Merge branch 'pci/pm'

- Set power state to 'unknown' for all devices, not just those with
  drivers, during suspend (Lukas Wunner)

- Skip restoring Resizable BARs and VF Resizable BARs if device doesn't
  respond to config reads, to avoid invalid array accesses (Marco
  Nenciarini)

- Add pci_suspend_retains_context() so drivers can tell whether devices may
  be reset while resuming from suspend due to platform issues; use this in
  nvme to avoid issues on Qcom RCs (Manivannan Sadhasivam)

* pci/pm:
  nvme-pci: Use pci_suspend_retains_context() during suspend
  PCI: qcom: Indicate broken L1SS exit during resume from system suspend
  PCI: Indicate context lost if L1SS exit is broken during resume from system suspend
  PCI: Add pci_suspend_retains_context() to check if device state is preserved during suspend
  PCI/IOV: Skip VF Resizable BAR restore on read error
  PCI: Skip Resizable BAR restore on read error
  PCI: Stop setting cached power state to 'unknown' on unbind

drivers/nvme/host/pci.c

@@ -3915,6 +3915,7 @@ static int nvme_suspend(struct device *dev)
 	 * use host managed nvme power settings for lowest idle power if
 	 * possible. This should have quicker resume latency than a full device
 	 * shutdown.  But if the firmware is involved after the suspend or the
+	 * platform has any limitation in waking from low power states or the
 	 * device does not support any non-default power states, shut down the
 	 * device fully.
 	 *
@@ -3923,7 +3924,7 @@ static int nvme_suspend(struct device *dev)
 	 * down, so as to allow the platform to achieve its minimum low-power
 	 * state (which may not be possible if the link is up).
 	 */
-	if (pm_suspend_via_firmware() || !ctrl->npss ||
+	if (!pci_suspend_retains_context(pdev) || !ctrl->npss ||
 	    !pcie_aspm_enabled(pdev) ||
 	    (ndev->ctrl.quirks & NVME_QUIRK_SIMPLE_SUSPEND))
 		return nvme_disable_prepare_reset(ndev, true);

drivers/pci/controller/dwc/pcie-qcom.c

@@ -1368,6 +1368,19 @@ static void qcom_pcie_host_post_init(struct dw_pcie_rp *pp)
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct qcom_pcie *pcie = to_qcom_pcie(pci);
 
+	/*
+	 * During system suspend, the Qcom RC driver may turn off the
+	 * analog circuitry of PHY and remove controller votes to save
+	 * power. If the link is in L1SS and the endpoint asserts CLKREQ#
+	 * to exit L1SS, the time required to wake the system and restore
+	 * the PHY/REFCLK may exceed the L1SS exit timing (L10_REFCLK_ON +
+	 * T_COMMONMODE), resulting in Link Down (LDn) and a reset of the
+	 * endpoint. Set this flag to indicate this limitation to client
+	 * drivers so that they can avoid relying on device state being
+	 * preserved during system suspend.
+	 */
+	pp->bridge->broken_l1ss_resume = true;
+
 	if (pcie->cfg->ops->host_post_init)
 		pcie->cfg->ops->host_post_init(pcie);
 }

drivers/pci/iov.c

@@ -938,12 +938,18 @@ static void sriov_restore_vf_rebar_state(struct pci_dev *dev)
 		return;
 
 	pci_read_config_dword(dev, pos + PCI_VF_REBAR_CTRL, &ctrl);
+	if (PCI_POSSIBLE_ERROR(ctrl))
+		return;
+
 	nbars = FIELD_GET(PCI_VF_REBAR_CTRL_NBAR_MASK, ctrl);
 
 	for (i = 0; i < nbars; i++, pos += 8) {
 		int bar_idx, size;
 
 		pci_read_config_dword(dev, pos + PCI_VF_REBAR_CTRL, &ctrl);
+		if (PCI_POSSIBLE_ERROR(ctrl))
+			return;
+
 		bar_idx = FIELD_GET(PCI_VF_REBAR_CTRL_BAR_IDX, ctrl);
 		size = pci_rebar_bytes_to_size(dev->sriov->barsz[bar_idx]);
 		ctrl &= ~PCI_VF_REBAR_CTRL_BAR_SIZE;

drivers/pci/pci-driver.c

@@ -512,13 +512,6 @@ static void pci_device_remove(struct device *dev)
 	/* Undo the runtime PM settings in local_pci_probe() */
 	pm_runtime_put_sync(dev);
 
