Merge branch 'pci/tph'

- Add and document TLP Processing Hints (TPH) support so drivers can enable
  and disable TPH and the kernel can save/restore TPH configuration (Wei
  Huang)

- Add TPH Steering Tag support so drivers can retrieve Steering Tag values
  associated with specific CPUs via an ACPI _DSM to direct DMA writes
  closer to their consumers (Wei Huang)

* pci/tph:
  PCI/TPH: Add TPH documentation
  PCI/TPH: Add Steering Tag support
  PCI: Add TLP Processing Hints (TPH) support

6 files changed, 574 insertions, 0 deletions

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index e1c025698a28..2fbd379923fd 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -173,6 +173,15 @@ config PCI_PASID
 
 	  If unsure, say N.
 
+config PCIE_TPH
+	bool "TLP Processing Hints"
+	help
+	  This option adds support for PCIe TLP Processing Hints (TPH).
+	  TPH allows endpoint devices to provide optimization hints, such as
+	  desired caching behavior, for requests that target memory space.
+	  These hints, called Steering Tags, can empower the system hardware
+	  to optimize the utilization of platform resources.
+
 config PCI_P2PDMA
 	bool "PCI peer-to-peer transfer support"
 	depends on ZONE_DEVICE
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 39a07890abd1..67647f1880fb 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_VGA_ARB)		+= vgaarb.o
 obj-$(CONFIG_PCI_DOE)		+= doe.o
 obj-$(CONFIG_PCI_DYNAMIC_OF_NODES) += of_property.o
 obj-$(CONFIG_PCI_NPEM)		+= npem.o
+obj-$(CONFIG_PCIE_TPH)		+= tph.o
 
 # Endpoint library must be initialized before its users
 obj-$(CONFIG_PCI_ENDPOINT)	+= endpoint/
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 880f7565acf3..43c9a0e029c9 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1828,6 +1828,7 @@ int pci_save_state(struct pci_dev *dev)
 	pci_save_dpc_state(dev);
 	pci_save_aer_state(dev);
 	pci_save_ptm_state(dev);
+	pci_save_tph_state(dev);
 	return pci_save_vc_state(dev);
 }
 EXPORT_SYMBOL(pci_save_state);
@@ -1933,6 +1934,7 @@ void pci_restore_state(struct pci_dev *dev)
 	pci_restore_rebar_state(dev);
 	pci_restore_dpc_state(dev);
 	pci_restore_ptm_state(dev);
+	pci_restore_tph_state(dev);
 
 	pci_aer_clear_status(dev);
 	pci_restore_aer_state(dev);
@@ -6925,6 +6927,8 @@ static int __init pci_setup(char *str)
 				pci_no_domains();
 			} else if (!strncmp(str, "noari", 5)) {
 				pcie_ari_disabled = true;
+			} else if (!strncmp(str, "notph", 5)) {
+				pci_no_tph();
 			} else if (!strncmp(str, "cbiosize=", 9)) {
 				pci_cardbus_io_size = memparse(str + 9, &str);
 			} else if (!strncmp(str, "cbmemsize=", 10)) {
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 7531e4b005c6..2e40fc63ba31 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -638,6 +638,18 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)
 
 #endif /* CONFIG_PCI_IOV */
 
+#ifdef CONFIG_PCIE_TPH
+void pci_restore_tph_state(struct pci_dev *dev);
+void pci_save_tph_state(struct pci_dev *dev);
+void pci_no_tph(void);
+void pci_tph_init(struct pci_dev *dev);
+#else
+static inline void pci_restore_tph_state(struct pci_dev *dev) { }
+static inline void pci_save_tph_state(struct pci_dev *dev) { }
+static inline void pci_no_tph(void) { }
+static inline void pci_tph_init(struct pci_dev *dev) { }
+#endif
+
 #ifdef CONFIG_PCIE_PTM
 void pci_ptm_init(struct pci_dev *dev);
 void pci_save_ptm_state(struct pci_dev *dev);
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8a7e58e20839..bf4c76ec8cd4 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2516,6 +2516,7 @@ static void pci_init_capabilities(struct pci_dev *dev)
 	pci_dpc_init(dev);		/* Downstream Port Containment */
 	pci_rcec_init(dev);		/* Root Complex Event Collector */
 	pci_doe_init(dev);		/* Data Object Exchange */
+	pci_tph_init(dev);		/* TLP Processing Hints */
 
