[PATCH v4 0/4] PCI: Add support for suspending (including runtime) of PCIe ports

[PATCH v4 0/4] 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

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 [4/4].

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

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 (4):
  PCI: No need to set d3cold_allowed to PCIe ports
  PCI: Move PCIe ports to D3 during suspend
  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  |   8 +-
 drivers/pci/pci-driver.c            |  10 +-
 drivers/pci/pci-sysfs.c             |   5 +
 drivers/pci/pci.c                   | 176 ++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.h                   |   2 +
 drivers/pci/pcie/portdrv_core.c     |   2 +
 drivers/pci/pcie/portdrv_pci.c      |  52 ++++++++++-
 drivers/pci/remove.c                |   2 +
 drivers/usb/host/xhci-pci.c         |   2 +-
 include/linux/pci.h                 |   3 +
 12 files changed, 257 insertions(+), 10 deletions(-)

-- 
2.8.0.rc3

[PATCH v4 1/4] PCI: No need to set d3cold_allowed to PCIe ports

[Mika Westerberg]

The Linux PCI core skips PCI bridges and PCIe ports when 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.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.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;
 }
 
-- 
2.8.0.rc3

Re: [PATCH v4 1/4] PCI: No need to set d3cold_allowed to PCIe ports

[Rafael J. Wysocki]

On Mon, Apr 25, 2016 at 11:53 AM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
> The Linux PCI core skips PCI bridges and PCIe ports when 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.
>
> 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;
>  }
>
> --
> 2.8.0.rc3
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH v4 2/4] PCI: Move PCIe ports to 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 which is not good thing in portable devices such as laptops. This may
also 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 moved 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 (we provide
helper functions that should be used to change state of the device, like
pci_d3cold_disable()). 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.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 Documentation/kernel-parameters.txt |   4 +
 drivers/pci/bus.c                   |   1 +
 drivers/pci/pci-driver.c            |  10 +-
 drivers/pci/pci-sysfs.c             |   5 +
 drivers/pci/pci.c                   | 176 ++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.h                   |   2 +
 drivers/pci/remove.c                |   2 +
 drivers/usb/host/xhci-pci.c         |   2 +-
 include/linux/pci.h                 |   3 +
 9 files changed, 200 insertions(+), 5 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 0b3de80ec8f6..90e1f43760be 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3008,6 +3008,10 @@ 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 6c9f5467bc5f..b1738162d69a 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..e3ece0e25fa3 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -777,7 +777,12 @@ 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))
+		/*
+		 * Check if given device can go to low power state. Currently
+		 * we allow normal PCI devices and PCI bridges if their
+		 * bridge_d3 is set.
+		 */
+		if (!pci_has_subordinate(pci_dev) || pci_dev->bridge_d3)
 			pci_prepare_to_sleep(pci_dev);
 	}
 
@@ -1144,7 +1149,6 @@ 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 +1165,6 @@ 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 342b6918bbde..1a0854be5b18 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 25e0327d4429..69878d5e2c2f 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 +2172,165 @@ void pci_config_pm_runtime_put(struct pci_dev *pdev)
 }
 
 /**
+ * pci_bridge_d3_possible - Is it possible to move the bridge to 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;
+
+		/*
+		 * PCIe ports from 2015 and newer should be capable of
+		 * entering 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;
+
+	/*
+	 * The device needs to be allowed to go D3cold and if it is wake
+	 * capable to do so from D3cold. If the device is bridge then it
+	 * needs to have D3 allowed.
+	 */
+	if (dev->no_d3cold || !dev->d3cold_allowed)
+		*d3cold_ok = false;
+	if (device_may_wakeup(&dev->dev) && !pci_pme_capable(dev, PCI_D3cold))
+		*d3cold_ok = false;
+	if (pci_has_subordinate(dev) && !dev->bridge_d3)
+		*d3cold_ok = false;
+
+	return !*d3cold_ok;
+}
+
+/*
+ * pci_bridge_d3_update - Update bridge D3 capabilities
+ * @dev: PCI device which is changed
+ * @remove: Is the device being removed
+ *
+ * Updates 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 +2364,7 @@ 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..1d247e39da0a 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)
 {
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 932ec74909c6..aa7d586710c0 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -296,6 +296,7 @@ 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 */
@@ -1085,6 +1086,8 @@ 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)
-- 
2.8.0.rc3

