[PATCH] PCI: endpoint: 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 EP driver.

Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
---
- Submissions based on the following patches:
https://patchwork.kernel.org/project/linux-pci/patch/20250607161405.808585-1-18255117159@xxxxxxx/

Recently, I checked the code and found that there are still some areas that can be further optimized.
The above series of patches has been around for a long time, so I'm sending this one out for review
as a separate patch.
---
 .../pci/controller/dwc/pcie-designware-ep.c   | 39 +++++++------------
 1 file changed, 14 insertions(+), 25 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 0ae54a94809b..9f1880cc1925 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -69,37 +69,26 @@ 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)
+static int dw_pcie_ep_read_cfg(void *priv, u8 func_no, int where, int size, u32 *val)
 {
-	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;
+	struct dw_pcie_ep *ep = priv;
+
+	if (size == 4)
+		*val = dw_pcie_ep_readl_dbi(ep, func_no, where);
+	else if (size == 2)
+		*val = dw_pcie_ep_readw_dbi(ep, func_no, where);
+	else if (size == 1)
+		*val = dw_pcie_ep_readb_dbi(ep, func_no, where);
+	else
+		return PCIBIOS_BAD_REGISTER_NUMBER;
 
-	next_cap_ptr = (reg & 0xff00) >> 8;
-	return __dw_pcie_ep_find_next_cap(ep, func_no, next_cap_ptr, cap);
+	return PCIBIOS_SUCCESSFUL;
 }
 
 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_TTL(dw_pcie_ep_read_cfg, PCI_CAPABILITY_LIST,
+				     cap, ep, func_no);
 }
 
 /**

base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
-- 
2.25.1