-	/*
-	 * If the device is still on, set the power state as "unknown",
-	 * since it might change by the next time we load the driver.
-	 */
-	if (pci_dev->current_state == PCI_D0)
-		pci_dev->current_state = PCI_UNKNOWN;
-
 	/*
 	 * We would love to complain here if pci_dev->is_enabled is set, that
 	 * the driver should have called pci_disable_device(), but the
@@ -893,7 +886,7 @@ static int pci_pm_suspend_noirq(struct device *dev)
 
 	if (!pm) {
 		pci_save_state(pci_dev);
-		goto Fixup;
+		goto set_unknown;
 	}
 
 	if (pm->suspend_noirq) {
@@ -945,6 +938,7 @@ static int pci_pm_suspend_noirq(struct device *dev)
 		goto Fixup;
 	}
 
+set_unknown:
 	pci_pm_set_unknown_state(pci_dev);
 
 	/*

drivers/pci/pci.c

@@ -33,6 +33,7 @@
 #include <asm/dma.h>
 #include <linux/aer.h>
 #include <linux/bitfield.h>
+#include <linux/suspend.h>
 #include "pci.h"
 
 DEFINE_MUTEX(pci_slot_mutex);
@@ -2886,6 +2887,40 @@ void pci_config_pm_runtime_put(struct pci_dev *pdev)
 		pm_runtime_put_sync(parent);
 }
 
+/**
+ * pci_suspend_retains_context - Check if the platform can retain the device
+ *				 context during system suspend
+ * @pdev: PCI device to check
+ *
+ * Return: true if the platform can guarantee to retain the device context,
+ * false otherwise.
+ */
+bool pci_suspend_retains_context(struct pci_dev *pdev)
+{
+	struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus);
+
+	/*
+	 * If the platform firmware (like ACPI) is involved at the end of
+	 * system suspend, device context may not be retained.
+	 */
+	if (pm_suspend_via_firmware())
+		return false;
+
+	/*
+	 * Some host bridges power off the PHY to enter deep low-power
+	 * modes during system suspend. Exiting L1SS from this condition
+	 * may violate timing requirements and result in Link Down (LDn),
+	 * which causes a reset of the device.  On such platforms, the
+	 * endpoint must be prepared for context loss.
+	 */
+	if (bridge && bridge->broken_l1ss_resume)
+		return false;
+
+	/* Assume that the context is retained by default */
+	return true;
+}
+EXPORT_SYMBOL_GPL(pci_suspend_retains_context);
+
 static const struct dmi_system_id bridge_d3_blacklist[] = {
 #ifdef CONFIG_X86
 	{

drivers/pci/rebar.c

@@ -231,6 +231,9 @@ void pci_restore_rebar_state(struct pci_dev *pdev)
 		return;
 
 	pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+	if (PCI_POSSIBLE_ERROR(ctrl))
+		return;
+
 	nbars = FIELD_GET(PCI_REBAR_CTRL_NBAR_MASK, ctrl);
 
 	for (i = 0; i < nbars; i++, pos += 8) {
@@ -238,6 +241,9 @@ void pci_restore_rebar_state(struct pci_dev *pdev)
 		int bar_idx, size;
 
 		pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+		if (PCI_POSSIBLE_ERROR(ctrl))
+			return;
+
 		bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX;
 		res = pci_resource_n(pdev, bar_idx);
 		size = pci_rebar_bytes_to_size(resource_size(res));

include/linux/pci.h

@@ -660,6 +660,8 @@ struct pci_host_bridge {
 	unsigned int	preserve_config:1;	/* Preserve FW resource setup */
 	unsigned int	size_windows:1;		/* Enable root bus sizing */
 	unsigned int	msi_domain:1;		/* Bridge wants MSI domain */
+	unsigned int	broken_l1ss_resume:1;	/* Resuming from L1SS during
+						   system suspend is broken */
 
 	/* Resource alignment requirements */
 	resource_size_t (*align_resource)(struct pci_dev *dev,
@@ -2086,6 +2088,8 @@ pci_release_mem_regions(struct pci_dev *pdev)
 			    pci_select_bars(pdev, IORESOURCE_MEM));
 }
 
+bool pci_suspend_retains_context(struct pci_dev *pdev);
+
 #else /* CONFIG_PCI is not enabled */
 
 static inline void pci_set_flags(int flags) { }
@@ -2244,6 +2248,11 @@ pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
 static inline void pci_free_irq_vectors(struct pci_dev *dev)
 {
 }
+
+static inline bool pci_suspend_retains_context(struct pci_dev *pdev)
+{
+	return true;
+}
 #endif /* CONFIG_PCI */
 
 /* Include architecture-dependent settings and functions */