PCI: dwc: ep: Implement capability search using PCI core APIs

The PCI core now provides generic PCI_FIND_NEXT_CAP() macros to search for
PCI capabilities, using config accessors we supply.

Use them in the DWC EP driver to implement dw_pcie_ep_find_capability()
instead of duplicating the algorithm.

Signed-off-by: Hans Zhang <18255117159@163.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250819145828.438541-1-18255117159@163.com

Author: Hans Zhang

drivers/pci/controller/dwc/pcie-designware-ep.c

@@ -69,37 +69,10 @@ void dw_pcie_ep_reset_bar(struct dw_pcie *pci, enum pci_barno bar)
 }
 EXPORT_SYMBOL_GPL(dw_pcie_ep_reset_bar);
 
-static u8 __dw_pcie_ep_find_next_cap(struct dw_pcie_ep *ep, u8 func_no,
-				     u8 cap_ptr, u8 cap)
-{
-	u8 cap_id, next_cap_ptr;
-	u16 reg;
-
-	if (!cap_ptr)
-		return 0;
-
-	reg = dw_pcie_ep_readw_dbi(ep, func_no, cap_ptr);
-	cap_id = (reg & 0x00ff);
-
-	if (cap_id > PCI_CAP_ID_MAX)
-		return 0;
-
-	if (cap_id == cap)
-		return cap_ptr;
-
-	next_cap_ptr = (reg & 0xff00) >> 8;
-	return __dw_pcie_ep_find_next_cap(ep, func_no, next_cap_ptr, cap);
-}
-
 static u8 dw_pcie_ep_find_capability(struct dw_pcie_ep *ep, u8 func_no, u8 cap)
 {
-	u8 next_cap_ptr;
-	u16 reg;
-
-	reg = dw_pcie_ep_readw_dbi(ep, func_no, PCI_CAPABILITY_LIST);
-	next_cap_ptr = (reg & 0x00ff);
-
-	return __dw_pcie_ep_find_next_cap(ep, func_no, next_cap_ptr, cap);
+	return PCI_FIND_NEXT_CAP(dw_pcie_ep_read_cfg, PCI_CAPABILITY_LIST,
+				 cap, ep, func_no);
 }
 
 /**

drivers/pci/controller/dwc/pcie-designware.h

@@ -695,6 +695,27 @@ static inline u8 dw_pcie_ep_readb_dbi(struct dw_pcie_ep *ep, u8 func_no,
 	return dw_pcie_ep_read_dbi(ep, func_no, reg, 0x1);
 }
 
+static inline int dw_pcie_ep_read_cfg_byte(struct dw_pcie_ep *ep, u8 func_no,
+					   int where, u8 *val)
+{
+	*val = dw_pcie_ep_readb_dbi(ep, func_no, where);
+	return PCIBIOS_SUCCESSFUL;
+}
+
+static inline int dw_pcie_ep_read_cfg_word(struct dw_pcie_ep *ep, u8 func_no,
+					   int where, u16 *val)
+{
+	*val = dw_pcie_ep_readw_dbi(ep, func_no, where);
+	return PCIBIOS_SUCCESSFUL;
+}
+
+static inline int dw_pcie_ep_read_cfg_dword(struct dw_pcie_ep *ep, u8 func_no,
+					    int where, u32 *val)
+{
+	*val = dw_pcie_ep_readl_dbi(ep, func_no, where);
+	return PCIBIOS_SUCCESSFUL;
+}
+
 static inline unsigned int dw_pcie_ep_get_dbi2_offset(struct dw_pcie_ep *ep,
 						      u8 func_no)
 {