[PATCH v2 2/3] PCI: cadence: Add cdns_pcie_get_pcie_cap() helper and cache capability offset

[Hans Zhang]

Add a helper cdns_pcie_get_pcie_cap() that finds and caches the
PCIe Capability offset in struct cdns_pcie::pcie_cap. This avoids
repeated searches and follows the pattern used in other PCIe drivers.

The helper uses cdns_pcie_find_capability() to locate PCI_CAP_ID_EXP
and stores the result for later use.

This is a preparatory step for removing the hardcoded capability
offset from host driver code.

Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
---
 drivers/pci/controller/cadence/pcie-cadence.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index c057f4b393e6..bbd275193bc1 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -219,6 +219,7 @@ struct cdns_plat_pcie_of_data {
  *       wrapper
  * @cdns_pcie_reg_offsets: Register bank offsets for different SoC
  * @debug_dir: debugfs node
+ * @pcie_cap: PCIe capability offset
  */
 struct cdns_pcie {
 	void __iomem		             *reg_base;
@@ -233,6 +234,7 @@ struct cdns_pcie {
 	const  struct cdns_pcie_ops          *ops;
 	const  struct cdns_plat_pcie_of_data *cdns_pcie_reg_offsets;
 	struct dentry			     *debug_dir;
+	u8				     pcie_cap;
 };
 
 /**
@@ -651,6 +653,22 @@ static inline int cdns_pcie_hpa_ep_setup(struct cdns_pcie_ep *ep)
 
 u8   cdns_pcie_find_capability(struct cdns_pcie *pcie, u8 cap);
 u16  cdns_pcie_find_ext_capability(struct cdns_pcie *pcie, u8 cap);
+
+/**
+ * cdns_pcie_get_pcie_cap() - Return cached PCIe Capability offset
+ * @pcie: Cadence PCIe instance
+ *
+ * Finds and caches the offset of PCI_CAP_ID_EXP on first call.
+ * Returns 0 if the capability is not present.
+ */
+static inline u8 cdns_pcie_get_pcie_cap(struct cdns_pcie *pcie)
+{
+	if (!pcie->pcie_cap)
+		pcie->pcie_cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_EXP);
+
+	return pcie->pcie_cap;
+}
+
 bool cdns_pcie_linkup(struct cdns_pcie *pcie);
 
 void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie);
-- 
2.34.1