[PATCH v6 0/5] PCI: Add support for suspending (including runtime) of PCIe ports

[PATCH v6 0/5] PCI: Add support for suspending (including runtime) of PCIe ports

[Mika Westerberg]

Current Linux PCI core does not do any kind of power management to PCIe
ports. This means that we waste energy and consume laptop battery even if
the port has nothing connected to. These patches aim to change that to the
right direction.

Previous versions of the patches can be found below:

  v1: http://www.spinics.net/lists/linux-pci/msg49313.html
  v2: http://www.spinics.net/lists/linux-pci/msg50167.html
  v3: http://www.spinics.net/lists/linux-pci/msg50345.html
  v4: http://www.spinics.net/lists/linux-pci/msg50665.html
  v5: http://www.spinics.net/lists/linux-pci/msg50803.html

This assumes that recent (starting from 2015) PCIe ports are capable of
transition to D3hot/D3cold. We add a new flag to struct pci_dev 'bridge_d3'
that is set whenever the PCI core thinks the port can be put to D3. The
check in pci_pm_suspend_noirq() is then extended to cover devices where
'bridge_d3' is set.

We then add two new functions pci_bridge_d3_device_changed/removed(). These
are used to set and clear 'bridge_d3' whenever there is a change in device
power management policy (or if the device is removed). For example when
userspace forbids the device to enter D3cold pci_bridge_d3_device_changed()
will clear 'bridge_d3' of the upstream bridge.

For all PCI ports where 'bridge_d3' is set we also enable and unblock
runtime PM automatically. Only exception is when the PCIe port claims to
support hotplug. More information about that is in the changelog of
patch [5/5].

Since this also touches xhci, I'm adding Mathias and Greg to check if the
change looks reasonable.

Bjorn, if you are fine with these patches, it would be nice to get these to
linux-next for better testing coverage.

Changes to v5:

  - Add patch "PCI: Power on bridges before scanning new devices" to make
    sure rescanning using sysfs still works.

  - Change patch "ACPI / hotplug / PCI: Runtime resume bridge before
    rescan" to runtime resume in acpiphp_check_bridge() instead of
    hotplug_event().

  - Change runtime PM autosuspend delay from 10ms to 100ms.

  - Call pm_runtime_mark_last_busy() to make sure we do not runtime suspend
    the port immediatly.

Changes to v4:

  - Use "Put PCIe ports into D3" instead of "move" in subject and comments.

  - Add new helper function pci_power_manageable() and use it to check if
    the port can be suspended instead of open-coding it everytime.

  - Changed pci_dev_check_d3cold() to follow what Rafael suggested.

  - Dropped call to pm_runtime_mark_last_busy() in pcie_port_runtime_resume()
    as PM core does that automatically when the function returns 0.

  - Added ACKs from Rafael.

Changes to v3:

  - Make 'no_d3cold' persist for pci_dev. Once this is set through
    pci_d3cold_enable/disable(), it will persist unless changed again using
    the same functions. Those also handle setting and clearing 'bridge_d3'
    as necessary.

  - Add kernel command line parameter "pcie_port_pm=off|force" that can
    be used to forcibly disable/enable the feature.

  - Use runtime PM autosuspend instead of scheduling runtime suspend
    manually

  - Allow runtime PM always except when we are dealing with a hotplug
    bridge. Actual checking whether the port can be suspended is done in
    ->idle() and ->runtime_suspend() hooks based on 'bridge_d3'.

Changes to v2:

  - Renamed and split pci_enable_d3cold() into two functions
    pci_d3cold_enable()/disable().

  - Renamed pci_bridge_pm_update() into two functions
    pci_bridge_d3_device_changed() and pci_bridge_d3_device_removed() that
    should match better what they are doing.

  - Propagate ->bridge_d3 change to upstream bridges in
    pci_bridge_d3_update().

  - Removed pci_can_suspend() in favor of doing ->bridge_d3 check directly
    in pci_pm_suspend_noirq().

  - Extend runtime PM enabling for ports that are using native PCIe
    hotplug.

  - Call pm_runtime_no_callbacks() for PCIe port service devices (the are
    handled by the parent device).

Changes to v1:

  - Dropped patch [2/6] as there is no need to use that function from other
    files anymore.

  - Dropped patches [5-6/6] in favor of using cut-off date.

  - Updated changelog of [1/4] to mention where in the PCI core PCI bridge
    and PCIe ports are skipped from being power managed.

  - Instead of checking at suspend time if it is possible to transition the
    port to D3, do it whenever power management status of a device (below a
    port) is changed or when it is added or removed to the bus.

  - Added patch [3/4] to runtime resume a bridge when ACPI hotplug event is
    received.

