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Message-ID: <f75d6cd2-fa9f-4820-969f-2a8839d78c9e@rowland.harvard.edu>
Date: Tue, 31 Oct 2023 10:39:19 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Guan-Yu Lin <guanyulin@...gle.com>
Cc: gregkh@...uxfoundation.org, rafael@...nel.org, len.brown@...el.com,
pavel@....cz, heikki.krogerus@...ux.intel.com, mkl@...gutronix.de,
hadess@...ess.net, mailhol.vincent@...adoo.fr,
ivan.orlov0322@...il.com, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
pumahsu@...gle.com, raychi@...gle.com, albertccwang@...gle.com
Subject: Re: [PATCH] rpm: pm: enable PM_RPM_EXCEPTION config flag
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
Your patch affects all forms of system suspend, not just
suspend-to-idle. What do you actually mean here?
> 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.
This sort of arrangement -- a device shared between two different
systems -- could happen with any sort of device. Why does your patch
affect only USB devices?
> 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"
Runtime Power Management is a form of Power Management, so what you
wrote doesn't make sense. What you really meant is: Prioritize Runtime
Power Management more than System Power Management.
> + default n
> + help
> + Provides a way to prioritize Runtime Power Management more than Power
> + Management. This way system can suspnd with maintaining specific
s/suspnd/suspend/
s/with/while/
> + components in operation.
Your patch does not allow _specific_ components to be kept in operation.
_All_ in-use components that support prioritized PM (with this patch,
all USB components) will remain powered during system suspend, even if
the user wants only _some_ of them to be kept powered.
Alan Stern
> +
> config PM_DEBUG
> bool "Power Management Debug Support"
> depends on PM
> --
> 2.42.0.820.g83a721a137-goog
>
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