linux-kernel - [PATCH 3/4] phy: fsl-imx8mq-usb: support alternate reference clock

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Message-Id: <20250919-usb-phy-alt-clk-support-v1-3-57c2a13eea1c@nxp.com>
Date: Fri, 19 Sep 2025 15:02:59 +0800
From: Xu Yang <xu.yang_2@....com>
To: Vinod Koul <vkoul@...nel.org>, 
 Kishon Vijay Abraham I <kishon@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Li Jun <jun.li@....com>, 
 Abel Vesa <abelvesa@...nel.org>, Peng Fan <peng.fan@....com>, 
 Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>
Cc: linux-phy@...ts.infradead.org, devicetree@...r.kernel.org, 
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org, 
 Xu Yang <xu.yang_2@....com>
Subject: [PATCH 3/4] phy: fsl-imx8mq-usb: support alternate reference clock

This phy supports both 24MHz and 100MHz clock inputs. By default it's
using XTAL 24MHz and the 100MHz clock is a alternate reference clock.
Add supports to use alternate reference clock in case 24MHz clock
can't work well.

Signed-off-by: Xu Yang <xu.yang_2@....com>
---
 drivers/phy/freescale/phy-fsl-imx8mq-usb.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
index b94f242420fc733cd75abef8ba1cd4f59ac18eb5..ad8a55012e42f2c15496955d00c6d5fd85c5beb2 100644
--- a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
+++ b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
@@ -16,6 +16,7 @@
 #define PHY_CTRL0_REF_SSP_EN		BIT(2)
 #define PHY_CTRL0_FSEL_MASK		GENMASK(10, 5)
 #define PHY_CTRL0_FSEL_24M		0x2a
+#define PHY_CTRL0_FSEL_100M		0x27
 
 #define PHY_CTRL1			0x4
 #define PHY_CTRL1_RESET			BIT(0)
@@ -108,6 +109,7 @@ struct tca_blk {
 struct imx8mq_usb_phy {
 	struct phy *phy;
 	struct clk *clk;
+	struct clk *alt_clk;
 	void __iomem *base;
 	struct regulator *vbus;
 	struct tca_blk *tca;
@@ -582,7 +584,8 @@ static int imx8mp_usb_phy_init(struct phy *phy)
 	/* USB3.0 PHY signal fsel for 24M ref */
 	value = readl(imx_phy->base + PHY_CTRL0);
 	value &= ~PHY_CTRL0_FSEL_MASK;
-	value |= FIELD_PREP(PHY_CTRL0_FSEL_MASK, PHY_CTRL0_FSEL_24M);
+	value |= FIELD_PREP(PHY_CTRL0_FSEL_MASK, imx_phy->alt_clk ?
+			    PHY_CTRL0_FSEL_100M : PHY_CTRL0_FSEL_24M);
 	writel(value, imx_phy->base + PHY_CTRL0);
 
 	/* Disable alt_clk_en and use internal MPLL clocks */
@@ -626,13 +629,24 @@ static int imx8mq_phy_power_on(struct phy *phy)
 	if (ret)
 		return ret;
 
-	return clk_prepare_enable(imx_phy->clk);
+	ret = clk_prepare_enable(imx_phy->clk);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare_enable(imx_phy->alt_clk);
+	if (ret) {
+		clk_disable_unprepare(imx_phy->clk);
+		return ret;
+	}
+
+	return ret;
 }
 
 static int imx8mq_phy_power_off(struct phy *phy)
 {
 	struct imx8mq_usb_phy *imx_phy = phy_get_drvdata(phy);
 
+	clk_disable_unprepare(imx_phy->alt_clk);
 	clk_disable_unprepare(imx_phy->clk);
 	regulator_disable(imx_phy->vbus);
 
@@ -681,6 +695,11 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
 		return PTR_ERR(imx_phy->clk);
 	}
 
+	imx_phy->alt_clk = devm_clk_get_optional(dev, "alt");
+	if (IS_ERR(imx_phy->alt_clk))
+		return dev_err_probe(dev, PTR_ERR(imx_phy->alt_clk),
+				    "Failed to get alt clk\n");
+
 	imx_phy->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(imx_phy->base))
 		return PTR_ERR(imx_phy->base);

-- 
2.34.1