Re: [PATCH v4 2/4] PCI: Move PCIe ports to D3 during suspend

[Rafael J. Wysocki]

On Mon, Apr 25, 2016 at 11:53 AM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
> 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 which is not good thing in portable devices such as laptops. This may
> also 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 moved 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 (we provide
> helper functions that should be used to change state of the device, like
> pci_d3cold_disable()). 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.
>
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> ---
>  Documentation/kernel-parameters.txt |   4 +
>  drivers/pci/bus.c                   |   1 +
>  drivers/pci/pci-driver.c            |  10 +-
>  drivers/pci/pci-sysfs.c             |   5 +
>  drivers/pci/pci.c                   | 176 ++++++++++++++++++++++++++++++++++++
>  drivers/pci/pci.h                   |   2 +
>  drivers/pci/remove.c                |   2 +
>  drivers/usb/host/xhci-pci.c         |   2 +-
>  include/linux/pci.h                 |   3 +
>  9 files changed, 200 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 0b3de80ec8f6..90e1f43760be 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3008,6 +3008,10 @@ 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 6c9f5467bc5f..b1738162d69a 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..e3ece0e25fa3 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -777,7 +777,12 @@ 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))
> +               /*
> +                * Check if given device can go to low power state. Currently
> +                * we allow normal PCI devices and PCI bridges if their
> +                * bridge_d3 is set.
> +                */
> +               if (!pci_has_subordinate(pci_dev) || pci_dev->bridge_d3)

I'd add a helper for this, say pci_power_manageable() or similar.

>                         pci_prepare_to_sleep(pci_dev);
>         }
>
> @@ -1144,7 +1149,6 @@ 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 +1165,6 @@ 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 342b6918bbde..1a0854be5b18 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 25e0327d4429..69878d5e2c2f 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 +2172,165 @@ void pci_config_pm_runtime_put(struct pci_dev *pdev)
>  }
>
>  /**
> + * pci_bridge_d3_possible - Is it possible to move the bridge to D3

It is better to say "transition" than "move" here IMO.  Or even "put
... into ..".

> + * @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;
> +
> +               /*
> +                * PCIe ports from 2015 and newer should be capable of
> +                * entering D3.

This is more about safety than capability.

I'm sure that older PCIe ports can go to D3 too, but at least some of
them will not work correctly after going back to D0.

So I'd say "It should be safe to put PCIe ports from 2015 or newer into 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;
> +
> +       /*
> +        * The device needs to be allowed to go D3cold and if it is wake
> +        * capable to do so from D3cold. If the device is bridge then it
> +        * needs to have D3 allowed.
> +        */
> +       if (dev->no_d3cold || !dev->d3cold_allowed)
> +               *d3cold_ok = false;
> +       if (device_may_wakeup(&dev->dev) && !pci_pme_capable(dev, PCI_D3cold))
> +               *d3cold_ok = false;
> +       if (pci_has_subordinate(dev) && !dev->bridge_d3)
> +               *d3cold_ok = false;

What about:

bool no_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;

The rest of the patch looks fine.

Re: [PATCH v4 2/4] PCI: Move PCIe ports to D3 during suspend

[Mika Westerberg]

