[PATCH v13 4/6] PCI: dwc: Use common PCI host bridge APIs for finding the capabilities

[Hans Zhang]

Use the PCI core is now exposing generic macros for the host bridges to
search for the PCIe capabilities, make use of them in the DWC driver.

Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
---
Changes since v12:
- Modify the function's return value and format issues.

Changes since v11:
- Resolve compilation errors. s/dw_pcie_read_dbi/dw_pcie_read*_dbi

Changes since v10:
- None

Changes since v9:
- Resolved [v9 4/6] compilation error.
  The latest 6.15 rc1 merge __dw_pcie_find_vsec_capability, which uses 
  dw_pcie_find_next_ext_capability.

Changes since v8:
- None

Changes since v7:
- Resolve compilation errors.

Changes since v6:
https://lore.kernel.org/linux-pci/20250323164852.430546-3-18255117159@xxxxxxx/

- The patch commit message were modified.

Changes since v5:
https://lore.kernel.org/linux-pci/20250321163803.391056-3-18255117159@xxxxxxx/

- Kconfig add "select PCI_HOST_HELPERS"
---
 drivers/pci/controller/dwc/pcie-designware.c | 83 ++++----------------
 1 file changed, 16 insertions(+), 67 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 4d794964fa0f..fe3afb0d125c 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -213,83 +213,32 @@ void dw_pcie_version_detect(struct dw_pcie *pci)
 		pci->type = ver;
 }
 
-/*
- * These interfaces resemble the pci_find_*capability() interfaces, but these
- * are for configuring host controllers, which are bridges *to* PCI devices but
- * are not PCI devices themselves.
- */
-static u8 __dw_pcie_find_next_cap(struct dw_pcie *pci, u8 cap_ptr,
-				  u8 cap)
+static int dw_pcie_read_cfg(void *priv, int where, int size, u32 *val)
 {
-	u8 cap_id, next_cap_ptr;
-	u16 reg;
-
-	if (!cap_ptr)
-		return 0;
+	struct dw_pcie *pci = priv;
 
-	reg = dw_pcie_readw_dbi(pci, cap_ptr);
-	cap_id = (reg & 0x00ff);
-
-	if (cap_id > PCI_CAP_ID_MAX)
-		return 0;
-
-	if (cap_id == cap)
-		return cap_ptr;
+	if (size == 4)
+		*val = dw_pcie_readl_dbi(pci, where);
+	else if (size == 2)
+		*val = dw_pcie_readw_dbi(pci, where);
+	else if (size == 1)
+		*val = dw_pcie_readb_dbi(pci, where);
+	else
+		return PCIBIOS_BAD_REGISTER_NUMBER;
 
-	next_cap_ptr = (reg & 0xff00) >> 8;
-	return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
+	return PCIBIOS_SUCCESSFUL;
 }
 
 u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap)
 {
-	u8 next_cap_ptr;
-	u16 reg;
-
-	reg = dw_pcie_readw_dbi(pci, PCI_CAPABILITY_LIST);
-	next_cap_ptr = (reg & 0x00ff);
-
-	return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
+	return PCI_FIND_NEXT_CAP_TTL(dw_pcie_read_cfg, PCI_CAPABILITY_LIST, cap,
+				     pci);
 }
 EXPORT_SYMBOL_GPL(dw_pcie_find_capability);
 
-static u16 dw_pcie_find_next_ext_capability(struct dw_pcie *pci, u16 start,
-					    u8 cap)
-{
-	u32 header;
-	int ttl;
-	int pos = PCI_CFG_SPACE_SIZE;
-
-	/* minimum 8 bytes per capability */
-	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
-
-	if (start)
-		pos = start;
-
-	header = dw_pcie_readl_dbi(pci, pos);
-	/*
-	 * If we have no capabilities, this is indicated by cap ID,
-	 * cap version and next pointer all being 0.
-	 */
-	if (header == 0)
-		return 0;
-
-	while (ttl-- > 0) {
-		if (PCI_EXT_CAP_ID(header) == cap && pos != start)
-			return pos;
-
-		pos = PCI_EXT_CAP_NEXT(header);
-		if (pos < PCI_CFG_SPACE_SIZE)
-			break;
-
-		header = dw_pcie_readl_dbi(pci, pos);
-	}
-
-	return 0;
-}
-
 u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap)
 {
-	return dw_pcie_find_next_ext_capability(pci, 0, cap);
+	return PCI_FIND_NEXT_EXT_CAPABILITY(dw_pcie_read_cfg, 0, cap, pci);
 }
 EXPORT_SYMBOL_GPL(dw_pcie_find_ext_capability);
 
@@ -302,8 +251,8 @@ static u16 __dw_pcie_find_vsec_capability(struct dw_pcie *pci, u16 vendor_id,
 	if (vendor_id != dw_pcie_readw_dbi(pci, PCI_VENDOR_ID))
 		return 0;
 
-	while ((vsec = dw_pcie_find_next_ext_capability(pci, vsec,
-						       PCI_EXT_CAP_ID_VNDR))) {
+	while ((vsec = PCI_FIND_NEXT_EXT_CAPABILITY(dw_pcie_read_cfg, vsec,
+						    PCI_EXT_CAP_ID_VNDR, pci))) {
 		header = dw_pcie_readl_dbi(pci, vsec + PCI_VNDR_HEADER);
 		if (PCI_VNDR_HEADER_ID(header) == vsec_id)
 			return vsec;
-- 
2.25.1