On Tue, Oct 31, 2023 at 05:38:55PM +0800, Guan-Yu Lin wrote:
> Introducing PM_RPM_EXCEPTION config flag, which may alter the priority
> between system power management and runtime power management. In
> suspend-to-idle flow, PM core will suspend all devices to avoid device
> interact with the system. However, chances are devices might be used by
> other systems rather than a single system. In this case, PM core shouldn't
> suspend the devices. One may use PM_RPM_EXCEPTION config flag to mark
> such exception, and determine the power state of a device with runtime
> power management rather than system power management.
>
> Signed-off-by: Guan-Yu Lin <guanyulin@xxxxxxxxxx>
> ---
> drivers/usb/core/generic.c | 6 ++++++
> drivers/usb/core/usb.h | 16 ++++++++++++++++
> kernel/power/Kconfig | 8 ++++++++
> 3 files changed, 30 insertions(+)
>
> diff --git a/drivers/usb/core/generic.c b/drivers/usb/core/generic.c
> index 740342a2812a..bb0dfcfc9764 100644
> --- a/drivers/usb/core/generic.c
> +++ b/drivers/usb/core/generic.c
> @@ -266,6 +266,9 @@ int usb_generic_driver_suspend(struct usb_device *udev, pm_message_t msg)
> {
> int rc;
>
> + if (usb_runtime_pm_exception(udev))
> + return 0;
> +
> /* Normal USB devices suspend through their upstream port.
> * Root hubs don't have upstream ports to suspend,
> * so we have to shut down their downstream HC-to-USB
> @@ -294,6 +297,9 @@ int usb_generic_driver_resume(struct usb_device *udev, pm_message_t msg)
> {
> int rc;
>
> + if (usb_runtime_pm_exception(udev))
> + return 0;
> +
> /* Normal USB devices resume/reset through their upstream port.
> * Root hubs don't have upstream ports to resume or reset,
> * so we have to start up their downstream HC-to-USB
> diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
> index 60363153fc3f..14a054f814a2 100644
> --- a/drivers/usb/core/usb.h
> +++ b/drivers/usb/core/usb.h
> @@ -90,6 +90,22 @@ extern void usb_major_cleanup(void);
> extern int usb_device_supports_lpm(struct usb_device *udev);
> extern int usb_port_disable(struct usb_device *udev);
>
> +#ifdef CONFIG_PM_RPM_EXCEPTION
> +
> +static inline int usb_runtime_pm_exception(struct usb_device *udev)
> +{
> + return atomic_read(&udev->dev.power.usage_count);
> +}
> +
> +#else
> +
> +static inline int usb_runtime_pm_exception(struct usb_device *udev)
> +{
> + return 0;
> +}
> +
> +#endif
> +
> #ifdef CONFIG_PM
>
> extern int usb_suspend(struct device *dev, pm_message_t msg);
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 4b31629c5be4..beba7a0f3947 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -193,6 +193,14 @@ config PM
> responsible for the actual handling of device suspend requests and
> wake-up events.
>
> +config PM_RPM_EXCEPTION
> + bool "Prioritize Runtime Power Management more than Power Management"
> + default n
The default is always 'n' so no need to specify it.
> + help
> + Provides a way to prioritize Runtime Power Management more than Power
> + Management. This way system can suspnd with maintaining specific
> + components in operation.
This really doesn't give me a good description of why someone would ever
want to enable this at all.
And why does this have to be a build option? That feels very heavy, why
not make it changable at runtime?
If this is a build option, how are you going to get all the distros and
all of the Android/ChromeOS systems in the world to enable it?
thanks,
greg k-h
