linux-kernel - Re: [PATCH] bus: simple-pm-bus: fix forced runtime PM use

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Message-ID: <f8de9c49-aee2-4ce4-b3cf-ee448f9fc293@nxp.com>
Date: Mon, 17 Feb 2025 11:15:25 +0800
From: Liu Ying <victor.liu@....com>
To: Johan Hovold <johan+linaro@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
 Ulf Hansson <ulf.hansson@...aro.org>,
 Geert Uytterhoeven <geert+renesas@...der.be>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bus: simple-pm-bus: fix forced runtime PM use

On 02/14/2025, Johan Hovold wrote:
> The simple-pm-bus driver only enables runtime PM for some buses
> ('simple-pm-bus') yet has started calling pm_runtime_force_suspend() and
> pm_runtime_force_resume() during system suspend unconditionally.
> 
> This currently works, but that is not obvious and depends on
> implementation details which may change at some point.

Fair enough. It's not a good practice to depend on the PM core behaviour.

Acked-by: Liu Ying <victor.liu@....com>

> 
> Add dedicated system sleep ops and only call pm_runtime_force_suspend()
> and pm_runtime_force_resume() for buses that use runtime PM to avoid any
> future surprises.
> 
> Fixes: c45839309c3d ("drivers: bus: simple-pm-bus: Use clocks")
> Cc: Liu Ying <victor.liu@....com>
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/bus/simple-pm-bus.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
> index 5dea31769f9a..d8e029e7e53f 100644
> --- a/drivers/bus/simple-pm-bus.c
> +++ b/drivers/bus/simple-pm-bus.c
> @@ -109,9 +109,29 @@ static int simple_pm_bus_runtime_resume(struct device *dev)
>  	return 0;
>  }
>  
> +static int simple_pm_bus_suspend(struct device *dev)
> +{
> +	struct simple_pm_bus *bus = dev_get_drvdata(dev);
> +
> +	if (!bus)
> +		return 0;
> +
> +	return pm_runtime_force_suspend(dev);
> +}
> +
> +static int simple_pm_bus_resume(struct device *dev)
> +{
> +	struct simple_pm_bus *bus = dev_get_drvdata(dev);
> +
> +	if (!bus)
> +		return 0;
> +
> +	return pm_runtime_force_resume(dev);
> +}
> +
>  static const struct dev_pm_ops simple_pm_bus_pm_ops = {
>  	RUNTIME_PM_OPS(simple_pm_bus_runtime_suspend, simple_pm_bus_runtime_resume, NULL)
> -	NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
> +	NOIRQ_SYSTEM_SLEEP_PM_OPS(simple_pm_bus_suspend, simple_pm_bus_resume)
>  };
>  
>  #define ONLY_BUS	((void *) 1) /* Match if the device is only a bus. */

-- 
Regards,
Liu Ying