On Tue, Apr 26, 2016 at 11:04:55PM +0200, Rafael J. Wysocki wrote:
> On Mon, Apr 25, 2016 at 11:53 AM, Mika Westerberg
> <mika.westerberg@linux.intel.com> wrote:
> > 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 which is not good thing in portable devices such as laptops. This may
> > also 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 moved 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 (we provide
> > helper functions that should be used to change state of the device, like
> > pci_d3cold_disable()). 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.
> >
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > ---
> >  Documentation/kernel-parameters.txt |   4 +
> >  drivers/pci/bus.c                   |   1 +
> >  drivers/pci/pci-driver.c            |  10 +-
> >  drivers/pci/pci-sysfs.c             |   5 +
> >  drivers/pci/pci.c                   | 176 ++++++++++++++++++++++++++++++++++++
> >  drivers/pci/pci.h                   |   2 +
> >  drivers/pci/remove.c                |   2 +
> >  drivers/usb/host/xhci-pci.c         |   2 +-
> >  include/linux/pci.h                 |   3 +
> >  9 files changed, 200 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> > index 0b3de80ec8f6..90e1f43760be 100644
> > --- a/Documentation/kernel-parameters.txt
> > +++ b/Documentation/kernel-parameters.txt
> > @@ -3008,6 +3008,10 @@ 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 6c9f5467bc5f..b1738162d69a 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..e3ece0e25fa3 100644
> > --- a/drivers/pci/pci-driver.c
> > +++ b/drivers/pci/pci-driver.c
> > @@ -777,7 +777,12 @@ 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))
> > +               /*
> > +                * Check if given device can go to low power state. Currently
> > +                * we allow normal PCI devices and PCI bridges if their
> > +                * bridge_d3 is set.
> > +                */
> > +               if (!pci_has_subordinate(pci_dev) || pci_dev->bridge_d3)
> 
> I'd add a helper for this, say pci_power_manageable() or similar.

OK

> >                         pci_prepare_to_sleep(pci_dev);
> >         }
> >
> > @@ -1144,7 +1149,6 @@ 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 +1165,6 @@ 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 342b6918bbde..1a0854be5b18 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 25e0327d4429..69878d5e2c2f 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 +2172,165 @@ void pci_config_pm_runtime_put(struct pci_dev *pdev)
> >  }
> >
> >  /**
> > + * pci_bridge_d3_possible - Is it possible to move the bridge to D3
> 
> It is better to say "transition" than "move" here IMO.  Or even "put
> ... into ..".

I'll use "put the bridge into D3". Thanks.

> > + * @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;
> > +
> > +               /*
> > +                * PCIe ports from 2015 and newer should be capable of
> > +                * entering D3.
> 
> This is more about safety than capability.
> 
> I'm sure that older PCIe ports can go to D3 too, but at least some of
> them will not work correctly after going back to D0.
> 
> So I'd say "It should be safe to put PCIe ports from 2015 or newer into D3".

OK

> > +                */
> > +               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;
> > +
> > +       /*
> > +        * The device needs to be allowed to go D3cold and if it is wake
> > +        * capable to do so from D3cold. If the device is bridge then it
> > +        * needs to have D3 allowed.
> > +        */
> > +       if (dev->no_d3cold || !dev->d3cold_allowed)
> > +               *d3cold_ok = false;
> > +       if (device_may_wakeup(&dev->dev) && !pci_pme_capable(dev, PCI_D3cold))
> > +               *d3cold_ok = false;
> > +       if (pci_has_subordinate(dev) && !dev->bridge_d3)
> > +               *d3cold_ok = false;
> 
> What about:
> 
> bool no_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;

Works for me.

Thanks for the comments!

Re: [PATCH v4 2/4] PCI: Move PCIe ports to D3 during suspend

[Lukas Wunner]

Hi Rafael,

On Tue, Apr 26, 2016 at 11:04:55PM +0200, Rafael J. Wysocki wrote:
> On Mon, Apr 25, 2016 at 11:53 AM, Mika Westerberg
> <mika.westerberg@linux.intel.com> wrote:
[snip]
> > --- a/drivers/pci/pci-driver.c
> > +++ b/drivers/pci/pci-driver.c
> > @@ -777,7 +777,12 @@ 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))
> > +               /*
> > +                * Check if given device can go to low power state. Currently
> > +                * we allow normal PCI devices and PCI bridges if their
> > +                * bridge_d3 is set.
> > +                */
> > +               if (!pci_has_subordinate(pci_dev) || pci_dev->bridge_d3)
> 
> I'd add a helper for this, say pci_power_manageable() or similar.

