PCI/PM: add PCIe runtime D3cold support

This patch adds runtime D3cold support and corresponding ACPI platform
support.  This patch only enables runtime D3cold support; it does not
enable D3cold support during system suspend/hibernate.

D3cold is the deepest power saving state for a PCIe device, where its main
power is removed.  While it is in D3cold, you can't access the device at
all, not even its configuration space (which is still accessible in D3hot).
Therefore the PCI PM registers can not be used to transition into/out of
the D3cold state; that must be done by platform logic such as ACPI _PR3.

To support wakeup from D3cold, a system may provide auxiliary power, which
allows a device to request wakeup using a Beacon or the sideband WAKE#
signal.  WAKE# is usually connected to platform logic such as ACPI GPE.
This is quite different from other power saving states, where devices
request wakeup via a PME message on the PCIe link.

Some devices, such as those in plug-in slots, have no direct platform
logic.  For example, there is usually no ACPI _PR3 for them.  D3cold
support for these devices can be done via the PCIe Downstream Port leading
to the device.  When the PCIe port is powered on/off, the device is powered
on/off too.  Wakeup events from the device will be notified to the
corresponding PCIe port.

For more information about PCIe D3cold and corresponding ACPI support,
please refer to:

- PCI Express Base Specification Revision 2.0
- Advanced Configuration and Power Interface Specification Revision 5.0

[bhelgaas: changelog]
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>
Originally-by: Zheng Yan <zheng.z.yan@intel.com>
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 19 insertions, 4 deletions

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index a9efebc..e1658af 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -48,6 +48,12 @@ static void pci_acpi_wake_dev(acpi_handle handle, u32 event, void *context)
 	if (event != ACPI_NOTIFY_DEVICE_WAKE || !pci_dev)
 		return;
 
+	if (pci_dev->current_state == PCI_D3cold) {
+		pci_wakeup_event(pci_dev);
+		pm_runtime_resume(&pci_dev->dev);
+		return;
+	}
+
 	if (!pci_dev->pm_cap || !pci_dev->pme_support
 	     || pci_check_pme_status(pci_dev)) {
 		if (pci_dev->pme_poll)
@@ -187,10 +193,13 @@ acpi_status pci_acpi_remove_pm_notifier(struct acpi_device *dev)
 
 static pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
 {
-	int acpi_state;
+	int acpi_state, d_max;
 
-	acpi_state = acpi_pm_device_sleep_state(&pdev->dev, NULL,
-						ACPI_STATE_D3);
+	if (pdev->no_d3cold)
+		d_max = ACPI_STATE_D3_HOT;
+	else
+		d_max = ACPI_STATE_D3_COLD;
+	acpi_state = acpi_pm_device_sleep_state(&pdev->dev, NULL, d_max);
 	if (acpi_state < 0)
 		return PCI_POWER_ERROR;
 
@@ -297,7 +306,13 @@ static void acpi_pci_propagate_run_wake(struct pci_bus *bus, bool enable)
 
 static int acpi_pci_run_wake(struct pci_dev *dev, bool enable)
 {
-	if (dev->pme_interrupt)
+	/*
+	 * Per PCI Express Base Specification Revision 2.0 section
+	 * 5.3.3.2 Link Wakeup, platform support is needed for D3cold
+	 * waking up to power on the main link even if there is PME
+	 * support for D3cold
+	 */
+	if (dev->pme_interrupt && !dev->runtime_d3cold)
 		return 0;
 
 	if (!acpi_pm_device_run_wake(&dev->dev, enable))