linux-kernel - Re: [PATCH v2 2/6] PCI / PM: Support for LEAVE

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Date:   Wed, 8 Nov 2017 14:38:33 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Documentation <linux-doc@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kevin Hilman <khilman@...nel.org>
Subject: Re: [PATCH v2 2/6] PCI / PM: Support for LEAVE_SUSPENDED driver flag

On Wed, Nov 08, 2017 at 02:28:18PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Add support for DPM_FLAG_LEAVE_SUSPENDED to the PCI bus type by
> making it (a) set the power.may_skip_resume status bit for devices
> that, from its perspective, may be left in suspend after system
> wakeup from sleep and (b) return early from pci_pm_resume_noirq()
> for devices whose remaining resume callbacks during the transition
> under way are going to be skipped by the PM core.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

> ---
>  Documentation/power/pci.txt |   11 +++++++++++
>  drivers/pci/pci-driver.c    |   19 +++++++++++++++++--
>  2 files changed, 28 insertions(+), 2 deletions(-)
> 
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -699,7 +699,7 @@ static void pci_pm_complete(struct devic
>  	pm_generic_complete(dev);
>  
>  	/* Resume device if platform firmware has put it in reset-power-on */
> -	if (dev->power.direct_complete && pm_resume_via_firmware()) {
> +	if (pm_runtime_suspended(dev) && pm_resume_via_firmware()) {
>  		pci_power_t pre_sleep_state = pci_dev->current_state;
>  
>  		pci_update_current_state(pci_dev, pci_dev->current_state);
> @@ -783,8 +783,10 @@ static int pci_pm_suspend_noirq(struct d
>  	struct pci_dev *pci_dev = to_pci_dev(dev);
>  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>  
> -	if (dev_pm_smart_suspend_and_suspended(dev))
> +	if (dev_pm_smart_suspend_and_suspended(dev)) {
> +		dev->power.may_skip_resume = true;
>  		return 0;
> +	}
>  
>  	if (pci_has_legacy_pm_support(pci_dev))
>  		return pci_legacy_suspend_late(dev, PMSG_SUSPEND);
> @@ -838,6 +840,16 @@ static int pci_pm_suspend_noirq(struct d
>  Fixup:
>  	pci_fixup_device(pci_fixup_suspend_late, pci_dev);
>  
> +	/*
> +	 * If the target system sleep state is suspend-to-idle, it is sufficient
> +	 * to check whether or not the device's wakeup settings are good for
> +	 * runtime PM.  Otherwise, the pm_resume_via_firmware() check will cause
> +	 * pci_pm_complete() to take care of fixing up the device's state
> +	 * anyway, if need be.
> +	 */
> +	dev->power.may_skip_resume = device_may_wakeup(dev) ||
> +					!device_can_wakeup(dev);
> +
>  	return 0;
>  }
>  
> @@ -847,6 +859,9 @@ static int pci_pm_resume_noirq(struct de
>  	struct device_driver *drv = dev->driver;
>  	int error = 0;
>  
> +	if (dev_pm_may_skip_resume(dev))
> +		return 0;
> +
>  	/*
>  	 * Devices with DPM_FLAG_SMART_SUSPEND may be left in runtime suspend
>  	 * during system suspend, so update their runtime PM status to "active"
> Index: linux-pm/Documentation/power/pci.txt
> ===================================================================
> --- linux-pm.orig/Documentation/power/pci.txt
> +++ linux-pm/Documentation/power/pci.txt
> @@ -994,6 +994,17 @@ into D0 going forward), but if it is in
>  the function will set the power.direct_complete flag for it (to make the PM core
>  skip the subsequent "thaw" callbacks for it) and return.
>  
> +Setting the DPM_FLAG_LEAVE_SUSPENDED flag means that the driver prefers the
> +device to be left in suspend after system-wide transitions to the working state.
> +This flag is checked by the PM core, but the PCI bus type informs the PM core
> +which devices may be left in suspend from its perspective (that happens during
> +the "noirq" phase of system-wide suspend and analogous transitions) and next it
> +uses the dev_pm_may_skip_resume() helper to decide whether or not to return from
> +pci_pm_resume_noirq() early, as the PM core will skip the remaining resume
> +callbacks for the device during the transition under way and will set its
> +runtime PM status to "suspended" if dev_pm_may_skip_resume() returns "true" for
> +it.
> +
>  3.2. Device Runtime Power Management
>  ------------------------------------
>  In addition to providing device power management callbacks PCI device drivers
> 
> --
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