linux-kernel - [v6 2/5] PCI: dwc: Use common PCI host bridge APIs for finding the capabilities

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Message-Id: <20250323164852.430546-3-18255117159@163.com>
Date: Mon, 24 Mar 2025 00:48:49 +0800
From: Hans Zhang <18255117159@....com>
To: lpieralisi@...nel.org
Cc: kw@...ux.com,
	manivannan.sadhasivam@...aro.org,
	robh@...nel.org,
	bhelgaas@...gle.com,
	jingoohan1@...il.com,
	thomas.richard@...tlin.com,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Hans Zhang <18255117159@....com>
Subject: [v6 2/5] PCI: dwc: Use common PCI host bridge APIs for finding the capabilities

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

Signed-off-by: Hans Zhang <18255117159@....com>
---
Changes since v5:
https://lore.kernel.org/linux-pci/20250321163803.391056-3-18255117159@163.com/

- Kconfig add "select PCI_HOST_HELPERS"
---
 drivers/pci/controller/dwc/Kconfig           |  1 +
 drivers/pci/controller/dwc/pcie-designware.c | 71 ++------------------
 2 files changed, 6 insertions(+), 66 deletions(-)

diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
index b6d6778b0698..c71b3ad44f3e 100644
--- a/drivers/pci/controller/dwc/Kconfig
+++ b/drivers/pci/controller/dwc/Kconfig
@@ -5,6 +5,7 @@ menu "DesignWare-based PCIe controllers"
 
 config PCIE_DW
 	bool
+	select PCI_HOST_HELPERS
 
 config PCIE_DW_HOST
 	bool
diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 145e7f579072..0329f233cf11 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -203,83 +203,22 @@ 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 u32 dwc_pcie_read_cfg(void *priv, int where, int size)
 {
-	u8 cap_id, next_cap_ptr;
-	u16 reg;
-
-	if (!cap_ptr)
-		return 0;
-
-	reg = dw_pcie_readw_dbi(pci, cap_ptr);
-	cap_id = (reg & 0x00ff);
-
-	if (cap_id > PCI_CAP_ID_MAX)
-		return 0;
+	struct dw_pcie *pci = priv;
 
-	if (cap_id == cap)
-		return cap_ptr;
-
-	next_cap_ptr = (reg & 0xff00) >> 8;
-	return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
+	return dw_pcie_read_dbi(pci, where, size);
 }
 
 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_host_bridge_find_capability(pci, dwc_pcie_read_cfg, cap);
 }
 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_host_bridge_find_ext_capability(pci, dwc_pcie_read_cfg, cap);
 }
 EXPORT_SYMBOL_GPL(dw_pcie_find_ext_capability);
 
-- 
2.25.1