 	pcie_report_downtraining(dev);
 	pci_init_reset_methods(dev);
diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
new file mode 100644
index 000000000000..1e604fbbda65
--- /dev/null
+++ b/drivers/pci/tph.c
@@ -0,0 +1,547 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TPH (TLP Processing Hints) support
+ *
+ * Copyright (C) 2024 Advanced Micro Devices, Inc.
+ *     Eric Van Tassell <Eric.VanTassell@amd.com>
+ *     Wei Huang <wei.huang2@amd.com>
+ */
+#include <linux/pci.h>
+#include <linux/pci-acpi.h>
+#include <linux/msi.h>
+#include <linux/bitfield.h>
+#include <linux/pci-tph.h>
+
+#include "pci.h"
+
+/* System-wide TPH disabled */
+static bool pci_tph_disabled;
+
+#ifdef CONFIG_ACPI
+/*
+ * The st_info struct defines the Steering Tag (ST) info returned by the
+ * firmware PCI ACPI _DSM method (rev=0x7, func=0xF, "_DSM to Query Cache
+ * Locality TPH Features"), as specified in the approved ECN for PCI Firmware
+ * Spec and available at https://members.pcisig.com/wg/PCI-SIG/document/15470.
+ *
+ * @vm_st_valid:  8-bit ST for volatile memory is valid
+ * @vm_xst_valid: 16-bit extended ST for volatile memory is valid
+ * @vm_ph_ignore: 1 => PH was and will be ignored, 0 => PH should be supplied
+ * @vm_st:        8-bit ST for volatile mem
+ * @vm_xst:       16-bit extended ST for volatile mem
+ * @pm_st_valid:  8-bit ST for persistent memory is valid
+ * @pm_xst_valid: 16-bit extended ST for persistent memory is valid
+ * @pm_ph_ignore: 1 => PH was and will be ignored, 0 => PH should be supplied
+ * @pm_st:        8-bit ST for persistent mem
+ * @pm_xst:       16-bit extended ST for persistent mem
+ */
+union st_info {
+	struct {
+		u64 vm_st_valid : 1;
+		u64 vm_xst_valid : 1;
+		u64 vm_ph_ignore : 1;
+		u64 rsvd1 : 5;
+		u64 vm_st : 8;
+		u64 vm_xst : 16;
+		u64 pm_st_valid : 1;
+		u64 pm_xst_valid : 1;
+		u64 pm_ph_ignore : 1;
+		u64 rsvd2 : 5;
+		u64 pm_st : 8;
+		u64 pm_xst : 16;
+	};
+	u64 value;
+};
+
+static u16 tph_extract_tag(enum tph_mem_type mem_type, u8 req_type,
+			   union st_info *info)
+{
+	switch (req_type) {
+	case PCI_TPH_REQ_TPH_ONLY: /* 8-bit tag */
+		switch (mem_type) {
+		case TPH_MEM_TYPE_VM:
+			if (info->vm_st_valid)
+				return info->vm_st;
+			break;
+		case TPH_MEM_TYPE_PM:
+			if (info->pm_st_valid)
+				return info->pm_st;
+			break;
+		}
+		break;
+	case PCI_TPH_REQ_EXT_TPH: /* 16-bit tag */
+		switch (mem_type) {
+		case TPH_MEM_TYPE_VM:
+			if (info->vm_xst_valid)
+				return info->vm_xst;
+			break;
+		case TPH_MEM_TYPE_PM:
+			if (info->pm_xst_valid)
+				return info->pm_xst;
+			break;
+		}
+		break;
+	default:
+		return 0;
+	}
+
+	return 0;
+}
+
+#define TPH_ST_DSM_FUNC_INDEX	0xF
+static acpi_status tph_invoke_dsm(acpi_handle handle, u32 cpu_uid,
+				  union st_info *st_out)
+{
+	union acpi_object arg3[3], in_obj, *out_obj;
+