Mika Westerberg (5):
  PCI: Don't clear d3cold_allowed for PCIe ports
  PCI: Put PCIe ports into D3 during suspend
  PCI: Power on bridges before scanning new devices
  ACPI / hotplug / PCI: Runtime resume bridge before rescan
  PCI: Add runtime PM support for PCIe ports

 Documentation/kernel-parameters.txt |   4 +
 drivers/pci/bus.c                   |   1 +
 drivers/pci/hotplug/acpiphp_glue.c  |   4 +
 drivers/pci/pci-driver.c            |   5 +-
 drivers/pci/pci-sysfs.c             |   5 ++
 drivers/pci/pci.c                   | 175 ++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.h                   |  11 +++
 drivers/pci/pcie/portdrv_core.c     |   3 +
 drivers/pci/pcie/portdrv_pci.c      |  52 ++++++++++-
 drivers/pci/probe.c                 |   9 ++
 drivers/pci/remove.c                |   2 +
 drivers/usb/host/xhci-pci.c         |   2 +-
 include/linux/pci.h                 |   3 +
 13 files changed, 268 insertions(+), 8 deletions(-)

-- 
2.8.1

[PATCH v6 1/5] PCI: Don't clear d3cold_allowed for PCIe ports

[Mika Westerberg]

The PCI core skips bridges and ports when the system is suspended.  The PCI
core checks return value of pci_has_subordinate() in pci_pm_suspend_noirq()
to skip all devices where it is non-zero (which means PCI bridges and PCIe
ports).

Since PCIe ports are never suspended in the first place, there is no need
to set d3cold_allowed for them.

Tested-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/pci/pcie/portdrv_pci.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index be35da2e105e..6c6bb03392ea 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -134,11 +134,6 @@ static int pcie_portdrv_probe(struct pci_dev *dev,
 		return status;
 
 	pci_save_state(dev);
-	/*
-	 * D3cold may not work properly on some PCIe port, so disable
-	 * it by default.
-	 */
-	dev->d3cold_allowed = false;
 	return 0;
 }
 
-- 
2.8.1

[PATCH v6 2/5] PCI: Put PCIe ports into D3 during suspend

[Mika Westerberg]

Currently the Linux PCI core does not touch power state of PCI bridges and
PCIe ports when system suspend is entered.  Leaving them in D0 consumes
power unnecessarily and may prevent the CPU from entering deeper C-states.

With recent PCIe hardware we can power down the ports to save power given
that we take into account few restrictions:

  - The PCIe port hardware is recent enough, starting from 2015.

  - Devices connected to PCIe ports are effectively in D3cold once the port
    is transitioned to D3 (the config space is not accessible anymore and
    the link may be powered down).

  - Devices behind the PCIe port need to be allowed to transition to D3cold
    and back.  There is a way both drivers and userspace can forbid this.

  - If the device behind the PCIe port is capable of waking the system it
    needs to be able to do so from D3cold.

This patch adds a new flag to struct pci_device called 'bridge_d3'.  This
flag is set and cleared by the PCI core whenever there is a change in power
management state of any of the devices behind the PCIe port.  When system
later on is suspended we only need to check this flag and if it is true
transition the port to D3 otherwise we leave it in D0.

Also provide override mechanism via command line parameter
"pcie_port_pm=[off|force]" that can be used to disable or enable the
feature regardless of the BIOS manufacturing date.

Tested-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 Documentation/kernel-parameters.txt |   4 +
 drivers/pci/bus.c                   |   1 +
 drivers/pci/pci-driver.c            |   5 +-
 drivers/pci/pci-sysfs.c             |   5 ++
 drivers/pci/pci.c                   | 175 ++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.h                   |  11 +++
 drivers/pci/remove.c                |   2 +
 drivers/usb/host/xhci-pci.c         |   2 +-
 include/linux/pci.h                 |   3 +
 9 files changed, 203 insertions(+), 5 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 82b42c958d1c..86edee4cedd4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3047,6 +3047,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 		compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
 			ports driver.
 
+	pcie_port_pm=	[PCIE] PCIe port power management handling:
+		off	Disable power management of all PCIe ports
+		force	Forcibly enable power management of all PCIe ports
+
 	pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
 		nomsi	Do not use MSI for native PCIe PME signaling (this makes
 			all PCIe root ports use INTx for all services).
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index dd7cdbee8029..28731360b457 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -291,6 +291,7 @@ void pci_bus_add_device(struct pci_dev *dev)
 	pci_fixup_device(pci_fixup_final, dev);
 	pci_create_sysfs_dev_files(dev);
 	pci_proc_attach_device(dev);
+	pci_bridge_d3_device_changed(dev);
 
 	dev->match_driver = true;
 	retval = device_attach(&dev->dev);
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index d7ffd66814bb..e39a67c8ef39 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -777,7 +777,7 @@ static int pci_pm_suspend_noirq(struct device *dev)
 
 	if (!pci_dev->state_saved) {
 		pci_save_state(pci_dev);
-		if (!pci_has_subordinate(pci_dev))
+		if (pci_power_manageable(pci_dev))
 			pci_prepare_to_sleep(pci_dev);
 	}
 
