linux-kernel - Re: [PATCH] PM / sleep: Avoid excess pm_runtime_enable() calls in device

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Date:   Fri, 8 Dec 2017 14:25:56 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH] PM / sleep: Avoid excess pm_runtime_enable() calls in
 device_resume()

On Thu, Dec 07, 2017 at 03:26:14AM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Middle-layer code doing suspend-time optimizations for devices with
> the DPM_FLAG_SMART_SUSPEND flag set (currently, the PCI bus type and
> the ACPI PM domain) needs to make the core skip ->thaw_early and
> ->thaw callbacks for those devices in some cases and it sets the
> power.direct_complete flag for them for this purpose.
> 
> However, it turns out that setting power.direct_complete outside of
> the PM core is a bad idea as it triggers an excessive invocation of
> pm_runtime_enable() in device_resume().
> 
> For this reason, provide a helper to clear power.is_late_suspended
> and power.is_suspended to be invoked by the middle-layer code in
> question instead of setting power.direct_complete and make that code
> call the new helper.
> 
> Fixes: c4b65157aeef (PCI / PM: Take SMART_SUSPEND driver flag into account)
> Fixes: 05087360fd7a (ACPI / PM: Take SMART_SUSPEND driver flag into account)
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

I don't pretend to understand this (and I don't need to, so don't
waste your time explaining), but I trust you :)

> ---
>  drivers/acpi/device_pm.c  |    2 +-
>  drivers/base/power/main.c |   15 +++++++++++++++
>  drivers/pci/pci-driver.c  |    2 +-
>  include/linux/pm.h        |    1 +
>  4 files changed, 18 insertions(+), 2 deletions(-)
> 
> Index: linux-pm/include/linux/pm.h
> ===================================================================
> --- linux-pm.orig/include/linux/pm.h
> +++ linux-pm/include/linux/pm.h
> @@ -765,6 +765,7 @@ extern int pm_generic_poweroff_late(stru
>  extern int pm_generic_poweroff(struct device *dev);
>  extern void pm_generic_complete(struct device *dev);
>  
> +extern void dev_pm_skip_next_resume_phases(struct device *dev);
>  extern bool dev_pm_smart_suspend_and_suspended(struct device *dev);
>  
>  #else /* !CONFIG_PM_SLEEP */
> Index: linux-pm/drivers/base/power/main.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/main.c
> +++ linux-pm/drivers/base/power/main.c
> @@ -526,6 +526,21 @@ static void dpm_watchdog_clear(struct dp
>  /*------------------------- Resume routines -------------------------*/
>  
>  /**
> + * dev_pm_skip_next_resume_phases - Skip next system resume phases for device.
> + * @dev: Target device.
> + *
> + * Make the core skip the "early resume" and "resume" phases for @dev.
> + *
> + * This function can be called by middle-layer code during the "noirq" phase of
> + * system resume if necessary, but not by device drivers.
> + */
> +void dev_pm_skip_next_resume_phases(struct device *dev)
> +{
> +	dev->power.is_late_suspended = false;
> +	dev->power.is_suspended = false;
> +}
> +
> +/**
>   * device_resume_noirq - Execute a "noirq resume" callback for given device.
>   * @dev: Device to handle.
>   * @state: PM transition of the system being carried out.
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -999,7 +999,7 @@ static int pci_pm_thaw_noirq(struct devi
>  	 * the subsequent "thaw" callbacks for the device.
>  	 */
>  	if (dev_pm_smart_suspend_and_suspended(dev)) {
> -		dev->power.direct_complete = true;
> +		dev_pm_skip_next_resume_phases(dev);
>  		return 0;
>  	}
>  
> Index: linux-pm/drivers/acpi/device_pm.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/device_pm.c
> +++ linux-pm/drivers/acpi/device_pm.c
> @@ -1138,7 +1138,7 @@ int acpi_subsys_thaw_noirq(struct device
>  	 * skip all of the subsequent "thaw" callbacks for the device.
>  	 */
>  	if (dev_pm_smart_suspend_and_suspended(dev)) {
> -		dev->power.direct_complete = true;
> +		dev_pm_skip_next_resume_phases(dev);
>  		return 0;
>  	}
>  
> 
> --
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