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PCI/PTM: Save/restore Precision Time Measurement Capability for suspend/resume

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The PCI subsystem does not currently save and restore the configuration
space for the Precision Time Measurement (PTM) Extended Capability leading
to the possibility of the feature returning disabled on S3 resume.  This
has been observed on Intel Coffee Lake desktops. Add save/restore of the
PTM control register. This saves the PTM Enable, Root Select, and Effective
Granularity bits.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20201207223951.19667-1-david.e.box@linux.intel.com
Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
David E. Box
2020-12-07 14:39:50 -08:00
committed by Bjorn Helgaas
parent f8394f232b
commit 39850ed510
3 changed files with 53 additions and 0 deletions
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8
drivers/pci/pci.h
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@@ -516,6 +516,14 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)
#endif /* CONFIG_PCI_IOV */
#ifdef CONFIG_PCIE_PTM
void pci_save_ptm_state(struct pci_dev *dev);
void pci_restore_ptm_state(struct pci_dev *dev);
#else
static inline void pci_save_ptm_state(struct pci_dev *dev) { }
static inline void pci_restore_ptm_state(struct pci_dev *dev) { }
#endif
unsigned long pci_cardbus_resource_alignment(struct resource *);
static inline resource_size_t pci_resource_alignment(struct pci_dev *dev,