@@ -1144,7 +1144,6 @@ static int pci_pm_runtime_suspend(struct device *dev)
 		return -ENOSYS;
 
 	pci_dev->state_saved = false;
-	pci_dev->no_d3cold = false;
 	error = pm->runtime_suspend(dev);
 	if (error) {
 		/*
@@ -1161,8 +1160,6 @@ static int pci_pm_runtime_suspend(struct device *dev)
 
 		return error;
 	}
-	if (!pci_dev->d3cold_allowed)
-		pci_dev->no_d3cold = true;
 
 	pci_fixup_device(pci_fixup_suspend, pci_dev);
 
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index d319a9ca9b7b..bcd10c795284 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -406,6 +406,11 @@ static ssize_t d3cold_allowed_store(struct device *dev,
 		return -EINVAL;
 
 	pdev->d3cold_allowed = !!val;
+	if (pdev->d3cold_allowed)
+		pci_d3cold_enable(pdev);
+	else
+		pci_d3cold_disable(pdev);
+
 	pm_runtime_resume(dev);
 
 	return count;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index c8b4dbdd1bdd..9ff7183e25a2 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -9,6 +9,7 @@
 
 #include <linux/kernel.h>
 #include <linux/delay.h>
+#include <linux/dmi.h>
 #include <linux/init.h>
 #include <linux/of.h>
 #include <linux/of_pci.h>
@@ -101,6 +102,21 @@ unsigned int pcibios_max_latency = 255;
 /* If set, the PCIe ARI capability will not be used. */
 static bool pcie_ari_disabled;
 
+/* Disable bridge_d3 for all PCIe ports */
+static bool pci_bridge_d3_disable;
+/* Force bridge_d3 for all PCIe ports */
+static bool pci_bridge_d3_force;
+
+static int __init pcie_port_pm_setup(char *str)
+{
+	if (!strcmp(str, "off"))
+		pci_bridge_d3_disable = true;
+	else if (!strcmp(str, "force"))
+		pci_bridge_d3_force = true;
+	return 1;
+}
+__setup("pcie_port_pm=", pcie_port_pm_setup);
+
 /**
  * pci_bus_max_busnr - returns maximum PCI bus number of given bus' children
  * @bus: pointer to PCI bus structure to search
@@ -2156,6 +2172,164 @@ void pci_config_pm_runtime_put(struct pci_dev *pdev)
 }
 
