Re: [PATCH v5 3/5] phy: fsl-imx8mq-usb: add runtime PM support

[Frank Li <Frank.li@oss.nxp.com>]

On Tue, Jun 30, 2026 at 06:11:30PM +0800, Xu Yang wrote:
> From: Xu Yang <xu.yang_2@nxp.com>
>
> Add runtime PM to ensure the PHY is properly powered and clocked during
> register access, preventing potential system hangs.
>
> It guards register access in the following scenarios:
> - PHY operations: init() and power_on/off() callbacks are guarded by
>   phy core
> - Type-C orientation switching when PHY/Controller are suspended which
>   needs explicitly care
> - Future PHY control port register regmap debugfs access
>
> Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
>
> ---
> Changes in v5:
>  - use non-devm PM runtime callback to correctly enable/disable clocks
>    when unbind the device
> Changes in v4:
>  - replace guard() with PM_RUNTIME_ACQUIRE()
> Changes in v3:
>  - new patch
> ---
>  drivers/phy/freescale/phy-fsl-imx8mq-usb.c | 64 +++++++++++++++++++++---------
>  1 file changed, 45 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
> index 3a5788c609e1..9d1dd0e7352e 100644
> --- a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
> +++ b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
> @@ -9,6 +9,7 @@
>  #include <linux/of.h>
>  #include <linux/phy/phy.h>
>  #include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/usb/typec_mux.h>
>
> @@ -136,17 +137,15 @@ static int tca_blk_typec_switch_set(struct typec_switch_dev *sw,
>  {
>  	struct imx8mq_usb_phy *imx_phy = typec_switch_get_drvdata(sw);
>  	struct tca_blk *tca = imx_phy->tca;
> -	int ret;
>
>  	if (tca->orientation == orientation)
>  		return 0;
>
> -	ret = clk_prepare_enable(imx_phy->clk);
> -	if (ret)
> -		return ret;
> +	PM_RUNTIME_ACQUIRE(&imx_phy->phy->dev, pm);
> +	if (PM_RUNTIME_ACQUIRE_ERR(&pm))
> +		return -ENXIO;
>
>  	tca_blk_orientation_set(tca, orientation);
> -	clk_disable_unprepare(imx_phy->clk);
>
>  	return 0;
>  }
> @@ -620,16 +619,6 @@ static int imx8mq_phy_power_on(struct phy *phy)
>  	if (ret)
>  		return ret;
>
> -	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;
> -	}
> -
>  	/* Disable rx term override */
>  	value = readl(imx_phy->base + PHY_CTRL6);
>  	value &= ~PHY_CTRL6_RXTERM_OVERRIDE_SEL;
> @@ -648,8 +637,6 @@ static int imx8mq_phy_power_off(struct phy *phy)
>  	value |= PHY_CTRL6_RXTERM_OVERRIDE_SEL;
>  	writel(value, imx_phy->base + PHY_CTRL6);
>
> -	clk_disable_unprepare(imx_phy->alt_clk);
> -	clk_disable_unprepare(imx_phy->clk);
>  	regulator_disable(imx_phy->vbus);
>
>  	return 0;
> @@ -693,13 +680,13 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
>
>  	platform_set_drvdata(pdev, imx_phy);
>
> -	imx_phy->clk = devm_clk_get(dev, "phy");
> +	imx_phy->clk = devm_clk_get_enabled(dev, "phy");
>  	if (IS_ERR(imx_phy->clk)) {
>  		dev_err(dev, "failed to get imx8mq usb phy clock\n");
>  		return PTR_ERR(imx_phy->clk);
>  	}
>
> -	imx_phy->alt_clk = devm_clk_get_optional(dev, "alt");
> +	imx_phy->alt_clk = devm_clk_get_optional_enabled(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");
> @@ -708,6 +695,9 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
>  	if (IS_ERR(imx_phy->base))
>  		return PTR_ERR(imx_phy->base);
>
> +	pm_runtime_set_active(dev);
> +	pm_runtime_enable(dev);
> +

devm_pm_runtime_enable();

runtime pm will be always on active status, why suspend it?

>  	phy_ops = of_device_get_match_data(dev);
>  	if (!phy_ops)
>  		return -EINVAL;
> @@ -737,15 +727,51 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
>
>  static void imx8mq_usb_phy_remove(struct platform_device *pdev)
>  {
> +	struct device *dev = &pdev->dev;
> +
> +	pm_runtime_get_sync(dev);
> +	pm_runtime_disable(dev);
> +	pm_runtime_put_noidle(dev);
> +}
> +
> +static int imx8mq_usb_phy_runtime_suspend(struct device *dev)
> +{
> +	struct imx8mq_usb_phy *imx_phy = dev_get_drvdata(dev);
> +
> +	clk_disable_unprepare(imx_phy->alt_clk);
> +	clk_disable_unprepare(imx_phy->clk);

can you switch to use bulk clk api.

Frank
> +
> +	return 0;
> +}
> +
> +static int imx8mq_usb_phy_runtime_resume(struct device *dev)
> +{
> +	struct imx8mq_usb_phy *imx_phy = dev_get_drvdata(dev);
> +	int ret;
> +
> +	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 0;
>  }
>
> +static DEFINE_RUNTIME_DEV_PM_OPS(imx8mq_usb_phy_pm_ops, imx8mq_usb_phy_runtime_suspend,
> +				 imx8mq_usb_phy_runtime_resume, NULL);
> +
>  static struct platform_driver imx8mq_usb_phy_driver = {
>  	.probe	= imx8mq_usb_phy_probe,
>  	.remove = imx8mq_usb_phy_remove,
>  	.driver = {
>  		.name	= "imx8mq-usb-phy",
>  		.of_match_table	= imx8mq_usb_phy_of_match,
> +		.pm = pm_ptr(&imx8mq_usb_phy_pm_ops),
>  		.suppress_bind_attrs = true,
>  	}
>  };
>
> --
> 2.34.1
>
>