[PATCH v2 3/4] phy: fsl-imx8mq-usb: support alternate reference clock

Xu Yang
2025-10-10T11:01:22Z

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.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

---
Changes in v2:
- add Rb tag
---
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