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SubjectRe: [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@intel.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@intel.com>
> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Acked-by: Bjorn Helgaas <bhelgaas@google.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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