 /**
+ * pci_bridge_d3_possible - Is it possible to put the bridge into D3
+ * @bridge: Bridge to check
+ *
+ * This function checks if it is possible to move the bridge to D3.
+ * Currently we only allow D3 for recent enough PCIe ports.
+ */
+static bool pci_bridge_d3_possible(struct pci_dev *bridge)
+{
+	unsigned int year;
+
+	if (!pci_is_pcie(bridge))
+		return false;
+
+	switch (pci_pcie_type(bridge)) {
+	case PCI_EXP_TYPE_ROOT_PORT:
+	case PCI_EXP_TYPE_UPSTREAM:
+	case PCI_EXP_TYPE_DOWNSTREAM:
+		if (pci_bridge_d3_disable)
+			return false;
+		if (pci_bridge_d3_force)
+			return true;
+
+		/*
+		 * It should be safe to put PCIe ports from 2015 or newer
+		 * to D3.
+		 */
+		if (dmi_get_date(DMI_BIOS_DATE, &year, NULL, NULL) &&
+		    year >= 2015) {
+			return true;
+		}
+		break;
+	}
+
+	return false;
+}
+
+static int pci_dev_check_d3cold(struct pci_dev *dev, void *data)
+{
+	bool *d3cold_ok = data;
+	bool no_d3cold;
+
+	/*
+	 * The device needs to be allowed to go D3cold and if it is wake
+	 * capable to do so from D3cold.
+	 */
+	no_d3cold = dev->no_d3cold || !dev->d3cold_allowed ||
+		(device_may_wakeup(&dev->dev) && !pci_pme_capable(dev, PCI_D3cold)) ||
+		!pci_power_manageable(dev);
+
+	*d3cold_ok = !no_d3cold;
+
+	return no_d3cold;
+}
+
+/*
+ * pci_bridge_d3_update - Update bridge D3 capabilities
+ * @dev: PCI device which is changed
+ * @remove: Is the device being removed
+ *
+ * Update upstream bridge PM capabilities accordingly depending on if the
+ * device PM configuration was changed or the device is being removed.  The
+ * change is also propagated upstream.
+ */
+static void pci_bridge_d3_update(struct pci_dev *dev, bool remove)
+{
+	struct pci_dev *bridge;
+	bool d3cold_ok = true;
+
+	bridge = pci_upstream_bridge(dev);
+	if (!bridge || !pci_bridge_d3_possible(bridge))
+		return;
+
+	pci_dev_get(bridge);
+	/*
+	 * If the device is removed we do not care about its D3cold
+	 * capabilities.
+	 */
+	if (!remove)
+		pci_dev_check_d3cold(dev, &d3cold_ok);
+
+	if (d3cold_ok) {
+		/*
+		 * We need to go through all children to find out if all of
+		 * them can still go to D3cold.
+		 */
+		pci_walk_bus(bridge->subordinate, pci_dev_check_d3cold,
+			     &d3cold_ok);
+	}
+
+	if (bridge->bridge_d3 != d3cold_ok) {
+		bridge->bridge_d3 = d3cold_ok;
+		/* Propagate change to upstream bridges */
+		pci_bridge_d3_update(bridge, false);
+	}
+
+	pci_dev_put(bridge);
+}
+
+/**
+ * pci_bridge_d3_device_changed - Update bridge D3 capabilities on change
+ * @dev: PCI device that was changed
+ *
+ * If a device is added or its PM configuration, such as is it allowed to
+ * enter D3cold, is changed this function updates upstream bridge PM
+ * capabilities accordingly.
+ */
+void pci_bridge_d3_device_changed(struct pci_dev *dev)
+{
+	pci_bridge_d3_update(dev, false);
+}
+
+/**
+ * pci_bridge_d3_device_removed - Update bridge D3 capabilities on remove
+ * @dev: PCI device being removed
+ *
+ * Function updates upstream bridge PM capabilities based on other devices
+ * still left on the bus.
+ */
+void pci_bridge_d3_device_removed(struct pci_dev *dev)
+{
+	pci_bridge_d3_update(dev, true);
+}
+
+/**
+ * pci_d3cold_enable - Enable D3cold for device
+ * @dev: PCI device to handle
+ *
+ * This function can be used in drivers to enable D3cold from the device
+ * they handle.  It also updates upstream PCI bridge PM capabilities
+ * accordingly.
+ */
+void pci_d3cold_enable(struct pci_dev *dev)
+{
+	if (dev->no_d3cold) {
+		dev->no_d3cold = false;
+		pci_bridge_d3_device_changed(dev);
+	}
+}
+EXPORT_SYMBOL_GPL(pci_d3cold_enable);
+
+/**
+ * pci_d3cold_disable - Disable D3cold for device
+ * @dev: PCI device to handle
+ *
+ * This function can be used in drivers to disable D3cold from the device
+ * they handle.  It also updates upstream PCI bridge PM capabilities
+ * accordingly.
+ */
+void pci_d3cold_disable(struct pci_dev *dev)
+{
+	if (!dev->no_d3cold) {
+		dev->no_d3cold = true;
+		pci_bridge_d3_device_changed(dev);
+	}
+}
+EXPORT_SYMBOL_GPL(pci_d3cold_disable);
+
+/**
  * pci_pm_init - Initialize PM functions of given PCI device
  * @dev: PCI device to handle.
  */
@@ -2189,6 +2363,7 @@ void pci_pm_init(struct pci_dev *dev)
 	dev->pm_cap = pm;
 	dev->d3_delay = PCI_PM_D3_WAIT;
 	dev->d3cold_delay = PCI_PM_D3COLD_WAIT;
+	dev->bridge_d3 = pci_bridge_d3_possible(dev);
 	dev->d3cold_allowed = true;
 
 	dev->d1_support = false;
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index a814bbb80fcb..9730c474b016 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -82,6 +82,8 @@ void pci_pm_init(struct pci_dev *dev);
 void pci_ea_init(struct pci_dev *dev);
 void pci_allocate_cap_save_buffers(struct pci_dev *dev);
 void pci_free_cap_save_buffers(struct pci_dev *dev);
+void pci_bridge_d3_device_changed(struct pci_dev *dev);
+void pci_bridge_d3_device_removed(struct pci_dev *dev);
 
 static inline void pci_wakeup_event(struct pci_dev *dev)
 {
@@ -94,6 +96,15 @@ static inline bool pci_has_subordinate(struct pci_dev *pci_dev)
 	return !!(pci_dev->subordinate);
 }
 
+static inline bool pci_power_manageable(struct pci_dev *pci_dev)
+{
+	/*
+	 * Currently we allow normal PCI devices and PCI bridges transition
+	 * into D3 if their bridge_d3 is set.
+	 */
+	return !pci_has_subordinate(pci_dev) || pci_dev->bridge_d3;
+}
+
 struct pci_vpd_ops {
 	ssize_t (*read)(struct pci_dev *dev, loff_t pos, size_t count, void *buf);
 	ssize_t (*write)(struct pci_dev *dev, loff_t pos, size_t count, const void *buf);
diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index 8982026637d5..d1ef7acf6930 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -96,6 +96,8 @@ static void pci_remove_bus_device(struct pci_dev *dev)
 		dev->subordinate = NULL;
 	}
 
