linux-kernel - [PATCH 04/13] PCI: dwc: Refactor imx6 to use dw_pcie_clear_and_set

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Message-Id: <20250611163121.860619-1-18255117159@163.com>
Date: Thu, 12 Jun 2025 00:31:21 +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 04/13] PCI: dwc: Refactor imx6 to use dw_pcie_clear_and_set_dword()

i.MX6 PCIe driver contains multiple read-modify-write sequences for
link training and speed configuration. These operations manually handle
bit masking and shifting to update specific fields in control registers,
particularly for link capabilities and speed change initiation.

Refactor link capability configuration and speed change handling using
dw_pcie_clear_and_set_dword(). The helper simplifies LNKCAP modification
by encapsulating bit clear/set operations and eliminates intermediate
variables. For speed change control, replace explicit bit manipulation
with direct register updates through the helper.

Adopting the standard interface reduces code complexity in link training
paths and ensures consistent handling of speed-related bits. The change
also prepares the driver for future enhancements to Gen3 link training
by centralizing bit manipulation logic.

Signed-off-by: Hans Zhang <18255117159@....com>
---
 drivers/pci/controller/dwc/pci-imx6.c | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 5a38cfaf989b..3004e432f013 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -941,7 +941,6 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
 	struct imx_pcie *imx_pcie = to_imx_pcie(pci);
 	struct device *dev = pci->dev;
 	u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
-	u32 tmp;
 	int ret;
 
 	if (!(imx_pcie->drvdata->flags &
@@ -956,10 +955,9 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
 	 * bus will not be detected at all.  This happens with PCIe switches.
 	 */
 	dw_pcie_dbi_ro_wr_en(pci);
-	tmp = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
-	tmp &= ~PCI_EXP_LNKCAP_SLS;
-	tmp |= PCI_EXP_LNKCAP_SLS_2_5GB;
-	dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, tmp);
+	dw_pcie_clear_and_set_dword(pci, offset + PCI_EXP_LNKCAP,
+				    PCI_EXP_LNKCAP_SLS,
+				    PCI_EXP_LNKCAP_SLS_2_5GB);
 	dw_pcie_dbi_ro_wr_dis(pci);
 
 	/* Start LTSSM. */
@@ -972,18 +970,16 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
 
 		/* Allow faster modes after the link is up */
 		dw_pcie_dbi_ro_wr_en(pci);
-		tmp = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
-		tmp &= ~PCI_EXP_LNKCAP_SLS;
-		tmp |= pci->max_link_speed;
-		dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, tmp);
+		dw_pcie_clear_and_set_dword(pci, offset + PCI_EXP_LNKCAP,
+					    PCI_EXP_LNKCAP_SLS,
+					    pci->max_link_speed);
 
 		/*
 		 * Start Directed Speed Change so the best possible
 		 * speed both link partners support can be negotiated.
 		 */
-		tmp = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);
-		tmp |= PORT_LOGIC_SPEED_CHANGE;
-		dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, tmp);
+		dw_pcie_clear_and_set_dword(pci, PCIE_LINK_WIDTH_SPEED_CONTROL,
+					    0, PORT_LOGIC_SPEED_CHANGE);
 		dw_pcie_dbi_ro_wr_dis(pci);
 
 		ret = imx_pcie_wait_for_speed_change(imx_pcie);
@@ -1295,7 +1291,6 @@ static void imx_pcie_host_post_init(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct imx_pcie *imx_pcie = to_imx_pcie(pci);
-	u32 val;
 
 	if (imx_pcie->drvdata->flags & IMX_PCIE_FLAG_8GT_ECN_ERR051586) {
 		/*
@@ -1310,9 +1305,8 @@ static void imx_pcie_host_post_init(struct dw_pcie_rp *pp)
 		 * to 0.
 		 */
 		dw_pcie_dbi_ro_wr_en(pci);
-		val = dw_pcie_readl_dbi(pci, GEN3_RELATED_OFF);
-		val &= ~GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL;
-		dw_pcie_writel_dbi(pci, GEN3_RELATED_OFF, val);
+		dw_pcie_clear_and_set_dword(pci, GEN3_RELATED_OFF,
+					    GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL, 0);
 		dw_pcie_dbi_ro_wr_dis(pci);
 	}
 }
-- 
2.25.1