On Mon, Jun 03, 2019 at 12:10:28PM +0200, Rafael J. Wysocki wrote:
> On Friday, May 31, 2019 11:16:48 PM CEST Bjorn Helgaas wrote:
> > On Fri, May 31, 2019 at 11:49:30AM +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > >
> > > The current code resumes devices in D3hot during system suspend if
> > > the target power state for them is D3cold, but that is not necessary
> > > in general. It only is necessary to do that if the platform firmware
> > > requires the device to be resumed, but that should be covered by
> > > the platform_pci_need_resume() check anyway, so rework
> > > pci_dev_keep_suspended() to avoid returning 'false' for devices
> > > in D3hot which need not be resumed due to platform firmware
> > > requirements.
> > >
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > > ---
> > > drivers/pci/pci.c | 15 ++++++++++++---
> > > 1 file changed, 12 insertions(+), 3 deletions(-)
> > >
> > > Index: linux-pm/drivers/pci/pci.c
> > > ===================================================================
> > > --- linux-pm.orig/drivers/pci/pci.c
> > > +++ linux-pm/drivers/pci/pci.c
> > > @@ -2474,10 +2474,19 @@ bool pci_dev_keep_suspended(struct pci_d
> > > {
> > > struct device *dev = &pci_dev->dev;
> > > bool wakeup = device_may_wakeup(dev);
> > > + pci_power_t target_state;
> > >
> > > - if (!pm_runtime_suspended(dev)
> > > - || pci_target_state(pci_dev, wakeup) != pci_dev->current_state
> > > - || platform_pci_need_resume(pci_dev))
> > > + if (!pm_runtime_suspended(dev) || platform_pci_need_resume(pci_dev))
> > > + return false;
> > > +
> > > + target_state = pci_target_state(pci_dev, wakeup);
> >
> > Nit, add a blank line here.
>
> OK
>
> > > + /*
> > > + * If the earlier platform check has not triggered, D3cold is just power
> > > + * removal on top of D3hot, so no need to resume the device in that
> > > + * case.
> > > + */
> > > + if (target_state != pci_dev->current_state &&
> > > + target_state != PCI_D3cold && pci_dev->current_state != PCI_D3hot)
> > > return false;
> >
> > This is more a comment on the existing code than on this particular
> > patch, but I find this whole function hard to understand, and I think
> > one reason is that there are a lot of negative conditions, both in
> > this function and in its callers. This "target_state != ... &&
> > target_state != ... && current_state != ..." is one example. Another
> > is the function name itself. It might be easier to read as something
> > like this:
> >
> > bool pci_dev_need_resume(...)
> > {
> > if (!pm_runtime_suspended(...))
> > return true;
> >
> > if (platform_pci_need_resume(...))
> > return true;
> >
> > if (target_state != current_state)
> > return true;
>
> Please see the appended (untested) patch on top of the $subject one.
I like it a lot, thanks! I think it makes it a lot more readable.
> > Another reason I think it's hard to read is that
> > "pci_dev_keep_suspended" suggests that this is a pure boolean function
> > without side-effects, but in fact it also fiddles with the PME state
> > in some cases. I don't have any ideas for that part.
>
> Well, I can only propose to put the PME adjustment part into a separate function like
> in the patch below.
>
> ---
> drivers/pci/pci-driver.c | 21 ++++++++++++++++---
> drivers/pci/pci.c | 50 ++++++++++++++++++++++++-----------------------
> drivers/pci/pci.h | 3 +-
> 3 files changed, 46 insertions(+), 28 deletions(-)
>
> Index: linux-pm/drivers/pci/pci.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.c
> +++ linux-pm/drivers/pci/pci.c
> @@ -2459,54 +2459,56 @@ bool pci_dev_run_wake(struct pci_dev *de
> EXPORT_SYMBOL_GPL(pci_dev_run_wake);
>
> /**
> - * pci_dev_keep_suspended - Check if the device can stay in the suspended state.
> + * pci_dev_need_resume - Check if the device can stay in the suspended state.
> * @pci_dev: Device to check.
> *
> - * Return 'true' if the device is runtime-suspended, it doesn't have to be
> + * Return 'false' if the device is runtime-suspended, it doesn't have to be
> * reconfigured due to wakeup settings difference between system and runtime
> * suspend and the current power state of it is suitable for the upcoming
> * (system) transition.
> - *
> - * If the device is not configured for system wakeup, disable PME for it before
> - * returning 'true' to prevent it from waking up the system unnecessarily.
> */
> -bool pci_dev_keep_suspended(struct pci_dev *pci_dev)
> +bool pci_dev_need_resume(struct pci_dev *pci_dev)
> {
> struct device *dev = &pci_dev->dev;
> - bool wakeup = device_may_wakeup(dev);
> pci_power_t target_state;
>
> if (!pm_runtime_suspended(dev) || platform_pci_need_resume(pci_dev))
> - return false;
> + return true;
>
> - target_state = pci_target_state(pci_dev, wakeup);
> + target_state = pci_target_state(pci_dev, device_may_wakeup(dev));
> /*
> * If the earlier platform check has not triggered, D3cold is just power
> * removal on top of D3hot, so no need to resume the device in that
> * case.