+	if (!acpi_check_dsm(handle, &pci_acpi_dsm_guid, 7,
+			    BIT(TPH_ST_DSM_FUNC_INDEX)))
+		return AE_ERROR;
+
+	/* DWORD: feature ID (0 for processor cache ST query) */
+	arg3[0].integer.type = ACPI_TYPE_INTEGER;
+	arg3[0].integer.value = 0;
+
+	/* DWORD: target UID */
+	arg3[1].integer.type = ACPI_TYPE_INTEGER;
+	arg3[1].integer.value = cpu_uid;
+
+	/* QWORD: properties, all 0's */
+	arg3[2].integer.type = ACPI_TYPE_INTEGER;
+	arg3[2].integer.value = 0;
+
+	in_obj.type = ACPI_TYPE_PACKAGE;
+	in_obj.package.count = ARRAY_SIZE(arg3);
+	in_obj.package.elements = arg3;
+
+	out_obj = acpi_evaluate_dsm(handle, &pci_acpi_dsm_guid, 7,
+				    TPH_ST_DSM_FUNC_INDEX, &in_obj);
+	if (!out_obj)
+		return AE_ERROR;
+
+	if (out_obj->type != ACPI_TYPE_BUFFER) {
+		ACPI_FREE(out_obj);
+		return AE_ERROR;
+	}
+
+	st_out->value = *((u64 *)(out_obj->buffer.pointer));
+
+	ACPI_FREE(out_obj);
+
+	return AE_OK;
+}
+#endif
+
+/* Update the TPH Requester Enable field of TPH Control Register */
+static void set_ctrl_reg_req_en(struct pci_dev *pdev, u8 req_type)
+{
+	u32 reg;
+
+	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, &reg);
+
+	reg &= ~PCI_TPH_CTRL_REQ_EN_MASK;
+	reg |= FIELD_PREP(PCI_TPH_CTRL_REQ_EN_MASK, req_type);
+
+	pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, reg);
+}
+
+static u8 get_st_modes(struct pci_dev *pdev)
+{
+	u32 reg;
+
+	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+	reg &= PCI_TPH_CAP_ST_NS | PCI_TPH_CAP_ST_IV | PCI_TPH_CAP_ST_DS;
+
+	return reg;
+}
+
+static u32 get_st_table_loc(struct pci_dev *pdev)
+{
+	u32 reg;
+
+	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+
+	return FIELD_GET(PCI_TPH_CAP_LOC_MASK, reg);
+}
+
+/*
+ * Return the size of ST table. If ST table is not in TPH Requester Extended
+ * Capability space, return 0. Otherwise return the ST Table Size + 1.
+ */
+static u16 get_st_table_size(struct pci_dev *pdev)
+{
+	u32 reg;
+	u32 loc;
+
+	/* Check ST table location first */
+	loc = get_st_table_loc(pdev);
+
+	/* Convert loc to match with PCI_TPH_LOC_* defined in pci_regs.h */
+	loc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);
+	if (loc != PCI_TPH_LOC_CAP)
+		return 0;
+
+	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+
+	return FIELD_GET(PCI_TPH_CAP_ST_MASK, reg) + 1;
+}
+
+/* Return device's Root Port completer capability */
+static u8 get_rp_completer_type(struct pci_dev *pdev)
+{
+	struct pci_dev *rp;
+	u32 reg;
+	int ret;
+
+	rp = pcie_find_root_port(pdev);
+	if (!rp)
+		return 0;
+
+	ret = pcie_capability_read_dword(rp, PCI_EXP_DEVCAP2, &reg);
+	if (ret)
+		return 0;
+
+	return FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg);
+}
+
+/* Write ST to MSI-X vector control reg - Return 0 if OK, otherwise -errno */
+static int write_tag_to_msix(struct pci_dev *pdev, int msix_idx, u16 tag)
+{
+#ifdef CONFIG_PCI_MSI
+	struct msi_desc *msi_desc = NULL;
