Re: [PATCH v4 3/5] phy: fsl-imx8mq-usb: add runtime PM support

[Xu Yang]

On Fri, Jun 05, 2026 at 11:14:59AM -0400, Frank Li wrote:
> On Fri, Jun 05, 2026 at 07:13:04PM +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 v4:
> >  - replace guard() with PM_RUNTIME_ACQUIRE()
> > Changes in v3:
> >  - new patch
> > ---
> >  drivers/phy/freescale/phy-fsl-imx8mq-usb.c | 62 +++++++++++++++++++++---------
> >  1 file changed, 43 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
> > index 591ddf346061..27aa696f5dd4 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");
> 
> when driver remove, devm will disable clock, which may cause refcound
> wrong if device already suspend by runtime pm

Right, so it's improper to use both devm for clk and runtime PM. I will
remove devm_pm_runtime_set_active_enabled() and use non-devm callbacks
to avoid such issue.

> 
> >  	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 +696,10 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
> >  	if (IS_ERR(imx_phy->base))
> >  		return PTR_ERR(imx_phy->base);
> >
> > +	ret = devm_pm_runtime_set_active_enabled(dev);
> > +	if (ret)
> > +		return dev_err_probe(dev, ret, "Failed to enable runtime PM\n");
> > +
> 
> You have not set auto suspend, so runtime_suspend will never entry.

At the end of __driver_probe_device(), it will call pm_request_idle() for
the device. So runtime_suspend() will run. And the test result align with
this logic.

Thanks,
Xu Yang