[PATCH v13 2/5] PCI/TPH: Add requester/completer type helpers

Add pcie_tph_enabled_req_type() so drivers can query the enabled TPH
requester mode without reaching into pci_dev internals.

Add pcie_tph_completer_type() so drivers that publish TPH metadata for a
device acting as a completer can gate on the "TPH Completer Supported"
field of Device Capabilities 2 (bits 13:12, PCI_EXP_DEVCAP2_TPH_COMP_MASK)
rather than reusing requester-side state. It applies the same reserved-
encoding fold as get_rp_completer_type(), inlined, so the reserved 0b10
value never reaches callers.

This keeps pci_dev::tph_req_type and the completer-capability decode
inside the PCI/TPH code and provides !CONFIG_PCIE_TPH stubs for callers.

Signed-off-by: Zhiping Zhang <[email protected]>
---
 drivers/pci/tph.c       | 44 +++++++++++++++++++++++++++++++++++++++++
 include/linux/pci-tph.h |  8 ++++++++
 2 files changed, 52 insertions(+)

diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
index 5cbb381e2a02..d0202ff7a1b2 100644
--- a/drivers/pci/tph.c
+++ b/drivers/pci/tph.c
@@ -223,6 +223,50 @@ static u8 get_rp_completer_type(struct pci_dev *pdev)
 	return PCI_EXP_DEVCAP2_TPH_COMP_NONE;
 }
 
+/**
+ * pcie_tph_enabled_req_type - Return the device's enabled TPH requester type
+ * @pdev: PCI device to query
+ *
+ * Return: PCI_TPH_REQ_DISABLE, PCI_TPH_REQ_TPH_ONLY or PCI_TPH_REQ_EXT_TPH.
+ */
+u8 pcie_tph_enabled_req_type(struct pci_dev *pdev)
+{
+	return pdev->tph_req_type;
+}
+EXPORT_SYMBOL(pcie_tph_enabled_req_type);
+
+/**
+ * pcie_tph_completer_type - Return the device's TPH Completer support
+ * @pdev: PCI device to query
+ *
+ * Reads the "TPH Completer Supported" field (bits 13:12) of Device
+ * Capabilities 2. The reserved 0b10 encoding is folded into
+ * "not supported" so callers only need to compare against the three
+ * defined values.
+ *
+ * Return: one of %PCI_EXP_DEVCAP2_TPH_COMP_NONE,
+ *         %PCI_EXP_DEVCAP2_TPH_COMP_TPH_ONLY or
+ *         %PCI_EXP_DEVCAP2_TPH_COMP_EXT_TPH.
+ */
+u8 pcie_tph_completer_type(struct pci_dev *pdev)
+{
+	u8 tph_comp;
+	u32 reg;
+
+	if (pcie_capability_read_dword(pdev, PCI_EXP_DEVCAP2, &reg))
+		return PCI_EXP_DEVCAP2_TPH_COMP_NONE;
+	if (PCI_POSSIBLE_ERROR(reg))
+		return PCI_EXP_DEVCAP2_TPH_COMP_NONE;
+
+	/* 0b10 is reserved; fold it into "not supported" (see above). */
+	tph_comp = FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg);
+	if (tph_comp == PCI_EXP_DEVCAP2_TPH_COMP_TPH_ONLY ||
+	    tph_comp == PCI_EXP_DEVCAP2_TPH_COMP_EXT_TPH)
+		return tph_comp;
+	return PCI_EXP_DEVCAP2_TPH_COMP_NONE;
+}
+EXPORT_SYMBOL(pcie_tph_completer_type);
+
 /* 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)
 {
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
index be68cd17f2f8..7743af6fe432 100644
--- a/include/linux/pci-tph.h
+++ b/include/linux/pci-tph.h
@@ -9,6 +9,8 @@
 #ifndef LINUX_PCI_TPH_H
 #define LINUX_PCI_TPH_H
 
+#include <linux/pci_regs.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
@@ -30,6 +32,8 @@ void pcie_disable_tph(struct pci_dev *pdev);
 int pcie_enable_tph(struct pci_dev *pdev, int mode);
 u16 pcie_tph_get_st_table_size(struct pci_dev *pdev);
 u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev);
+u8 pcie_tph_enabled_req_type(struct pci_dev *pdev);
+u8 pcie_tph_completer_type(struct pci_dev *pdev);
 #else
 static inline int pcie_tph_set_st_entry(struct pci_dev *pdev,
 					unsigned int index, u16 tag)
@@ -41,6 +45,10 @@ static inline int pcie_tph_get_cpu_st(struct pci_dev *dev,
 static inline void pcie_disable_tph(struct pci_dev *pdev) { }
 static inline int pcie_enable_tph(struct pci_dev *pdev, int mode)
 { return -EINVAL; }
+static inline u8 pcie_tph_enabled_req_type(struct pci_dev *pdev)
+{ return PCI_TPH_REQ_DISABLE; }
+static inline u8 pcie_tph_completer_type(struct pci_dev *pdev)
+{ return PCI_EXP_DEVCAP2_TPH_COMP_NONE; }
 #endif
 
 #endif /* LINUX_PCI_TPH_H */
-- 
2.53.0-Meta