+	void __iomem *vec_ctrl;
+	u32 val;
+	int err = 0;
+
+	msi_lock_descs(&pdev->dev);
+
+	/* Find the msi_desc entry with matching msix_idx */
+	msi_for_each_desc(msi_desc, &pdev->dev, MSI_DESC_ASSOCIATED) {
+		if (msi_desc->msi_index == msix_idx)
+			break;
+	}
+
+	if (!msi_desc) {
+		err = -ENXIO;
+		goto err_out;
+	}
+
+	/* Get the vector control register (offset 0xc) pointed by msix_idx */
+	vec_ctrl = pdev->msix_base + msix_idx * PCI_MSIX_ENTRY_SIZE;
+	vec_ctrl += PCI_MSIX_ENTRY_VECTOR_CTRL;
+
+	val = readl(vec_ctrl);
+	val &= ~PCI_MSIX_ENTRY_CTRL_ST;
+	val |= FIELD_PREP(PCI_MSIX_ENTRY_CTRL_ST, tag);
+	writel(val, vec_ctrl);
+
+	/* Read back to flush the update */
+	val = readl(vec_ctrl);
+
+err_out:
+	msi_unlock_descs(&pdev->dev);
+	return err;
+#else
+	return -ENODEV;
+#endif
+}
+
+/* Write tag to ST table - Return 0 if OK, otherwise -errno */
+static int write_tag_to_st_table(struct pci_dev *pdev, int index, u16 tag)
+{
+	int st_table_size;
+	int offset;
+
+	/* Check if index is out of bound */
+	st_table_size = get_st_table_size(pdev);
+	if (index >= st_table_size)
+		return -ENXIO;
+
+	offset = pdev->tph_cap + PCI_TPH_BASE_SIZEOF + index * sizeof(u16);
+
+	return pci_write_config_word(pdev, offset, tag);
+}
+
+/**
+ * pcie_tph_get_cpu_st() - Retrieve Steering Tag for a target memory associated
+ * with a specific CPU
+ * @pdev: PCI device
+ * @mem_type: target memory type (volatile or persistent RAM)
+ * @cpu_uid: associated CPU id
+ * @tag: Steering Tag to be returned
+ *
+ * Return the Steering Tag for a target memory that is associated with a
+ * specific CPU as indicated by cpu_uid.
+ *
+ * Return: 0 if success, otherwise negative value (-errno)
+ */
+int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type mem_type,
+			unsigned int cpu_uid, u16 *tag)
+{
+#ifdef CONFIG_ACPI
+	struct pci_dev *rp;
+	acpi_handle rp_acpi_handle;
+	union st_info info;
+
+	rp = pcie_find_root_port(pdev);
+	if (!rp || !rp->bus || !rp->bus->bridge)
+		return -ENODEV;
+
+	rp_acpi_handle = ACPI_HANDLE(rp->bus->bridge);
+
+	if (tph_invoke_dsm(rp_acpi_handle, cpu_uid, &info) != AE_OK) {
+		*tag = 0;
+		return -EINVAL;
+	}
+
+	*tag = tph_extract_tag(mem_type, pdev->tph_req_type, &info);
+
+	pci_dbg(pdev, "get steering tag: mem_type=%s, cpu_uid=%d, tag=%#04x\n",
+		(mem_type == TPH_MEM_TYPE_VM) ? "volatile" : "persistent",
+		cpu_uid, *tag);
+
+	return 0;
+#else
+	return -ENODEV;
+#endif
+}
+EXPORT_SYMBOL(pcie_tph_get_cpu_st);
+
+/**
+ * pcie_tph_set_st_entry() - Set Steering Tag in the ST table entry
+ * @pdev: PCI device
+ * @index: ST table entry index
+ * @tag: Steering Tag to be written
+ *
+ * Figure out the proper location of ST table, either in the MSI-X table or
+ * in the TPH Extended Capability space, and write the Steering Tag into
+ * the ST entry pointed by index.
+ *
