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Commit 9bb04a0c authored by Jonathan Yong's avatar Jonathan Yong Committed by Bjorn Helgaas
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PCI: Add Precision Time Measurement (PTM) support 



Add Precision Time Measurement (PTM) support (see PCIe r3.1, sec 6.22).

Enable PTM on PTM Root devices and switch ports.  This does not enable PTM
on endpoints.

There currently are no PTM-capable devices on the market, but it is
expected to be supported by the Intel Apollo Lake platform.

[bhelgaas: complete rework]
Signed-off-by: default avatarJonathan Yong <jonathan.yong@intel.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent 29b4817d

drivers/pci/pci.h

+6 −0
Original line number Diff line number Diff line
@@ -332,6 +332,12 @@ static inline resource_size_t pci_resource_alignment(struct pci_dev *dev, 


void pci_enable_acs(struct pci_dev *dev);



#ifdef CONFIG_PCIE_PTM

void pci_ptm_init(struct pci_dev *dev);

#else

static inline void pci_ptm_init(struct pci_dev *dev) { }

#endif



struct pci_dev_reset_methods {

	u16 vendor;

	u16 device;

drivers/pci/pcie/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -92,3 +92,14 @@ config PCIE_DPC 
	  will be handled by the DPC driver.  If your system doesn't

	  have this capability or you do not want to use this feature,

	  it is safe to answer N.



config PCIE_PTM

	bool "PCIe Precision Time Measurement support"

	default n

	depends on PCIEPORTBUS

	help

	  This enables PCI Express Precision Time Measurement (PTM)

	  support.



	  This is only useful if you have devices that support PTM, but it

	  is safe to enable even if you don't.

drivers/pci/pcie/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -16,3 +16,4 @@ obj-$(CONFIG_PCIEAER) += aer/ 
obj-$(CONFIG_PCIE_PME) += pme.o



obj-$(CONFIG_PCIE_DPC) += pcie-dpc.o

obj-$(CONFIG_PCIE_PTM) += ptm.o

drivers/pci/pcie/ptm.c

0 → 100644
+70 −0
Original line number Diff line number Diff line 
/*

 * PCI Express Precision Time Measurement

 * Copyright (c) 2016, Intel Corporation.

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms and conditions of the GNU General Public License,

 * version 2, as published by the Free Software Foundation.

 *

 * This program is distributed in the hope it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for

 * more details.

 */



#include <linux/module.h>

#include <linux/init.h>

#include <linux/pci.h>

#include "../pci.h"



static void pci_ptm_info(struct pci_dev *dev)

{

	dev_info(&dev->dev, "PTM enabled%s\n", dev->ptm_root ? " (root)" : "");

}



void pci_ptm_init(struct pci_dev *dev)

{

	int pos;

	u32 cap, ctrl;

	struct pci_dev *ups;



	if (!pci_is_pcie(dev))

		return;



	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);

	if (!pos)

		return;



	/*

	 * Enable PTM only on interior devices (root ports, switch ports,

	 * etc.) on the assumption that it causes no link traffic until an

	 * endpoint enables it.

	 */

	if ((pci_pcie_type(dev) == PCI_EXP_TYPE_ENDPOINT ||

	     pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END))

		return;



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



	/*

	 * There's no point in enabling PTM unless it's enabled in the

	 * upstream device or this device can be a PTM Root itself.  Per

	 * the spec recommendation (PCIe r3.1, sec 7.32.3), select the

	 * furthest upstream Time Source as the PTM Root.

	 */

	ups = pci_upstream_bridge(dev);

	if (ups && ups->ptm_enabled) {

		ctrl = PCI_PTM_CTRL_ENABLE;

	} else {

		if (cap & PCI_PTM_CAP_ROOT) {

			ctrl = PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT;

			dev->ptm_root = 1;

		} else

			return;

	}



	pci_write_config_dword(dev, pos + PCI_PTM_CTRL, ctrl);

	dev->ptm_enabled = 1;



	pci_ptm_info(dev);

}

drivers/pci/probe.c

+3 −0
Original line number Diff line number Diff line
@@ -1667,6 +1667,9 @@ static void pci_init_capabilities(struct pci_dev *dev) 
	pci_enable_acs(dev);



	pci_cleanup_aer_error_status_regs(dev);



	/* Precision Time Measurement */

	pci_ptm_init(dev);

}



/*