He had a helper for this in a prior version and removed it on my
suggestion. Sorry Mika, guess I caused you additional work there. :-/

Best regards,

Lukas

Re: [PATCH v4 2/4] PCI: Move PCIe ports to D3 during suspend

[Mika Westerberg]

On Thu, Apr 28, 2016 at 04:25:19PM +0200, Lukas Wunner wrote:
> He had a helper for this in a prior version and removed it on my
> suggestion. Sorry Mika, guess I caused you additional work there. :-/

No worries :-)

[PATCH v4 3/4] 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 | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index fa49f9143b80..d64ce8aa99b3 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -756,8 +756,10 @@ static void hotplug_event(u32 type, struct acpiphp_context *context)
 
 	acpi_lock_hp_context();
 	bridge = context->bridge;
-	if (bridge)
+	if (bridge) {
 		get_bridge(bridge);
+		pm_runtime_get_sync(&bridge->pci_dev->dev);
+	}
 
 	acpi_unlock_hp_context();
 
@@ -797,8 +799,10 @@ static void hotplug_event(u32 type, struct acpiphp_context *context)
 	}
 
 	pci_unlock_rescan_remove();
-	if (bridge)
+	if (bridge) {
+		pm_runtime_put(&bridge->pci_dev->dev);
 		put_bridge(bridge);
+	}
 }
 
 static int acpiphp_hotplug_notify(struct acpi_device *adev, u32 type)
-- 
2.8.0.rc3

Re: [PATCH v4 3/4] ACPI / hotplug / PCI: Runtime resume bridge before rescan

[Rafael J. Wysocki]

On Mon, Apr 25, 2016 at 11:53 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 | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> index fa49f9143b80..d64ce8aa99b3 100644
> --- a/drivers/pci/hotplug/acpiphp_glue.c
> +++ b/drivers/pci/hotplug/acpiphp_glue.c
> @@ -756,8 +756,10 @@ static void hotplug_event(u32 type, struct acpiphp_context *context)
>
>         acpi_lock_hp_context();
>         bridge = context->bridge;
> -       if (bridge)
> +       if (bridge) {
>                 get_bridge(bridge);
> +               pm_runtime_get_sync(&bridge->pci_dev->dev);
> +       }
>
>         acpi_unlock_hp_context();
>
> @@ -797,8 +799,10 @@ static void hotplug_event(u32 type, struct acpiphp_context *context)
>         }
>
>         pci_unlock_rescan_remove();
> -       if (bridge)
> +       if (bridge) {
> +               pm_runtime_put(&bridge->pci_dev->dev);
>                 put_bridge(bridge);
> +       }
>  }
>
>  static int acpiphp_hotplug_notify(struct acpi_device *adev, u32 type)
> --
> 2.8.0.rc3
>
> --
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[PATCH v4 4/4] 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 10ms 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

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/pci/pcie/portdrv_core.c |  2 ++
 drivers/pci/pcie/portdrv_pci.c  | 51 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 88122dc2e1b1..65b1a624826b 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>
@@ -343,6 +344,7 @@ static int pcie_device_init(struct pci_dev *pdev, int service, int irq)
 		     get_descriptor_id(pci_pcie_type(pdev), service));
 	device->parent = &pdev->dev;
 	device_enable_async_suspend(device);
+	pm_runtime_no_callbacks(device);
 
 	retval = device_register(device);
 	if (retval) {
diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index 6c6bb03392ea..22ee69dc8773 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -93,6 +93,27 @@ 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)
+{
+	pm_runtime_mark_last_busy(dev);
+	return 0;
+}
+
+static int pcie_port_runtime_idle(struct device *dev)
+{
+	/*
+	 * Rely 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 +122,9 @@ 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 +158,38 @@ 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 10ms 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, 10);
+		pm_runtime_use_autosuspend(&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);
 }
 
-- 
2.8.0.rc3

Re: [PATCH v4 4/4] PCI: Add runtime PM support for PCIe ports

[Rafael J. Wysocki]