+ * Return: 0 if success, otherwise negative value (-errno)
+ */
+int pcie_tph_set_st_entry(struct pci_dev *pdev, unsigned int index, u16 tag)
+{
+	u32 loc;
+	int err = 0;
+
+	if (!pdev->tph_cap)
+		return -EINVAL;
+
+	if (!pdev->tph_enabled)
+		return -EINVAL;
+
+	/* No need to write tag if device is in "No ST Mode" */
+	if (pdev->tph_mode == PCI_TPH_ST_NS_MODE)
+		return 0;
+
+	/*
+	 * Disable TPH before updating ST to avoid potential instability as
+	 * cautioned in PCIe r6.2, sec 6.17.3, "ST Modes of Operation"
+	 */
+	set_ctrl_reg_req_en(pdev, PCI_TPH_REQ_DISABLE);
+
+	loc = get_st_table_loc(pdev);
+	/* Convert loc to match with PCI_TPH_LOC_* */
+	loc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);
+
+	switch (loc) {
+	case PCI_TPH_LOC_MSIX:
+		err = write_tag_to_msix(pdev, index, tag);
+		break;
+	case PCI_TPH_LOC_CAP:
+		err = write_tag_to_st_table(pdev, index, tag);
+		break;
+	default:
+		err = -EINVAL;
+	}
+
+	if (err) {
+		pcie_disable_tph(pdev);
+		return err;
+	}
+
+	set_ctrl_reg_req_en(pdev, pdev->tph_mode);
+
+	pci_dbg(pdev, "set steering tag: %s table, index=%d, tag=%#04x\n",
+		(loc == PCI_TPH_LOC_MSIX) ? "MSI-X" : "ST", index, tag);
+
+	return 0;
+}
+EXPORT_SYMBOL(pcie_tph_set_st_entry);
+
+/**
+ * pcie_disable_tph - Turn off TPH support for device
+ * @pdev: PCI device
+ *
+ * Return: none
+ */
+void pcie_disable_tph(struct pci_dev *pdev)
+{
+	if (!pdev->tph_cap)
+		return;
+
+	if (!pdev->tph_enabled)
+		return;
+
+	pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, 0);
+
+	pdev->tph_mode = 0;
+	pdev->tph_req_type = 0;
+	pdev->tph_enabled = 0;
+}
+EXPORT_SYMBOL(pcie_disable_tph);
+
+/**
+ * pcie_enable_tph - Enable TPH support for device using a specific ST mode
+ * @pdev: PCI device
+ * @mode: ST mode to enable. Current supported modes include:
+ *
+ *   - PCI_TPH_ST_NS_MODE: NO ST Mode
+ *   - PCI_TPH_ST_IV_MODE: Interrupt Vector Mode
+ *   - PCI_TPH_ST_DS_MODE: Device Specific Mode
+ *
+ * Check whether the mode is actually supported by the device before enabling
+ * and return an error if not. Additionally determine what types of requests,
+ * TPH or extended TPH, can be issued by the device based on its TPH requester
+ * capability and the Root Port's completer capability.
+ *
+ * Return: 0 on success, otherwise negative value (-errno)
+ */
+int pcie_enable_tph(struct pci_dev *pdev, int mode)
+{
+	u32 reg;
+	u8 dev_modes;
+	u8 rp_req_type;
+
+	/* Honor "notph" kernel parameter */
+	if (pci_tph_disabled)
+		return -EINVAL;
+
+	if (!pdev->tph_cap)
+		return -EINVAL;
+
+	if (pdev->tph_enabled)
+		return -EBUSY;
+
+	/* Sanitize and check ST mode compatibility */
+	mode &= PCI_TPH_CTRL_MODE_SEL_MASK;
+	dev_modes = get_st_modes(pdev);
+	if (!((1 << mode) & dev_modes))
+		return -EINVAL;
+
+	pdev->tph_mode = mode;
+
+	/* Get req_type supported by device and its Root Port */