+	pci_bridge_d3_device_removed(dev);
+
 	pci_destroy_dev(dev);
 }
 
diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index 48672fac7ff3..ac352fe391f4 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -382,7 +382,7 @@ static int xhci_pci_suspend(struct usb_hcd *hcd, bool do_wakeup)
 	 * need to have the registers polled during D3, so avoid D3cold.
 	 */
 	if (xhci->quirks & XHCI_COMP_MODE_QUIRK)
-		pdev->no_d3cold = true;
+		pci_d3cold_disable(pdev);
 
 	if (xhci->quirks & XHCI_PME_STUCK_QUIRK)
 		xhci_pme_quirk(hcd);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index b67e4df20801..6a27454d2abd 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -294,6 +294,7 @@ struct pci_dev {
 	unsigned int	d2_support:1;	/* Low power state D2 is supported */
 	unsigned int	no_d1d2:1;	/* D1 and D2 are forbidden */
 	unsigned int	no_d3cold:1;	/* D3cold is forbidden */
+	unsigned int	bridge_d3:1;	/* Allow D3 for bridge */
 	unsigned int	d3cold_allowed:1;	/* D3cold is allowed by user */
 	unsigned int	mmio_always_on:1;	/* disallow turning off io/mem
 						   decoding during bar sizing */
@@ -1083,6 +1084,8 @@ int pci_back_from_sleep(struct pci_dev *dev);
 bool pci_dev_run_wake(struct pci_dev *dev);
 bool pci_check_pme_status(struct pci_dev *dev);
 void pci_pme_wakeup_bus(struct pci_bus *bus);
+void pci_d3cold_enable(struct pci_dev *dev);
+void pci_d3cold_disable(struct pci_dev *dev);
 
 static inline int pci_enable_wake(struct pci_dev *dev, pci_power_t state,
 				  bool enable)
-- 
2.8.1

[PATCH v6 3/5] PCI: Power on bridges before scanning new devices

[Mika Westerberg]

When a PCI device is removed through sysfs interface the upstream bridge
(PCIe port) can be runtime suspended if it was the last device on that bus.
Now, if the bridge is in D3 we cannot find devices below the bridge
anymore.  For example following fails to find the removed device again:

  # echo 1 > /sys/bus/pci/devices/0000:00:01.0/0000:01:00.0/remove
  # echo 1 > /sys/bus/pci/devices/0000:00:01.0/rescan

Where 0000:00:01.0 is the bridge device.

In order to be able to rescan devices below the bridge add
pm_runtime_get_sync()/pm_runtime_put() calls to pci_scan_bridge().  This
should keep bridges powered on while their children devices are being
scanned.

Reported-by: Peter Wu <peter@lekensteyn.nl>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/pci/probe.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8e3ef720997d..11a802daf242 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -16,6 +16,7 @@
 #include <linux/aer.h>
 #include <linux/acpi.h>
 #include <linux/irqdomain.h>
+#include <linux/pm_runtime.h>
 #include "pci.h"
 
 #define CARDBUS_LATENCY_TIMER	176	/* secondary latency timer */
@@ -832,6 +833,12 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
 	u8 primary, secondary, subordinate;
 	int broken = 0;
 
+	/*
+	 * Make sure the bridge is powered on to be able to access config
+	 * space of devices below it.
+	 */
+	pm_runtime_get_sync(&dev->dev);
+
 	pci_read_config_dword(dev, PCI_PRIMARY_BUS, &buses);
 	primary = buses & 0xFF;
 	secondary = (buses >> 8) & 0xFF;
@@ -1012,6 +1019,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
 out:
 	pci_write_config_word(dev, PCI_BRIDGE_CONTROL, bctl);
 
+	pm_runtime_put(&dev->dev);
+
 	return max;
 }
 EXPORT_SYMBOL(pci_scan_bridge);
-- 
2.8.1

[PATCH v6 4/5] ACPI / hotplug / PCI: Runtime resume bridge before rescan

[Mika Westerberg]

If a PCI bridge (or PCIe port) that is runtime suspended gets an ACPI
hotplug event, such as BUS_CHECK we need to make sure it is resumed before
devices below the bridge are re-scanned. Otherwise the devices behind the
port are not accessible and will be treated as hot-unplugged.

To fix this, resume PCI bridges from runtime suspend while rescanning.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/pci/hotplug/acpiphp_glue.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index fa49f9143b80..6a33ddcfa20b 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -675,6 +675,8 @@ static void acpiphp_check_bridge(struct acpiphp_bridge *bridge)
 	if (bridge->is_going_away)
 		return;
 
+	pm_runtime_get_sync(&bridge->pci_dev->dev);
+
 	list_for_each_entry(slot, &bridge->slots, node) {
 		struct pci_bus *bus = slot->bus;
 		struct pci_dev *dev, *tmp;
@@ -694,6 +696,8 @@ static void acpiphp_check_bridge(struct acpiphp_bridge *bridge)
 			disable_slot(slot);
 		}
 	}
+
+	pm_runtime_put(&bridge->pci_dev->dev);
 }
 
 /*
-- 
2.8.1

[PATCH v6 5/5] PCI: Add runtime PM support for PCIe ports

[Mika Westerberg]

Add back runtime PM support for PCIe ports that was removed in
commit fe9a743a2601 ("PCI/PM: Drop unused runtime PM support code for PCIe
ports").

