From 9ab105deb60fa76d66cae5548819b4e8703d2056 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Tue, 17 Apr 2018 11:25:51 -0500 Subject: PCI/ASPM: Disable ASPM L1.2 Substate if we don't have LTR When in the ASPM L1.0 state (but not the PCI-PM L1.0 state), the most recent LTR value and the LTR_L1.2_THRESHOLD determines whether the link enters the L1.2 substate. If we don't have LTR enabled, prevent the use of ASPM L1.2. PCI-PM L1.2 may still be used because it doesn't depend on LTR_L1.2_THRESHOLD (see PCIe r4.0, sec 5.5.1). Tested-by: Srinath Mannam Signed-off-by: Bjorn Helgaas Reviewed-by: Rafael J. Wysocki --- drivers/pci/pcie/aspm.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'drivers/pci') diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index f76eb7704f64..c687c817b47d 100644 --- a/drivers/pci/pcie/aspm.c +++ b/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, -- cgit v1.2.3 From af8bb9f89838249872240f258e67774ccbcc5970 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Tue, 17 Apr 2018 10:58:09 -0500 Subject: PCI/ACPI: Request LTR control from platform before using it Per the PCI Firmware spec r3.2, sec 4.5, an ACPI-based OS should use _OSC to request control of Latency Tolerance Reporting (LTR) before using it. Request control of LTR, and if the platform does not grant control, don't use it. N.B. If the hardware supports LTR and the ASPM L1.2 substate but the BIOS doesn't support LTR in _OSC, we previously would enable ASPM L1.2. This patch will prevent us from enabling ASPM L1.2 in that case. It does not prevent us from enabling PCI-PM L1.2, since that doesn't depend on LTR. See PCIe r40, sec 5.5.1, for the L1 PM substate entry conditions. Signed-off-by: Bjorn Helgaas Reviewed-by: Rafael J. Wysocki --- drivers/acpi/pci_root.c | 6 ++++++ drivers/pci/probe.c | 5 +++++ include/linux/acpi.h | 3 ++- include/linux/pci.h | 1 + 4 files changed, 14 insertions(+), 1 deletion(-) (limited to 'drivers/pci') diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c index 0da18bde6a16..2ff0d6702a2e 100644 --- a/drivers/acpi/pci_root.c +++ b/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, diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index ac91b6fd0bcd..cc1688d75664 100644 --- a/drivers/pci/probe.c +++ b/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; diff --git a/include/linux/acpi.h b/include/linux/acpi.h index 15bfb15c2fa5..49f63c67a9d1 100644 --- a/include/linux/acpi.h +++ b/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 diff --git a/include/linux/pci.h b/include/linux/pci.h index 73178a2fcee0..d0149c01996d 100644 --- a/include/linux/pci.h +++ b/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, -- cgit v1.2.3