> */
> - if (target_state != pci_dev->current_state &&
> - target_state != PCI_D3cold && pci_dev->current_state != PCI_D3hot)
> - return false;
> + return target_state != pci_dev->current_state &&
> + target_state != PCI_D3cold &&
> + pci_dev->current_state != PCI_D3hot;
> +}
> +
> +/**
> + * pci_dev_adjust_pme - Adjust PME setting for a suspended device.
> + * @pci_dev: Device to check.
> + *
> + * If the device is not configured for system wakeup, disable PME for it to
> + * prevent it from waking up the system unnecessarily.
> + */
> +void pci_dev_adjust_pme(struct pci_dev *pci_dev)
> +{
> + struct device *dev = &pci_dev->dev;
>
> - /*
> - * At this point the device is good to go unless it's been configured
> - * to generate PME at the runtime suspend time, but it is not supposed
> - * to wake up the system. In that case, simply disable PME for it
> - * (it will have to be re-enabled on exit from system resume).
> - *
> - * If the device's power state is D3cold and the platform check above
> - * hasn't triggered, the device's configuration is suitable and we don't
> - * need to manipulate it at all.
> - */
> spin_lock_irq(&dev->power.lock);
>
> + /*
> + * If the device's power state is D3cold and the platform check in
> + * pci_dev_need_resume() hasn't triggered, the device's configuration is
> + * suitable and it need not be touched.
I guess "it need not be touched" == "we don't need to disable PME"?
> + */
> if (pm_runtime_suspended(dev) && pci_dev->current_state < PCI_D3cold &&
> - !wakeup)
> + !device_may_wakeup(dev))
> __pci_pme_active(pci_dev, false);
>
> spin_unlock_irq(&dev->power.lock);
> - return true;
> }
>
> /**
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -679,6 +679,7 @@ static bool pci_has_legacy_pm_support(st
> static int pci_pm_prepare(struct device *dev)
> {
> struct device_driver *drv = dev->driver;
> + struct pci_dev *pci_dev = to_pci_dev(dev);
>
> if (drv && drv->pm && drv->pm->prepare) {
> int error = drv->pm->prepare(dev);
> @@ -688,7 +689,15 @@ static int pci_pm_prepare(struct device
> if (!error && dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_PREPARE))
> return 0;
> }
> - return pci_dev_keep_suspended(to_pci_dev(dev));
> + if (pci_dev_need_resume(pci_dev))
> + return 0;
> +
> + /*
> + * The PME setting needs to be adjusted here in case the direct-complete
> + * optimization is used with respect to this device.
> + */
> + pci_dev_adjust_pme(pci_dev);
> + return 1;
> }
>
> static void pci_pm_complete(struct device *dev)
> @@ -758,9 +767,11 @@ static int pci_pm_suspend(struct device
> * better to resume the device from runtime suspend here.
> */
> if (!dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND) ||
> - !pci_dev_keep_suspended(pci_dev)) {
> + pci_dev_need_resume(pci_dev)) {
> pm_runtime_resume(dev);
> pci_dev->state_saved = false;
> + } else {
> + pci_dev_adjust_pme(pci_dev);
> }
>
> if (pm->suspend) {
> @@ -1108,8 +1119,12 @@ static int pci_pm_poweroff(struct device
>
> /* The reason to do that is the same as in pci_pm_suspend(). */
> if (!dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND) ||
> - !pci_dev_keep_suspended(pci_dev))
> + pci_dev_need_resume(pci_dev)) {
> pm_runtime_resume(dev);
> + pci_dev->state_saved = false;
> + } else {
> + pci_dev_adjust_pme(pci_dev);
> + }
>
> pci_dev->state_saved = false;
> if (pm->poweroff) {
> Index: linux-pm/drivers/pci/pci.h
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.h
> +++ linux-pm/drivers/pci/pci.h
> @@ -82,7 +82,8 @@ int pci_finish_runtime_suspend(struct pc
> void pcie_clear_root_pme_status(struct pci_dev *dev);
> int __pci_pme_wakeup(struct pci_dev *dev, void *ign);
> void pci_pme_restore(struct pci_dev *dev);
> -bool pci_dev_keep_suspended(struct pci_dev *dev);
> +bool pci_dev_need_resume(struct pci_dev *dev);
> +void pci_dev_adjust_pme(struct pci_dev *dev);
> void pci_dev_complete_resume(struct pci_dev *pci_dev);
> void pci_config_pm_runtime_get(struct pci_dev *dev);
> void pci_config_pm_runtime_put(struct pci_dev *dev);
>
>
>
