linux-kernel - [PATCH v1 2/2] PCI: imx6: Add external reference clock mode support

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Message-Id: <20250618074848.3898532-2-hongxing.zhu@nxp.com>
Date: Wed, 18 Jun 2025 15:48:48 +0800
From: Richard Zhu <hongxing.zhu@....com>
To: frank.li@....com,
	l.stach@...gutronix.de,
	lpieralisi@...nel.org,
	kwilczynski@...nel.org,
	mani@...nel.org,
	robh@...nel.org,
	bhelgaas@...gle.com,
	shawnguo@...nel.org,
	s.hauer@...gutronix.de,
	kernel@...gutronix.de,
	festevam@...il.com
Cc: linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Richard Zhu <hongxing.zhu@....com>
Subject: [PATCH v1 2/2] PCI: imx6: Add external reference clock mode support

The PCI Express reference clock of i.MX9 PCIes might come from external
clock source. Add the external reference clock mode support.

Signed-off-by: Richard Zhu <hongxing.zhu@....com>
---
 drivers/pci/controller/dwc/pci-imx6.c | 34 ++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 5a38cfaf989b..04c720377546 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -149,6 +149,7 @@ struct imx_pcie {
 	struct gpio_desc	*reset_gpiod;
 	struct clk_bulk_data	*clks;
 	int			num_clks;
+	bool			enable_ext_refclk;
 	struct regmap		*iomuxc_gpr;
 	u16			msi_ctrl;
 	u32			controller_id;
@@ -259,13 +260,24 @@ static int imx95_pcie_init_phy(struct imx_pcie *imx_pcie)
 			IMX95_PCIE_PHY_CR_PARA_SEL,
 			IMX95_PCIE_PHY_CR_PARA_SEL);
 
-	regmap_update_bits(imx_pcie->iomuxc_gpr,
-			   IMX95_PCIE_PHY_GEN_CTRL,
-			   IMX95_PCIE_REF_USE_PAD, 0);
-	regmap_update_bits(imx_pcie->iomuxc_gpr,
-			   IMX95_PCIE_SS_RW_REG_0,
-			   IMX95_PCIE_REF_CLKEN,
-			   IMX95_PCIE_REF_CLKEN);
+	if (imx_pcie->enable_ext_refclk) {
+		/* External clock is used as reference clock */
+		regmap_update_bits(imx_pcie->iomuxc_gpr,
+				   IMX95_PCIE_PHY_GEN_CTRL,
+				   IMX95_PCIE_REF_USE_PAD,
+				   IMX95_PCIE_REF_USE_PAD);
+		regmap_update_bits(imx_pcie->iomuxc_gpr,
+				   IMX95_PCIE_SS_RW_REG_0,
+				   IMX95_PCIE_REF_CLKEN, 0);
+	} else {
+		regmap_update_bits(imx_pcie->iomuxc_gpr,
+				   IMX95_PCIE_PHY_GEN_CTRL,
+				   IMX95_PCIE_REF_USE_PAD, 0);
+		regmap_update_bits(imx_pcie->iomuxc_gpr,
+				   IMX95_PCIE_SS_RW_REG_0,
+				   IMX95_PCIE_REF_CLKEN,
+				   IMX95_PCIE_REF_CLKEN);
+	}
 
 	return 0;
 }
@@ -1600,7 +1612,7 @@ static int imx_pcie_probe(struct platform_device *pdev)
 	struct imx_pcie *imx_pcie;
 	struct device_node *np;
 	struct device_node *node = dev->of_node;
-	int ret, domain;
+	int i, ret, domain;
 	u16 val;
 
 	imx_pcie = devm_kzalloc(dev, sizeof(*imx_pcie), GFP_KERNEL);
@@ -1651,6 +1663,12 @@ static int imx_pcie_probe(struct platform_device *pdev)
 	if (imx_pcie->num_clks < 0)
 		return dev_err_probe(dev, imx_pcie->num_clks,
 				     "failed to get clocks\n");
+	for (i = 0; i < imx_pcie->num_clks; i++) {
+		if (strncmp(imx_pcie->clks[i].id, "ref", 3) == 0)
+			imx_pcie->enable_ext_refclk = false;
+		else
+			imx_pcie->enable_ext_refclk = true;
+	}
 
 	if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_HAS_PHYDRV)) {
 		imx_pcie->phy = devm_phy_get(dev, "pcie-phy");
-- 
2.37.1