Commit 39850ed5 authored by David E. Box's avatar David E. Box Committed by Bjorn Helgaas
Browse files

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



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: default avatarRafael 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: default avatarDavid E. Box <david.e.box@linux.intel.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent f8394f23

drivers/pci/pci.c

+2 −0
Original line number Diff line number Diff line
@@ -1566,6 +1566,7 @@ int pci_save_state(struct pci_dev *dev) 
	pci_save_ltr_state(dev);

	pci_save_dpc_state(dev);

	pci_save_aer_state(dev);

	pci_save_ptm_state(dev);

	return pci_save_vc_state(dev);

}

EXPORT_SYMBOL(pci_save_state);
@@ -1677,6 +1678,7 @@ void pci_restore_state(struct pci_dev *dev) 
	pci_restore_vc_state(dev);

	pci_restore_rebar_state(dev);

	pci_restore_dpc_state(dev);

	pci_restore_ptm_state(dev);



	pci_aer_clear_status(dev);

	pci_restore_aer_state(dev);

drivers/pci/pci.h

+8 −0
Original line number Diff line number Diff line
@@ -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,

drivers/pci/pcie/ptm.c

+43 −0
Original line number Diff line number Diff line
@@ -29,6 +29,47 @@ static void pci_ptm_info(struct pci_dev *dev) 
		 dev->ptm_root ? " (root)" : "", clock_desc);

}



void pci_save_ptm_state(struct pci_dev *dev)

{

	int ptm;

	struct pci_cap_saved_state *save_state;

	u16 *cap;



	if (!pci_is_pcie(dev))

		return;



	ptm = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);

	if (!ptm)

		return;



	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);

	if (!save_state) {

		pci_err(dev, "no suspend buffer for PTM\n");

		return;

	}



	cap = (u16 *)&save_state->cap.data[0];

	pci_read_config_word(dev, ptm + PCI_PTM_CTRL, cap);

}



void pci_restore_ptm_state(struct pci_dev *dev)

{

	struct pci_cap_saved_state *save_state;

	int ptm;

	u16 *cap;



	if (!pci_is_pcie(dev))

		return;



	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);

	ptm = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);

	if (!save_state || !ptm)

		return;



	cap = (u16 *)&save_state->cap.data[0];

	pci_write_config_word(dev, ptm + PCI_PTM_CTRL, *cap);

}



void pci_ptm_init(struct pci_dev *dev)

{

	int pos;
@@ -65,6 +106,8 @@ void pci_ptm_init(struct pci_dev *dev) 
	if (!pos)

		return;



	pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_PTM, sizeof(u16));



	pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);

	local_clock = (cap & PCI_PTM_GRANULARITY_MASK) >> 8;