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PCI/ASPM: Enable Latency Tolerance Reporting when supported

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Enable Latency Tolerance Reporting (LTR).  Note that LTR must be enabled in
the Root Port first, and must not be enabled in any downstream device
unless the Root Port and all intermediate Switches also support LTR.
See PCIe r3.1, sec 6.18.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Vidya Sagar <vidyas@nvidia.com>
This commit is contained in:
Bjorn Helgaas 2017-11-28 16:43:50 -06:00
parent 80d7d7a904
commit c46fd35807
2 changed files with 35 additions and 0 deletions
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33
drivers/pci/probe.c
View file

@ -1875,6 +1875,38 @@ static void pci_configure_relaxed_ordering(struct pci_dev *dev)
}
}
static void pci_configure_ltr(struct pci_dev *dev)
{
#ifdef CONFIG_PCIEASPM
u32 cap;
struct pci_dev *bridge;
if (!pci_is_pcie(dev))
return;
pcie_capability_read_dword(dev, PCI_EXP_DEVCAP2, &cap);
if (!(cap & PCI_EXP_DEVCAP2_LTR))
return;
/*
* Software must not enable LTR in an Endpoint unless the Root
* Complex and all intermediate Switches indicate support for LTR.
* PCIe r3.1, sec 6.18.
*/
if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
dev->ltr_path = 1;
else {
bridge = pci_upstream_bridge(dev);
if (bridge && bridge->ltr_path)
dev->ltr_path = 1;
}
if (dev->ltr_path)
pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,
PCI_EXP_DEVCTL2_LTR_EN);
#endif
}
static void pci_configure_device(struct pci_dev *dev)
{
struct hotplug_params hpp;
@ -1883,6 +1915,7 @@ static void pci_configure_device(struct pci_dev *dev)
pci_configure_mps(dev);
pci_configure_extended_tags(dev, NULL);
pci_configure_relaxed_ordering(dev);
pci_configure_ltr(dev);
memset(&hpp, 0, sizeof(hpp));
ret = pci_get_hp_params(dev, &hpp);

2
include/linux/pci.h
View file

@ -350,6 +350,8 @@ struct pci_dev {
#ifdef CONFIG_PCIEASPM
struct pcie_link_state *link_state; /* ASPM link state */
unsigned int ltr_path:1; /* Latency Tolerance Reporting
supported from root to here */
#endif
pci_channel_state_t error_state; /* current connectivity state */