linux-kernel - [PATCH v6 3/3] PCI: imx6: Add external reference clock mode support

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Message-Id: <20250917045238.1048484-4-hongxing.zhu@nxp.com>
Date: Wed, 17 Sep 2025 12:52:38 +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,
	krzk+dt@...nel.org,
	conor+dt@...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,
	devicetree@...r.kernel.org,
	imx@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Richard Zhu <hongxing.zhu@....com>,
	Frank Li <Frank.Li@....com>
Subject: [PATCH v6 3/3] PCI: imx6: Add external reference clock mode support

i.MX95 PCIes have two reference clock inputs: one from internal PLL,
the other from off chip crystal oscillator. Use extref clock name to be
onhalf of the reference clock comes from external crystal oscillator.

Add external reference clock mode support when extref clock is present.

Signed-off-by: Richard Zhu <hongxing.zhu@....com>
Reviewed-by: Frank Li <Frank.Li@....com>
---
 drivers/pci/controller/dwc/pci-imx6.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 80e48746bbaf..e2ca8b036253 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;
@@ -241,6 +242,8 @@ static unsigned int imx_pcie_grp_offset(const struct imx_pcie *imx_pcie)
 
 static int imx95_pcie_init_phy(struct imx_pcie *imx_pcie)
 {
+	bool ext = imx_pcie->enable_ext_refclk;
+
 	/*
 	 * ERR051624: The Controller Without Vaux Cannot Exit L23 Ready
 	 * Through Beacon or PERST# De-assertion
@@ -259,13 +262,12 @@ 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,
+	regmap_update_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_PHY_GEN_CTRL,
+			   ext ? IMX95_PCIE_REF_USE_PAD : 0,
+			   IMX95_PCIE_REF_USE_PAD);
+	regmap_update_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_SS_RW_REG_0,
 			   IMX95_PCIE_REF_CLKEN,
-			   IMX95_PCIE_REF_CLKEN);
+			   ext ? 0 : IMX95_PCIE_REF_CLKEN);
 
 	return 0;
 }
@@ -1606,7 +1608,7 @@ 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);
@@ -1657,6 +1659,10 @@ 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");
+	imx_pcie->enable_ext_refclk = false;
+	for (i = 0; i < imx_pcie->num_clks; i++)
+		if (strncmp(imx_pcie->clks[i].id, "extref", 6) == 0)
+			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