linux-kernel - [PATCH 01/13] PCI: dwc: Add dw_pcie_clear_and_set

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Message-Id: <20250611163057.860353-1-18255117159@163.com>
Date: Thu, 12 Jun 2025 00:30:57 +0800
From: Hans Zhang <18255117159@....com>
To: lpieralisi@...nel.org,
	bhelgaas@...gle.com,
	mani@...nel.org,
	kwilczynski@...nel.org
Cc: robh@...nel.org,
	jingoohan1@...il.com,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Hans Zhang <18255117159@....com>
Subject: [PATCH 01/13] PCI: dwc: Add dw_pcie_clear_and_set_dword() for register bit manipulation

DesignWare PCIe controller drivers implement register bit manipulation
through explicit read-modify-write sequences. These patterns appear
repeatedly across multiple drivers with minor variations, creating
code duplication and maintenance overhead.

Implement dw_pcie_clear_and_set_dword() helper to encapsulate atomic
register modification. The function reads the current register value,
clears specified bits, sets new bits, and writes back the result in
a single operation. This abstraction hides bitwise manipulation details
while ensuring consistent behavior across all usage sites.

Centralizing this logic reduces future maintenance effort when modifying
register access patterns and minimizes the risk of implementation
divergence between drivers.

Signed-off-by: Hans Zhang <18255117159@....com>
---
 drivers/pci/controller/dwc/pcie-designware.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index ce9e18554e42..f401c144df0f 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -707,6 +707,17 @@ static inline void dw_pcie_ep_writel_dbi2(struct dw_pcie_ep *ep, u8 func_no,
 	dw_pcie_ep_write_dbi2(ep, func_no, reg, 0x4, val);
 }

+static inline void dw_pcie_clear_and_set_dword(struct dw_pcie *pci, int pos,
+					       u32 clear, u32 set)
+{
+	u32 val;
+
+	val = dw_pcie_readl_dbi(pci, pos);
+	val &= ~clear;
+	val |= set;
+	dw_pcie_writel_dbi(pci, pos, val);
+}
+
 static inline void dw_pcie_dbi_ro_wr_en(struct dw_pcie *pci)
 {
 	u32 reg;
-- 
2.25.1