[v4 3/4] PCI: cadence: Add configuration space capability search API

[Hans Zhang]

Add configuration space capability search API using struct cdns_pcie*
pointer.

Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
---
Changes since v2~v3:
https://lore.kernel.org/linux-pci/20250308133903.322216-1-18255117159@xxxxxxx/
https://lore.kernel.org/linux-pci/20250321040358.360755-4-18255117159@xxxxxxx/

- Introduce generic capability search functions

Changes since v1:
https://lore.kernel.org/linux-pci/20250123070935.1810110-1-18255117159@xxxxxxx

- Added calling the new API in PCI-Cadence ep.c.
- Add a commit message reason for adding the API.
---
 drivers/pci/controller/cadence/pcie-cadence.c | 25 +++++++++++++++++++
 drivers/pci/controller/cadence/pcie-cadence.h |  3 +++
 2 files changed, 28 insertions(+)

diff --git a/drivers/pci/controller/cadence/pcie-cadence.c b/drivers/pci/controller/cadence/pcie-cadence.c
index 204e045aed8c..ea9bfbe76cd6 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.c
+++ b/drivers/pci/controller/cadence/pcie-cadence.c
@@ -8,6 +8,31 @@
 
 #include "pcie-cadence.h"
 
+static u32 cdns_pcie_read_cfg(void *priv, int where, int size)
+{
+	struct cdns_pcie *pcie = priv;
+	u32 val;
+
+	if (size == 4)
+		val = readl(pcie->reg_base + where);
+	else if (size == 2)
+		val = readw(pcie->reg_base + where);
+	else if (size == 1)
+		val = readb(pcie->reg_base + where);
+
+	return val;
+}
+
+u8 cdns_pcie_find_capability(struct cdns_pcie *pcie, u8 cap)
+{
+	return pci_generic_find_capability(pcie, cdns_pcie_read_cfg, cap);
+}
+
+u16 cdns_pcie_find_ext_capability(struct cdns_pcie *pcie, u8 cap)
+{
+	return pci_generic_find_ext_capability(pcie, cdns_pcie_read_cfg, cap);
+}
+
 void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie)
 {
 	u32 delay = 0x3;
diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index f5eeff834ec1..6f4981fccb94 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -557,6 +557,9 @@ static inline int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
 }
 #endif
 
+u8 cdns_pcie_find_capability(struct cdns_pcie *pcie, u8 cap);
+u16 cdns_pcie_find_ext_capability(struct cdns_pcie *pcie, u8 cap);
+
 void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie);
 
 void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 busnr, u8 fn,
-- 
2.25.1