Merge branch 'pci/aspm'

  - disable ASPM L1.2 substate if we don't have LTR (Bjorn Helgaas)

  - respect platform ownership of LTR (Bjorn Helgaas)

* pci/aspm:
  PCI/ACPI: Request LTR control from platform before using it
  PCI/ASPM: Disable ASPM L1.2 Substate if we don't have LTR

drivers/acpi/pci_root.c

@@ -153,6 +153,7 @@ static struct pci_osc_bit_struct pci_osc_control_bit[] = {
 	{ OSC_PCI_EXPRESS_PME_CONTROL, "PME" },
 	{ OSC_PCI_EXPRESS_AER_CONTROL, "AER" },
 	{ OSC_PCI_EXPRESS_CAPABILITY_CONTROL, "PCIeCapability" },
+	{ OSC_PCI_EXPRESS_LTR_CONTROL, "LTR" },
 };
 
 static void decode_osc_bits(struct acpi_pci_root *root, char *msg, u32 word,
@@ -475,6 +476,9 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 		| OSC_PCI_EXPRESS_NATIVE_HP_CONTROL
 		| OSC_PCI_EXPRESS_PME_CONTROL;
 
+	if (IS_ENABLED(CONFIG_PCIEASPM))
+		control |= OSC_PCI_EXPRESS_LTR_CONTROL;
+
 	if (pci_aer_available()) {
 		if (aer_acpi_firmware_first())
 			dev_info(&device->dev,
@@ -905,6 +909,8 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
 		host_bridge->native_aer = 0;
 	if (!(root->osc_control_set & OSC_PCI_EXPRESS_PME_CONTROL))
 		host_bridge->native_pme = 0;
+	if (!(root->osc_control_set & OSC_PCI_EXPRESS_LTR_CONTROL))
+		host_bridge->native_ltr = 0;
 
 	pci_scan_child_bus(bus);
 	pci_set_host_bridge_release(host_bridge, acpi_pci_root_release_info,

drivers/pci/pcie/aspm.c

@@ -400,6 +400,15 @@ static void pcie_get_aspm_reg(struct pci_dev *pdev,
 		info->l1ss_cap = 0;
 		return;
 	}
+
+	/*
+	 * If we don't have LTR for the entire path from the Root Complex
+	 * to this device, we can't use ASPM L1.2 because it relies on the
+	 * LTR_L1.2_THRESHOLD.  See PCIe r4.0, secs 5.5.4, 6.18.
+	 */
+	if (!pdev->ltr_path)
+		info->l1ss_cap &= ~PCI_L1SS_CAP_ASPM_L1_2;
+
 	pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL1,
 			      &info->l1ss_ctl1);
 	pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL2,

drivers/pci/probe.c

@@ -554,6 +554,7 @@ struct pci_host_bridge *pci_alloc_host_bridge(size_t priv)
 	bridge->native_aer = 1;
 	bridge->native_hotplug = 1;
 	bridge->native_pme = 1;
+	bridge->native_ltr = 1;
 
 	return bridge;
 }
@@ -1954,9 +1955,13 @@ static void pci_configure_relaxed_ordering(struct pci_dev *dev)
 static void pci_configure_ltr(struct pci_dev *dev)
 {
 #ifdef CONFIG_PCIEASPM
+	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
 	u32 cap;
 	struct pci_dev *bridge;
 
+	if (!host->native_ltr)
+		return;
+
 	if (!pci_is_pcie(dev))
 		return;
 

include/linux/acpi.h

@@ -506,7 +506,8 @@ extern bool osc_pc_lpi_support_confirmed;
 #define OSC_PCI_EXPRESS_PME_CONTROL		0x00000004
 #define OSC_PCI_EXPRESS_AER_CONTROL		0x00000008
 #define OSC_PCI_EXPRESS_CAPABILITY_CONTROL	0x00000010
-#define OSC_PCI_CONTROL_MASKS			0x0000001f
+#define OSC_PCI_EXPRESS_LTR_CONTROL		0x00000020
+#define OSC_PCI_CONTROL_MASKS			0x0000003f
 
 #define ACPI_GSB_ACCESS_ATTRIB_QUICK		0x00000002
 #define ACPI_GSB_ACCESS_ATTRIB_SEND_RCV         0x00000004

include/linux/pci.h

@@ -473,6 +473,7 @@ struct pci_host_bridge {
 	unsigned int	native_aer:1;		/* OS may use PCIe AER */
 	unsigned int	native_hotplug:1;	/* OS may use PCIe hotplug */
 	unsigned int	native_pme:1;		/* OS may use PCIe PME */
+	unsigned int	native_ltr:1;		/* OS may use PCIe LTR */
 	/* Resource alignment requirements */
 	resource_size_t (*align_resource)(struct pci_dev *dev,
 			const struct resource *res,