First of all we cannot enable it automatically for all ports since there
has been problems previously as can be seen in [1].  In summary suspended
PCIe ports were not able to deal with ACPI-based hotplug reliably.  One
reason why this might happen is the fact that when a PCIe port is powered
down, config space access to the devices behind the port is not possible.
If the BIOS hotplug SMI handler assumes the port is always in D0 it will
not be able to find the hotplugged devices.  To be on the safe side only
enable runtime PM if the port does not claim to support hotplug.

For PCIe ports not using hotplug, we enable and allow runtime PM
automatically.  Since 'bridge_d3' can be changed any time we check this in
driver ->runtime_idle() and ->runtime_suspend() and only allow runtime
suspend if the flag is still set.  Use autosuspend with default of 100ms
idle time to prevent the port from repeatedly suspending and resuming on
continuous configuration space access of devices behind the port.

The actual power transition to D3 and back is handled in the PCI core.

Idea to automatically unblock (allow) runtime PM for PCIe ports came from
Dave Airlie.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=53811

This includes a fix for lockdep issue reported by Valdis Kletnieks.

Tested-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/pci/pcie/portdrv_core.c |  3 +++
 drivers/pci/pcie/portdrv_pci.c  | 51 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 32d4d0a3d20e..e9270b4026f3 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/pm.h>
+#include <linux/pm_runtime.h>
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/pcieport_if.h>
@@ -342,6 +343,8 @@ static int pcie_device_init(struct pci_dev *pdev, int service, int irq)
 		return retval;
 	}
 
+	pm_runtime_no_callbacks(device);
+
 	return 0;
 }
 
diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index 6c6bb03392ea..70d7ad8c6d17 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -93,6 +93,26 @@ static int pcie_port_resume_noirq(struct device *dev)
 	return 0;
 }
 
+static int pcie_port_runtime_suspend(struct device *dev)
+{
+	return to_pci_dev(dev)->bridge_d3 ? 0 : -EBUSY;
+}
+
+static int pcie_port_runtime_resume(struct device *dev)
+{
+	return 0;
+}
+
+static int pcie_port_runtime_idle(struct device *dev)
+{
+	/*
+	 * Assume the PCI core has set bridge_d3 whenever it thinks the port
+	 * should be good to go to D3.  Everything else, including moving
+	 * the port to D3, is handled by the PCI core.
+	 */
+	return to_pci_dev(dev)->bridge_d3 ? 0 : -EBUSY;
+}
+
 static const struct dev_pm_ops pcie_portdrv_pm_ops = {
 	.suspend	= pcie_port_device_suspend,
 	.resume		= pcie_port_device_resume,
@@ -101,6 +121,9 @@ static const struct dev_pm_ops pcie_portdrv_pm_ops = {
 	.poweroff	= pcie_port_device_suspend,
 	.restore	= pcie_port_device_resume,
 	.resume_noirq	= pcie_port_resume_noirq,
+	.runtime_suspend = pcie_port_runtime_suspend,
+	.runtime_resume	= pcie_port_runtime_resume,
+	.runtime_idle	= pcie_port_runtime_idle,
 };
 
 #define PCIE_PORTDRV_PM_OPS	(&pcie_portdrv_pm_ops)
@@ -134,11 +157,39 @@ static int pcie_portdrv_probe(struct pci_dev *dev,
 		return status;
 
 	pci_save_state(dev);
+
+	/*
+	 * Prevent runtime PM if the port is advertising support for PCIe
+	 * hotplug.  Otherwise the BIOS hotplug SMI code might not be able
+	 * to enumerate devices behind this port properly (the port is
+	 * powered down preventing all config space accesses to the
+	 * subordinate devices).  We can't be sure for native PCIe hotplug
+	 * either so prevent that as well.
+	 */
+	if (!dev->is_hotplug_bridge) {
+		/*
+		 * Keep the port resumed 100ms to make sure things like
+		 * config space accesses from userspace (lspci) will not
+		 * cause the port to repeatedly suspend and resume.
+		 */
+		pm_runtime_set_autosuspend_delay(&dev->dev, 100);
+		pm_runtime_use_autosuspend(&dev->dev);
+		pm_runtime_mark_last_busy(&dev->dev);
+		pm_runtime_put_autosuspend(&dev->dev);
+		pm_runtime_allow(&dev->dev);
+	}
+
 	return 0;
 }
 
 static void pcie_portdrv_remove(struct pci_dev *dev)
 {
+	if (!dev->is_hotplug_bridge) {
+		pm_runtime_forbid(&dev->dev);
+		pm_runtime_get_noresume(&dev->dev);
+		pm_runtime_dont_use_autosuspend(&dev->dev);
+	}
+
 	pcie_port_device_remove(dev);
 }
 
