71 lines
1.8 KiB
C
71 lines
1.8 KiB
C
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/*
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* PCI Express Precision Time Measurement
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* Copyright (c) 2016, Intel Corporation.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/pci.h>
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#include "../pci.h"
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static void pci_ptm_info(struct pci_dev *dev)
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{
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dev_info(&dev->dev, "PTM enabled%s\n", dev->ptm_root ? " (root)" : "");
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}
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void pci_ptm_init(struct pci_dev *dev)
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{
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int pos;
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u32 cap, ctrl;
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struct pci_dev *ups;
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if (!pci_is_pcie(dev))
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return;
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pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);
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if (!pos)
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return;
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/*
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* Enable PTM only on interior devices (root ports, switch ports,
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* etc.) on the assumption that it causes no link traffic until an
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* endpoint enables it.
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*/
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if ((pci_pcie_type(dev) == PCI_EXP_TYPE_ENDPOINT ||
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pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END))
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return;
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pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
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/*
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* There's no point in enabling PTM unless it's enabled in the
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* upstream device or this device can be a PTM Root itself. Per
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* the spec recommendation (PCIe r3.1, sec 7.32.3), select the
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* furthest upstream Time Source as the PTM Root.
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*/
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ups = pci_upstream_bridge(dev);
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if (ups && ups->ptm_enabled) {
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ctrl = PCI_PTM_CTRL_ENABLE;
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} else {
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if (cap & PCI_PTM_CAP_ROOT) {
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ctrl = PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT;
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dev->ptm_root = 1;
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} else
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return;
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}
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pci_write_config_dword(dev, pos + PCI_PTM_CTRL, ctrl);
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dev->ptm_enabled = 1;
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pci_ptm_info(dev);
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}
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