Re: [PATCH v6 3/6] phy: fsl-imx8mq-usb: add runtime PM support

[Frank Li]

On Thu, Jul 16, 2026 at 07:32:59PM +0800, Xu Yang wrote:
> On Wed, Jul 15, 2026 at 10:28:05AM -0500, Frank Li wrote:
> > On Wed, Jul 15, 2026 at 07:33:58PM +0800, Xu Yang wrote:
> > > From: Xu Yang <xu.yang_2@xxxxxxx>
> > >
> > > 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@xxxxxxx>
> > >
> > > ---
> > > Changes in v6:
> > >  - use devm_pm_runtime_enable() to disable runtime PM when probe fails
> > >  - simply pm_runtime_get_sync/disable/put_noidle() to pm_runtime_resume()
> > > 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 | 67 +++++++++++++++++++++---------
> > >  1 file changed, 48 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..bc804d2b5aee 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;
> > > @@ -686,6 +673,7 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
> > >  	struct device *dev = &pdev->dev;
> > >  	struct imx8mq_usb_phy *imx_phy;
> > >  	const struct phy_ops *phy_ops;
> > > +	int ret;
> > >
> > >  	imx_phy = devm_kzalloc(dev, sizeof(*imx_phy), GFP_KERNEL);
> > >  	if (!imx_phy)
> > > @@ -693,13 +681,13 @@ 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 +696,11 @@ 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);
> > > +	ret = devm_pm_runtime_enable(dev);
> > > +	if (ret)
> > > +		return dev_err_probe(dev, ret, "failed to enable runtime PM\n");
> > > +
> >
> > no place to call pm runtime suspend, so whole driver's life cycle runtime
> > pm is on, is it expected?
>
> First, at the end of __driver_probe_device(), it will call pm_request_idle()
> for the device. So runtime_suspend() will run.
> Second, this platform device is the parent of created phy device, the runtime status
> of phy device is managed by phy core, so this platform device will be managed by phy
> core indirectly.
>
> Just found it's not suitable to call devm_pm_runtime_enable() here. Because
>
> pm_runtime_disable_action()
>   pm_runtime_dont_use_autosuspend()
>     update_autosuspend()
>       rpm_idle()
>
> then after remove(), runtime suspend func will still be called. Clocks may be
> disabled twice. I will use non-devm version pm_runtime_enable() in next version.

This should be common problem. Your case should be typical one.
try devm_pm_runtime_set_active_enabled().

Frank

>
> Thanks,
> Xu Yang