-- 
2.8.1

Re: [PATCH v6 3/5] PCI: Power on bridges before scanning new devices

[Rafael J. Wysocki]

On Thu, Jun 2, 2016 at 10:17 AM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
> When a PCI device is removed through sysfs interface the upstream bridge
> (PCIe port) can be runtime suspended if it was the last device on that bus.
> Now, if the bridge is in D3 we cannot find devices below the bridge
> anymore.  For example following fails to find the removed device again:
>
>   # echo 1 > /sys/bus/pci/devices/0000:00:01.0/0000:01:00.0/remove
>   # echo 1 > /sys/bus/pci/devices/0000:00:01.0/rescan
>
> Where 0000:00:01.0 is the bridge device.
>
> In order to be able to rescan devices below the bridge add
> pm_runtime_get_sync()/pm_runtime_put() calls to pci_scan_bridge().  This
> should keep bridges powered on while their children devices are being
> scanned.
>
> Reported-by: Peter Wu <peter@lekensteyn.nl>
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
>  drivers/pci/probe.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 8e3ef720997d..11a802daf242 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -16,6 +16,7 @@
>  #include <linux/aer.h>
>  #include <linux/acpi.h>
>  #include <linux/irqdomain.h>
> +#include <linux/pm_runtime.h>
>  #include "pci.h"
>
>  #define CARDBUS_LATENCY_TIMER  176     /* secondary latency timer */
> @@ -832,6 +833,12 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
>         u8 primary, secondary, subordinate;
>         int broken = 0;
>
> +       /*
> +        * Make sure the bridge is powered on to be able to access config
> +        * space of devices below it.
> +        */
> +       pm_runtime_get_sync(&dev->dev);
> +
>         pci_read_config_dword(dev, PCI_PRIMARY_BUS, &buses);
>         primary = buses & 0xFF;
>         secondary = (buses >> 8) & 0xFF;
> @@ -1012,6 +1019,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
>  out:
>         pci_write_config_word(dev, PCI_BRIDGE_CONTROL, bctl);
>
> +       pm_runtime_put(&dev->dev);
> +
>         return max;
>  }
>  EXPORT_SYMBOL(pci_scan_bridge);
> --

Re: [PATCH v6 4/5] ACPI / hotplug / PCI: Runtime resume bridge before rescan

[Rafael J. Wysocki]

On Thu, Jun 2, 2016 at 10:17 AM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
> If a PCI bridge (or PCIe port) that is runtime suspended gets an ACPI
> hotplug event, such as BUS_CHECK we need to make sure it is resumed before
> devices below the bridge are re-scanned. Otherwise the devices behind the
> port are not accessible and will be treated as hot-unplugged.
>
> To fix this, resume PCI bridges from runtime suspend while rescanning.
>
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
>  drivers/pci/hotplug/acpiphp_glue.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> index fa49f9143b80..6a33ddcfa20b 100644
> --- a/drivers/pci/hotplug/acpiphp_glue.c
> +++ b/drivers/pci/hotplug/acpiphp_glue.c
> @@ -675,6 +675,8 @@ static void acpiphp_check_bridge(struct acpiphp_bridge *bridge)
>         if (bridge->is_going_away)
>                 return;
>
> +       pm_runtime_get_sync(&bridge->pci_dev->dev);
> +
>         list_for_each_entry(slot, &bridge->slots, node) {
>                 struct pci_bus *bus = slot->bus;
>                 struct pci_dev *dev, *tmp;
> @@ -694,6 +696,8 @@ static void acpiphp_check_bridge(struct acpiphp_bridge *bridge)
>                         disable_slot(slot);
>                 }
>         }
> +
> +       pm_runtime_put(&bridge->pci_dev->dev);
>  }
>
>  /*
> --

Re: [PATCH v6 0/5] PCI: Add support for suspending (including runtime) of PCIe ports

[Lukas Wunner]

On Thu, Jun 02, 2016 at 11:17:10AM +0300, Mika Westerberg wrote:
> Bjorn, if you are fine with these patches, it would be nice to get these to
> linux-next for better testing coverage.
> 
> Changes to v5:
> 
>   - Add patch "PCI: Power on bridges before scanning new devices" to make
>     sure rescanning using sysfs still works.
> 
>   - Change patch "ACPI / hotplug / PCI: Runtime resume bridge before
>     rescan" to runtime resume in acpiphp_check_bridge() instead of
>     hotplug_event().
> 
>   - Change runtime PM autosuspend delay from 10ms to 100ms.
> 
>   - Call pm_runtime_mark_last_busy() to make sure we do not runtime suspend
>     the port immediately.

I've applied v6 of this series to my local tree and tested it with
my Thunderbolt runtime pm patches. Everything seems to still work
fine, so my Tested-by is upheld.

