Refactor pcie_tph_get_cpu_st() and add pcie_tph_get_cpu_st_ext() extended
variant with explicit requester type parameter.

- Preserve original pcie_tph_get_cpu_st() as a compatibility wrapper,
  using the default negotiated tph_max_type automatically, so existing
  callers require no modification.
- Add exported pcie_tph_get_cpu_st_ext() to accept an explicit requester
  type argument for ST namespace selection, used by upcoming VFIO TPH
  support.
- Add requester type validation to reject invalid values and enforce the
  hardware negotiated tph_max_type capability limit.

Update pci-tph.h header and CONFIG_PCIE_TPH stub inline definitions
to match the new function signatures.

Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
---
 drivers/pci/tph.c       | 45 ++++++++++++++++++++++++++++++++---------
 include/linux/pci-tph.h | 10 +++++++--
 2 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
index 1239a919b9a4..633dc6308b68 100644
--- a/drivers/pci/tph.c
+++ b/drivers/pci/tph.c
@@ -276,20 +276,22 @@ static int write_tag_to_st_table(struct pci_dev *pdev, int index, u16 tag)
 }
 
 /**
- * pcie_tph_get_cpu_st() - Retrieve Steering Tag for a target memory associated
- * with a specific CPU
+ * pcie_tph_get_cpu_st_ext() - Retrieve Steering Tag for a target memory
+ * associated with a specific CPU, with explicit requester type selection
  * @pdev: PCI device
  * @mem_type: target memory type (volatile or persistent RAM)
+ * @req_type: TPH requester type to select ST namespace
  * @cpu: 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.
+ * Return the Steering Tag for a target memory associated with a specific CPU,
+ * using the specified TPH requester type to select the correct ST namespace.
+ * Validates requester type against hardware negotiated capability limits.
  *
  * 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, u16 *tag)
+int pcie_tph_get_cpu_st_ext(struct pci_dev *pdev, enum tph_mem_type mem_type,
+			    u8 req_type, unsigned int cpu, u16 *tag)
 {
 #ifdef CONFIG_ACPI
 	struct pci_dev *rp;
@@ -298,6 +300,10 @@ int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type mem_type,
 	u32 cpu_uid;
 	int ret;
 
+	if (req_type == PCI_TPH_REQ_DISABLE || req_type == 2 ||
+		req_type > pdev->tph_max_type)
+		return -EINVAL;
+
 	ret = acpi_get_cpu_uid(cpu, &cpu_uid);
 	if (ret != 0)
 		return ret;
@@ -313,17 +319,38 @@ int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type mem_type,
 		return -EINVAL;
 	}
 
-	*tag = tph_extract_tag(mem_type, pdev->tph_req_type, &info);
+	*tag = tph_extract_tag(mem_type, req_type, &info);
 
-	pci_dbg(pdev, "get steering tag: mem_type=%s, cpu=%d, tag=%#04x\n",
+	pci_dbg(pdev, "get steering tag: mem_type=%s, req_type=%u, cpu=%d, tag=%#04x\n",
 		(mem_type == TPH_MEM_TYPE_VM) ? "volatile" : "persistent",
-		cpu, *tag);
+		req_type, cpu, *tag);
 
 	return 0;
 #else
 	return -ENODEV;
 #endif
 }
+EXPORT_SYMBOL(pcie_tph_get_cpu_st_ext);
+
+/**
+ * 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: associated CPU id
+ * @tag: Steering Tag to be returned
+ *
+ * Return the Steering Tag for a target memory associated with a specific CPU,
+ * using the default negotiated TPH requester type.
+ *
+ * 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, u16 *tag)
+{
+	return pcie_tph_get_cpu_st_ext(pdev, mem_type, pdev->tph_max_type,
+				       cpu, tag);
+}
 EXPORT_SYMBOL(pcie_tph_get_cpu_st);
 
 /**
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
index 3055776495c1..6901f6e2f8c7 100644
--- a/include/linux/pci-tph.h
+++ b/include/linux/pci-tph.h
@@ -25,8 +25,9 @@ enum tph_mem_type {
 #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,
+int pcie_tph_get_cpu_st_ext(struct pci_dev *dev, enum tph_mem_type mem_type,
+			    u8 req_type, unsigned int cpu, u16 *tag);
+int pcie_tph_get_cpu_st(struct pci_dev *dev, enum tph_mem_type mem_type,
 			unsigned int cpu, u16 *tag);
 void pcie_disable_tph(struct pci_dev *pdev);
 int pcie_enable_tph_ext(struct pci_dev *pdev, u8 mode, u8 req_type);
@@ -39,6 +40,11 @@ u8 pcie_tph_completer_type(struct pci_dev *pdev);
 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_ext(struct pci_dev *dev,
+					  enum tph_mem_type mem_type,
+					  u8 req_type, unsigned int cpu,
+					  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, u16 *tag)
-- 
2.17.1