On Mon, Apr 25, 2016 at 11:53 AM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
> 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 10ms 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
>
> 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 |  2 ++
>  drivers/pci/pcie/portdrv_pci.c  | 51 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 53 insertions(+)
>
> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 88122dc2e1b1..65b1a624826b 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>
> @@ -343,6 +344,7 @@ static int pcie_device_init(struct pci_dev *pdev, int service, int irq)
>                      get_descriptor_id(pci_pcie_type(pdev), service));
>         device->parent = &pdev->dev;
>         device_enable_async_suspend(device);
> +       pm_runtime_no_callbacks(device);
>
>         retval = device_register(device);
>         if (retval) {
> diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
> index 6c6bb03392ea..22ee69dc8773 100644
> --- a/drivers/pci/pcie/portdrv_pci.c
> +++ b/drivers/pci/pcie/portdrv_pci.c
> @@ -93,6 +93,27 @@ 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)
> +{
> +       pm_runtime_mark_last_busy(dev);
> +       return 0;
> +}
> +
> +static int pcie_port_runtime_idle(struct device *dev)
> +{
> +       /*
> +        * Rely 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 +122,9 @@ 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 +158,38 @@ 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 10ms 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, 10);
> +               pm_runtime_use_autosuspend(&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);
>  }
>
> --
> 2.8.0.rc3
>
> --
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Re: [PATCH v4 4/4] PCI: Add runtime PM support for PCIe ports

[Lukas Wunner]

Hi Mika,

I've rebased my Thunderbolt runtime pm patches on v4 of your patches
and everything seems to still work fine. d3cold_allowed also works
as it should now.

As said I've amended my series to allow runtime pm on hotplug ports
if they're Thunderbolt ports on a Mac:
https://github.com/l1k/linux/commit/a6810db929485c7fc8677f265b1c68e31879ce61

I've also reviewed the patches one more time and spotted only this
small nit:

On Mon, Apr 25, 2016 at 12:53:24PM +0300, Mika Westerberg wrote:
> +static int pcie_port_runtime_resume(struct device *dev)
> +{
> +	pm_runtime_mark_last_busy(dev);
> +	return 0;
> +}

The PM core seems to do this automatically, see rpm_resume():
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/base/power/runtime.c#n749

So you could just drop the .runtime_resume entry here and it shouldn't
result in any functional change:

> @@ -101,6 +122,9 @@ 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,

Best regards,

Lukas

Re: [PATCH v4 4/4] PCI: Add runtime PM support for PCIe ports

[Mika Westerberg]

On Thu, Apr 28, 2016 at 04:22:16PM +0200, Lukas Wunner wrote:
> Hi Mika,
> 
> I've rebased my Thunderbolt runtime pm patches on v4 of your patches
> and everything seems to still work fine. d3cold_allowed also works
> as it should now.

Cool, thanks for testing.

> As said I've amended my series to allow runtime pm on hotplug ports
> if they're Thunderbolt ports on a Mac:
> https://github.com/l1k/linux/commit/a6810db929485c7fc8677f265b1c68e31879ce61

If we are going to add more conditions, I think it makes sense to
introduce pcie_port_runtime_pm_possible() or similar which includes all
these checks.

> I've also reviewed the patches one more time and spotted only this
> small nit:
> 
> On Mon, Apr 25, 2016 at 12:53:24PM +0300, Mika Westerberg wrote:
> > +static int pcie_port_runtime_resume(struct device *dev)
> > +{
> > +	pm_runtime_mark_last_busy(dev);
> > +	return 0;
> > +}
> 
> The PM core seems to do this automatically, see rpm_resume():
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/base/power/runtime.c#n749
> 
> So you could just drop the .runtime_resume entry here and it shouldn't
> result in any functional change:
> 
> > @@ -101,6 +122,9 @@ 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,

Hmm, PM core calls pci_pm_runtime_resume() for PCI drivers which then
delegates to driver->runtime_resume() if set. However, if it is missing
it just returns -ENOSYS and does not put the device back to D0.

So if I'm reading this right we actually need to provide
pcie_port_runtime_resume().

