[PATCH V5 2/5] PCI/TPH: Add Steering Tag support

Wei Huang
2024-09-16T20:51:39Z

pcie_tph_get_cpu_st() is added to allow a caller to retrieve Steering Tags
for a target memory that is associated with a specific CPU. The ST tag is
retrieved by invoking ACPI _DSM of the device's Root Port device.

pcie_tph_set_st_entry() is added to support updating the device's Steering
Tags. The tags will be written into the device's MSI-X table or the ST
table located in the TPH Extended Capability space.

Co-developed-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
---
drivers/pci/pcie/tph.c | 339 +++++++++++++++++++++++++++++++++++++++-
include/linux/pci-tph.h | 23 +++
2 files changed, 361 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c
index 1efd76c8dd30..4b386616fc28 100644
--- a/drivers/pci/pcie/tph.c
+++ b/drivers/pci/pcie/tph.c
@@ -14,9 +14,134 @@

#include "../pci.h"

+/*
+ * The st_info struct defines the Steering Tag (ST) info returned by the
+ * firmware _DSM method defined in the approved ECN for PCI Firmware Spec,
+ * 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;
+};
+
/* System-wide TPH disabled */
static bool pci_tph_disabled;

+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;
+}
+
+/* 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;
@@ -27,6 +152,37 @@ static u8 get_st_modes(struct pci_dev *pdev)
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)
{
@@ -45,6 +201,163 @@ static u8 get_rp_completer_type(struct pci_dev *pdev)
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)
+{
+ struct msi_desc *msi_desc = NULL;
+ void __iomem *vec_ctrl;
+ u32 val, mask;
+ 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);
+ mask = PCI_MSIX_ENTRY_CTRL_ST_LOWER | PCI_MSIX_ENTRY_CTRL_ST_UPPER;
+ val &= ~mask;
+ val |= FIELD_PREP(mask, (u32)tag);
+ writel(val, vec_ctrl);
+
+ /* Read back to flush the update */
+ val = readl(vec_ctrl);
+
+err_out:
+ msi_unlock_descs(&pdev->dev);
+ return err;
+}
+
+/* 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
+ *
+ * This function returns the Steering Tag for a target memory that is
+ * associated with a specific CPU as indicated by cpu_uid.
+ *
+ * Returns: 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)
+{
+ 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;
+}
+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
+ *
+ * This function will 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.
+ *
+ * Returns: 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_* defined in pci_regs.h */
+ 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
@@ -142,6 +455,8 @@ 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)
@@ -157,11 +472,21 @@ void pci_restore_tph_state(struct pci_dev *pdev)
/* 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)
@@ -177,6 +502,16 @@ void pci_save_tph_state(struct pci_dev *pdev)
/* 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)
@@ -188,12 +523,14 @@ void pci_no_tph(void)

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;

- save_size = sizeof(u32);
+ 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);
}
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
index 58654a334ffb..c3e806c13d64 100644
--- a/include/linux/pci-tph.h
+++ b/include/linux/pci-tph.h
@@ -9,10 +9,33 @@
#ifndef LINUX_PCI_TPH_H
#define LINUX_PCI_TPH_H

+/*
+ * According to the ECN for PCI Firmware Spec, Steering Tag can be different
+ * depending on the memory type: Volatile Memory or Persistent Memory. When a
+ * caller query about a target's Steering Tag, it must provide the target's
+ * tph_mem_type. ECN link: https://members.pcisig.com/wg/PCI-SIG/document/15470.
+ */
+enum tph_mem_type {
+ TPH_MEM_TYPE_VM, /* volatile memory */
+ TPH_MEM_TYPE_PM /* persistent memory */
+};
+
#ifdef CONFIG_PCIE_TPH
+int pcie_tph_set_st_entry(struct pci_dev *pdev,
+ unsigned int index, u16 tag);
+int pcie_tph_get_cpu_st(struct pci_dev *dev,
+ enum tph_mem_type mem_type,
+ unsigned int cpu_uid, u16 *tag);
void pcie_disable_tph(struct pci_dev *pdev);
int pcie_enable_tph(struct pci_dev *pdev, int mode);
#else
+static inline int pcie_tph_set_st_entry(struct pci_dev *pdev,
+ unsigned int index, u16 tag)
+{ return -EINVAL; }
+static inline int pcie_tph_get_cpu_st(struct pci_dev *dev,
+ enum tph_mem_type mem_type,
+ unsigned int cpu_uid, u16 *tag)
+{ return -EINVAL; }
static inline void pcie_disable_tph(struct pci_dev *pdev) { }
static inline int pcie_enable_tph(struct pci_dev *pdev, int mode)
{ return -EINVAL; }
--
2.45.1