Merge branch 'pci/capability-search'

- Simplify __pci_find_next_cap_ttl() by replacing magic numbers with
  #defines, extracting fields with FIELD_GET(), etc (Hans Zhang)

- Convert __pci_find_next_cap_ttl() to a PCI_FIND_NEXT_CAP() macro that
  takes a config space accessor function so we can also use it in cases
  where the usual config accessors aren't available (Hans Zhang)

- Similarly convert pci_find_next_ext_capability() to a
  PCI_FIND_NEXT_EXT_CAP() macro (Hans Zhang)

- Implement dwc, dwc endpoint, and cadence capability search interfaces on
  top of PCI_FIND_NEXT_CAP() and PCI_FIND_NEXT_EXT_CAP(), replacing the
  previous duplicated code (Hans Zhang)

- Search for capabilities in the cadence core instead of hard-coding their
  offsets, which are subject to change (Hans Zhang)

* pci/capability-search:
  PCI: cadence: Use cdns_pcie_find_*capability() to avoid hardcoding offsets
  PCI: cadence: Implement capability search using PCI core APIs
  PCI: dwc: ep: Implement capability search using PCI core APIs
  PCI: dwc: Implement capability search using PCI core APIs
  PCI: Refactor extended capability search into PCI_FIND_NEXT_EXT_CAP()
  PCI: Refactor capability search into PCI_FIND_NEXT_CAP()
  PCI: Clean up __pci_find_next_cap_ttl() readability

1 files changed, 85 insertions, 0 deletions

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index c1541cef82bb..4492b809094b 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -2,6 +2,8 @@
 #ifndef DRIVERS_PCI_H
 #define DRIVERS_PCI_H
 
+#include <linux/align.h>
+#include <linux/bitfield.h>
 #include <linux/pci.h>
 
 struct pcie_tlp_log;
@@ -95,6 +97,89 @@ bool pcie_cap_has_lnkctl(const struct pci_dev *dev);
 bool pcie_cap_has_lnkctl2(const struct pci_dev *dev);
 bool pcie_cap_has_rtctl(const struct pci_dev *dev);
 
+/* Standard Capability finder */
+/**
+ * PCI_FIND_NEXT_CAP - Find a PCI standard capability
+ * @read_cfg: Function pointer for reading PCI config space
+ * @start: Starting position to begin search
+ * @cap: Capability ID to find
+ * @args: Arguments to pass to read_cfg function
+ *
+ * Search the capability list in PCI config space to find @cap.
+ * Implements TTL (time-to-live) protection against infinite loops.
+ *
+ * Return: Position of the capability if found, 0 otherwise.
+ */
+#define PCI_FIND_NEXT_CAP(read_cfg, start, cap, args...)		\
+({									\
+	int __ttl = PCI_FIND_CAP_TTL;					\
+	u8 __id, __found_pos = 0;					\
+	u8 __pos = (start);						\
+	u16 __ent;							\
+									\
+	read_cfg##_byte(args, __pos, &__pos);				\
+									\
+	while (__ttl--) {						\
+		if (__pos < PCI_STD_HEADER_SIZEOF)			\
+			break;						\
+									\
+		__pos = ALIGN_DOWN(__pos, 4);				\
+		read_cfg##_word(args, __pos, &__ent);			\
+									\
+		__id = FIELD_GET(PCI_CAP_ID_MASK, __ent);		\
+		if (__id == 0xff)					\
+			break;						\
+									\
+		if (__id == (cap)) {					\
+			__found_pos = __pos;				\
+			break;						\
+		}							\
+									\
+		__pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, __ent);	\
+	}								\
+	__found_pos;							\
+})
+
+/* Extended Capability finder */
+/**
+ * PCI_FIND_NEXT_EXT_CAP - Find a PCI extended capability
+ * @read_cfg: Function pointer for reading PCI config space
+ * @start: Starting position to begin search (0 for initial search)
+ * @cap: Extended capability ID to find
+ * @args: Arguments to pass to read_cfg function
+ *
+ * Search the extended capability list in PCI config space to find @cap.
+ * Implements TTL protection against infinite loops using a calculated
+ * maximum search count.
+ *
+ * Return: Position of the capability if found, 0 otherwise.
+ */
+#define PCI_FIND_NEXT_EXT_CAP(read_cfg, start, cap, args...)		\
+({									\
+	u16 __pos = (start) ?: PCI_CFG_SPACE_SIZE;			\
+	u16 __found_pos = 0;						\
+	int __ttl, __ret;						\
+	u32 __header;							\
+									\
+	__ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;	\
+	while (__ttl-- > 0 && __pos >= PCI_CFG_SPACE_SIZE) {		\
+		__ret = read_cfg##_dword(args, __pos, &__header);	\
+		if (__ret != PCIBIOS_SUCCESSFUL)			\
+			break;						\
+									\
+		if (__header == 0)					\
+			break;						\
+									\
+		if (PCI_EXT_CAP_ID(__header) == (cap) && __pos != start) {\
+			__found_pos = __pos;				\
+			break;						\
+		}							\
+									\
+		__pos = PCI_EXT_CAP_NEXT(__header);			\
+	}								\
+	__found_pos;							\
+})
+
 /* Functions internal to the PCI core code */
 
 #ifdef CONFIG_DMI