Re: [PATCH v4 4/4] PCI: Add runtime PM support for PCIe ports

[Rafael J. Wysocki]

On Thu, Apr 28, 2016 at 5:13 PM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
> On Thu, Apr 28, 2016 at 04:22:16PM +0200, Lukas Wunner wrote:
>> Hi Mika,
>>
>> I've rebased my Thunderbolt runtime pm patches on v4 of your patches
>> and everything seems to still work fine. d3cold_allowed also works
>> as it should now.
>
> Cool, thanks for testing.
>
>> As said I've amended my series to allow runtime pm on hotplug ports
>> if they're Thunderbolt ports on a Mac:
>> https://github.com/l1k/linux/commit/a6810db929485c7fc8677f265b1c68e31879ce61
>
> If we are going to add more conditions, I think it makes sense to
> introduce pcie_port_runtime_pm_possible() or similar which includes all
> these checks.
>
>> I've also reviewed the patches one more time and spotted only this
>> small nit:
>>
>> On Mon, Apr 25, 2016 at 12:53:24PM +0300, Mika Westerberg wrote:
>> > +static int pcie_port_runtime_resume(struct device *dev)
>> > +{
>> > +   pm_runtime_mark_last_busy(dev);
>> > +   return 0;
>> > +}
>>
>> The PM core seems to do this automatically, see rpm_resume():
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/base/power/runtime.c#n749
>>
>> So you could just drop the .runtime_resume entry here and it shouldn't
>> result in any functional change:
>>
>> > @@ -101,6 +122,9 @@ 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,
>
> Hmm, PM core calls pci_pm_runtime_resume() for PCI drivers which then
> delegates to driver->runtime_resume() if set. However, if it is missing
> it just returns -ENOSYS and does not put the device back to D0.
>
> So if I'm reading this right we actually need to provide
> pcie_port_runtime_resume().

You do, but it could just return 0.

The suggestion seems to be that pm_runtime_mark_last_busy() is not
needed as the core will invoke it anyway.

Re: [PATCH v4 4/4] PCI: Add runtime PM support for PCIe ports

[Mika Westerberg]

On Thu, Apr 28, 2016 at 05:31:58PM +0200, Rafael J. Wysocki wrote:
> > Hmm, PM core calls pci_pm_runtime_resume() for PCI drivers which then
> > delegates to driver->runtime_resume() if set. However, if it is missing
> > it just returns -ENOSYS and does not put the device back to D0.
> >
> > So if I'm reading this right we actually need to provide
> > pcie_port_runtime_resume().
> 
> You do, but it could just return 0.
> 
> The suggestion seems to be that pm_runtime_mark_last_busy() is not
> needed as the core will invoke it anyway.

Ah, got it now. Thanks for the clarification!

Re: [PATCH v4 4/4] PCI: Add runtime PM support for PCIe ports

[Lukas Wunner]

Hi Mika,

On Thu, Apr 28, 2016 at 06:13:56PM +0300, Mika Westerberg wrote:
> On Thu, Apr 28, 2016 at 04:22:16PM +0200, Lukas Wunner wrote:
> > As said I've amended my series to allow runtime pm on hotplug ports
> > if they're Thunderbolt ports on a Mac:
> > https://github.com/l1k/linux/commit/a6810db929485c7fc8677f265b1c68e31879ce61
> 
> If we are going to add more conditions, I think it makes sense to
> introduce pcie_port_runtime_pm_possible() or similar which includes all
> these checks.

Initially I reintroduced that in my patch (bikeshedded the name to
pcie_port_can_runtime_suspend() though ;) ), then decided to throw
it away because I'm just adding a one-liner for Thunderbolt on Macs
to the if-condition. Your call. :)

If you decide to reintroduce it, you could use IS_ENABLED to avoid
having to declare an additional inline stub that returns false, e.g.

if (IS_ENABLED(CONFIG_PM) && pcie_port_can_runtime_suspend()) {
	...
	pm_runtime_allow(&dev->dev);
}


> > So you could just drop the .runtime_resume entry here and it shouldn't
> > result in any functional change:
> > 
> > > @@ -101,6 +122,9 @@ 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,
> 
> Hmm, PM core calls pci_pm_runtime_resume() for PCI drivers which then
> delegates to driver->runtime_resume() if set. However, if it is missing
> it just returns -ENOSYS and does not put the device back to D0.
> 
> So if I'm reading this right we actually need to provide
> pcie_port_runtime_resume().

Ugh, you're right.

Best regards,

Lukas