Re: [PATCH v8 3/6] phy: fsl-imx8mq-usb: add runtime PM support

On Fri, Jul 31, 2026 at 09:42:39AM -0500, Frank Li wrote:
> On Fri, Jul 31, 2026 at 04:11:21PM +0800, Xu Yang wrote:
> > From: Xu Yang <[email protected]>
> >
> > Add runtime PM support to ensure the PHY clocks are properly gated
> > when the PHY is not in use, reducing power consumption.
> >
> > Clock management is moved from power_on()/power_off() callbacks into
> > the runtime_resume()/runtime_suspend() callbacks respectively. The PHY
> > subsystem core already holds a runtime PM reference around init() and
> > power_on/off() calls, so no explicit clock handling is needed there.
> >
> > Use devm_clk_get_enabled() and devm_clk_get_optional_enabled() in
> > probe() to keep clocks enabled initially. This ensures the PHY remains
> > functional when CONFIG_PM is disabled, where runtime suspend/resume
> > callbacks are never invoked.
> >
> > In tca_blk_typec_switch_set(), replace the manual clk_prepare_enable()
> > / clk_disable_unprepare() pair with PM_RUNTIME_ACQUIRE_IF_ENABLED() to
> > guard register access against a concurrently suspended PHY.
> >
> > Move devm_regulator_get() before pm_runtime_enable() to avoid having
> > to clean up runtime PM state on regulator acquisition failure.
> >
> > In remove(), call pm_runtime_get_sync() before pm_runtime_disable() to
> > ensure the PHY is resumed and clocks are enabled before the devres
> > teardown disables them.
> >
> > Signed-off-by: Xu Yang <[email protected]>
> >
> > ---
> > Changes in v8:
> >  - fix if condition in imx8mq_usb_phy_remove()
> > Changes in v7:
> >  - replase PM_RUNTIME_ACQUIRE()  with PM_RUNTIME_ACQUIRE_IF_ENABLED()
> >  - use non-devm PM runtime callback because it's hard to avoid double clock
> >    disable issue when probe fails or remove the driver
> >  - improve commit message
> > 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 | 103 +++++++++++++++++++++--------
> >  1 file changed, 74 insertions(+), 29 deletions(-)
> >
> > diff --git a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
> > index 3a5788c609e1..42de2cff4d5f 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_IF_ENABLED(&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");
> > @@ -708,44 +696,101 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
> >  	if (IS_ERR(imx_phy->base))
> >  		return PTR_ERR(imx_phy->base);
> >
> > +	imx_phy->vbus = devm_regulator_get(dev, "vbus");
> > +	if (IS_ERR(imx_phy->vbus))
> > +		return dev_err_probe(dev, PTR_ERR(imx_phy->vbus), "failed to get vbus\n");
> > +
> >  	phy_ops = of_device_get_match_data(dev);
> >  	if (!phy_ops)
> >  		return -EINVAL;
> >
> > -	imx_phy->phy = devm_phy_create(dev, NULL, phy_ops);
> > -	if (IS_ERR(imx_phy->phy))
> > -		return PTR_ERR(imx_phy->phy);
> > +	pm_runtime_set_active(dev);
> > +	pm_runtime_enable(dev);
> 
> does devm_pm_runtime_set_active_enabled() work?

Compared to devm_pm_runtime_enable(), devm_pm_runtime_set_active_enabled() just do
pm_runtime_set_active() before devm_pm_runtime_enable() and pm_runtime_set_suspended()
after pm_runtime_disable(). 

It doesn't change the reality that the device may be runtime suspended before undo
devm_clk_get_enabled(), that is clk_disable_unprepare().

In V4, V3, I used devm_pm_runtime_set_active_enabled(), but it didn't work:
https://patchwork.kernel.org/project/imx/patch/[email protected]/
https://patchwork.kernel.org/project/imx/patch/[email protected]/

Thanks,
Xu Yang