I've also compared this version with the previous one in my tree and
reviewed the changes. I only found a punctuation and spacing change
that Bjorn had made and that isn't included in the commit message of
patch [4/5]:

< hotplug event such as BUS_CHECK, we need to make sure it is resumed before
< devices below the bridge are re-scanned.  Otherwise the devices behind the
---
> hotplug event, such as BUS_CHECK we need to make sure it is resumed before
> devices below the bridge are re-scanned. Otherwise the devices behind the

And this line in the commit message of patch [5/5] suddenly has > 72
chars now:

> Add back runtime PM support for PCIe ports that was removed in
> commit fe9a743a2601 ("PCI/PM: Drop unused runtime PM support code for PCIe

Thanks,

Lukas

Re: [PATCH v6 0/5] PCI: Add support for suspending (including runtime) of PCIe ports

[Mika Westerberg]

On Sun, Jun 05, 2016 at 01:27:18AM +0200, Lukas Wunner wrote:
> On Thu, Jun 02, 2016 at 11:17:10AM +0300, Mika Westerberg wrote:
> > Bjorn, if you are fine with these patches, it would be nice to get these to
> > linux-next for better testing coverage.
> > 
> > Changes to v5:
> > 
> >   - Add patch "PCI: Power on bridges before scanning new devices" to make
> >     sure rescanning using sysfs still works.
> > 
> >   - Change patch "ACPI / hotplug / PCI: Runtime resume bridge before
> >     rescan" to runtime resume in acpiphp_check_bridge() instead of
> >     hotplug_event().
> > 
> >   - Change runtime PM autosuspend delay from 10ms to 100ms.
> > 
> >   - Call pm_runtime_mark_last_busy() to make sure we do not runtime suspend
> >     the port immediately.
> 
> I've applied v6 of this series to my local tree and tested it with
> my Thunderbolt runtime pm patches. Everything seems to still work
> fine, so my Tested-by is upheld.

Great, thanks!

> I've also compared this version with the previous one in my tree and
> reviewed the changes. I only found a punctuation and spacing change
> that Bjorn had made and that isn't included in the commit message of
> patch [4/5]:
> 
> < hotplug event such as BUS_CHECK, we need to make sure it is resumed before
> < devices below the bridge are re-scanned.  Otherwise the devices behind the
> ---
> > hotplug event, such as BUS_CHECK we need to make sure it is resumed before
> > devices below the bridge are re-scanned. Otherwise the devices behind the

Hmm, the patch is calling pm_runtime_get_sync()/pm_runtime_put() in
acpiphp_check_bridge() now instead of in hotplug_event() like it was in
the previous version.

> And this line in the commit message of patch [5/5] suddenly has > 72
> chars now:
> 
> > Add back runtime PM support for PCIe ports that was removed in
> > commit fe9a743a2601 ("PCI/PM: Drop unused runtime PM support code for PCIe

Yes, I changed it because checkpatch.pl wants to have commit <COMMIT> in
the same line apparently.

Re: [PATCH v6 0/5] PCI: Add support for suspending (including runtime) of PCIe ports

[Bjorn Helgaas]

On Thu, Jun 02, 2016 at 11:17:10AM +0300, Mika Westerberg wrote:
> Current Linux PCI core does not do any kind of power management to PCIe
> ports. This means that we waste energy and consume laptop battery even if
> the port has nothing connected to. These patches aim to change that to the
> right direction.
> 
> Previous versions of the patches can be found below:
> 
>   v1: http://www.spinics.net/lists/linux-pci/msg49313.html
>   v2: http://www.spinics.net/lists/linux-pci/msg50167.html
>   v3: http://www.spinics.net/lists/linux-pci/msg50345.html
>   v4: http://www.spinics.net/lists/linux-pci/msg50665.html
>   v5: http://www.spinics.net/lists/linux-pci/msg50803.html
> 
> This assumes that recent (starting from 2015) PCIe ports are capable of
> transition to D3hot/D3cold. We add a new flag to struct pci_dev 'bridge_d3'
> that is set whenever the PCI core thinks the port can be put to D3. The
> check in pci_pm_suspend_noirq() is then extended to cover devices where
> 'bridge_d3' is set.
> 
> We then add two new functions pci_bridge_d3_device_changed/removed(). These
> are used to set and clear 'bridge_d3' whenever there is a change in device
> power management policy (or if the device is removed). For example when
> userspace forbids the device to enter D3cold pci_bridge_d3_device_changed()
> will clear 'bridge_d3' of the upstream bridge.
> 
> For all PCI ports where 'bridge_d3' is set we also enable and unblock
> runtime PM automatically. Only exception is when the PCIe port claims to
> support hotplug. More information about that is in the changelog of
> patch [5/5].
> 
> Since this also touches xhci, I'm adding Mathias and Greg to check if the
> change looks reasonable.
> 
> Bjorn, if you are fine with these patches, it would be nice to get these to
> linux-next for better testing coverage.

Applied to pci/pm with Rafael's additional acks, thanks, Mika!