+	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+	if (FIELD_GET(PCI_TPH_CAP_EXT_TPH, reg))
+		pdev->tph_req_type = PCI_TPH_REQ_EXT_TPH;
+	else
+		pdev->tph_req_type = PCI_TPH_REQ_TPH_ONLY;
+
+	rp_req_type = get_rp_completer_type(pdev);
+
+	/* Final req_type is the smallest value of two */
+	pdev->tph_req_type = min(pdev->tph_req_type, rp_req_type);
+
+	if (pdev->tph_req_type == PCI_TPH_REQ_DISABLE)
+		return -EINVAL;
+
+	/* Write them into TPH control register */
+	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, &reg);
+
+	reg &= ~PCI_TPH_CTRL_MODE_SEL_MASK;
+	reg |= FIELD_PREP(PCI_TPH_CTRL_MODE_SEL_MASK, pdev->tph_mode);
+
+	reg &= ~PCI_TPH_CTRL_REQ_EN_MASK;
+	reg |= FIELD_PREP(PCI_TPH_CTRL_REQ_EN_MASK, pdev->tph_req_type);
+
+	pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, reg);
+
+	pdev->tph_enabled = 1;
+
+	return 0;
+}
+EXPORT_SYMBOL(pcie_enable_tph);
+
+void pci_restore_tph_state(struct pci_dev *pdev)
+{
+	struct pci_cap_saved_state *save_state;
+	int num_entries, i, offset;
+	u16 *st_entry;
+	u32 *cap;
+
+	if (!pdev->tph_cap)
+		return;
+
+	if (!pdev->tph_enabled)
+		return;
+
+	save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_TPH);
+	if (!save_state)
+		return;
+
+	/* Restore control register and all ST entries */
+	cap = &save_state->cap.data[0];
+	pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, *cap++);
+	st_entry = (u16 *)cap;
+	offset = PCI_TPH_BASE_SIZEOF;
+	num_entries = get_st_table_size(pdev);
+	for (i = 0; i < num_entries; i++) {
+		pci_write_config_word(pdev, pdev->tph_cap + offset,
+				      *st_entry++);
+		offset += sizeof(u16);
+	}
+}
+
+void pci_save_tph_state(struct pci_dev *pdev)
+{
+	struct pci_cap_saved_state *save_state;
+	int num_entries, i, offset;
+	u16 *st_entry;
+	u32 *cap;
+
+	if (!pdev->tph_cap)
+		return;
+
+	if (!pdev->tph_enabled)
+		return;
+
+	save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_TPH);
+	if (!save_state)
+		return;
+
+	/* Save control register */
+	cap = &save_state->cap.data[0];
+	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, cap++);
+
+	/* Save all ST entries in extended capability structure */
+	st_entry = (u16 *)cap;
+	offset = PCI_TPH_BASE_SIZEOF;
+	num_entries = get_st_table_size(pdev);
+	for (i = 0; i < num_entries; i++) {
+		pci_read_config_word(pdev, pdev->tph_cap + offset,
+				     st_entry++);
+		offset += sizeof(u16);
+	}
+}
+
+void pci_no_tph(void)
+{
+	pci_tph_disabled = true;
+
+	pr_info("PCIe TPH is disabled\n");
+}
+
+void pci_tph_init(struct pci_dev *pdev)
+{
+	int num_entries;
+	u32 save_size;
+
+	pdev->tph_cap = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_TPH);
+	if (!pdev->tph_cap)
+		return;
+
+	num_entries = get_st_table_size(pdev);
+	save_size = sizeof(u32) + num_entries * sizeof(u16);
+	pci_add_ext_cap_save_buffer(pdev, PCI_EXT_CAP_ID_TPH, save_size);
+}