3 files changed, 31 insertions(+), 6 deletions(-)

Index: linux-pm/include/linux/suspend.h
===================================================================
--- linux-pm.orig/include/linux/suspend.h
+++ linux-pm/include/linux/suspend.h
@@ -209,8 +209,9 @@ extern int suspend_valid_only_mem(suspen

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_fir
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_firmwar
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. */
Index: linux-pm/kernel/power/suspend.c
===================================================================
--- linux-pm.orig/kernel/power/suspend.c
+++ linux-pm/kernel/power/suspend.c
@@ -493,6 +493,9 @@ int suspend_devices_and_enter(suspend_st

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;
Index: linux-pm/drivers/pci/pci-driver.c
===================================================================
--- linux-pm.orig/drivers/pci/pci-driver.c
+++ linux-pm/drivers/pci/pci-driver.c
@@ -877,7 +877,7 @@ static int pci_pm_suspend_noirq(struct d
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;
}
@@ -932,10 +932,10 @@ static int pci_pm_resume_noirq(struct de
/*
* 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);


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