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PCI: Add pci_enable_ptm() for drivers to enable PTM on endpoints

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Add an pci_enable_ptm() interface so drivers can enable PTM.

The PCI core enables PTM on PTM Roots and switches automatically, but we
don't enable PTM on endpoints unless a driver requests it.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Bjorn Helgaas
2016-06-13 11:01:51 -05:00
parent 9bb04a0c4e
commit eec097d431
3 changed files with 53 additions and 0 deletions
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45
drivers/pci/pcie/ptm.c
View File

@@ -68,3 +68,48 @@ void pci_ptm_init(struct pci_dev *dev)
pci_ptm_info(dev);
}
int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
{
int pos;
u32 cap, ctrl;
struct pci_dev *ups;
if (!pci_is_pcie(dev))
return -EINVAL;
pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);
if (!pos)
return -EINVAL;
pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
if (!(cap & PCI_PTM_CAP_REQ))
return -EINVAL;
/*
* For a PCIe Endpoint, PTM is only useful if the endpoint can
* issue PTM requests to upstream devices that have PTM enabled.
*
* For Root Complex Integrated Endpoints, there is no upstream
* device, so there must be some implementation-specific way to
* associate the endpoint with a time source.
*/
if (pci_pcie_type(dev) == PCI_EXP_TYPE_ENDPOINT) {
ups = pci_upstream_bridge(dev);
if (!ups || !ups->ptm_enabled)
return -EINVAL;
} else if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
} else
return -EINVAL;
ctrl = PCI_PTM_CTRL_ENABLE;
pci_write_config_dword(dev, pos + PCI_PTM_CTRL, ctrl);
dev->ptm_enabled = 1;
pci_ptm_info(dev);
if (granularity)
*granularity = 0;
return 0;
}
EXPORT_SYMBOL(pci_enable_ptm);