linux-kernel - Re: [PATCH v2] PCI / PM: Avoid using device_may

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Message-ID: <2254362.EY9ByagAJb@aspire.rjw.lan>
Date:   Fri, 30 Jun 2017 00:37 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     linux-pci@...r.kernel.org, Bjorn Helgaas <helgaas@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        gregkh@...uxfoundation.org, USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v2] PCI / PM: Avoid using device_may_wakeup() for runtime PM

On Friday, June 23, 2017 02:58:11 PM Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> pci_target_state() calls device_may_wakeup() which checks whether
> or not the device may wake up the system from sleep states, but
> pci_target_state() is used for runtime PM too.
> 
> Since runtime PM is expected to always enable remote wakeup if
> possible, modify pci_target_state() to take additional argument
> indicating whether or not it should look for a state from which
> the device can signal wakeup and pass either the return value
> of device_can_wakeup(), or "false" (if the device itself is not
> wakeup-capable) to it from the code related to runtime PM.
> 
> While at it, fix the comment in pci_dev_run_wake() which is not
> about sleep states.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> -> v2:
> 
> Passing "true" as the second argument to pci_target_state() for runtime PM
> might trigger suboptimal state choices to be made, so pass the return value
> of device_can_wakeup() to it instead and pass "false" to it in pci_dev_run_wake(),
> because that assumes device_can_wakeup() to return "false" already.

This was sent a week ago without any response so far.

Any concerns?

> ---
>  drivers/pci/pci.c |   22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
> 
> Index: linux-pm/drivers/pci/pci.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.c
> +++ linux-pm/drivers/pci/pci.c
> @@ -1982,12 +1982,13 @@ EXPORT_SYMBOL(pci_wake_from_d3);
>  /**
>   * pci_target_state - find an appropriate low power state for a given PCI dev
>   * @dev: PCI device
> + * @wakeup: Whether or not wakeup functionality will be enabled for the device.
>   *
>   * Use underlying platform code to find a supported low power state for @dev.
>   * If the platform can't manage @dev, return the deepest state from which it
>   * can generate wake events, based on any available PME info.
>   */
> -static pci_power_t pci_target_state(struct pci_dev *dev)
> +static pci_power_t pci_target_state(struct pci_dev *dev, bool wakeup)
>  {
>  	pci_power_t target_state = PCI_D3hot;
>  
> @@ -2024,7 +2025,7 @@ static pci_power_t pci_target_state(stru
>  	if (dev->current_state == PCI_D3cold)
>  		target_state = PCI_D3cold;
>  
> -	if (device_may_wakeup(&dev->dev)) {
> +	if (wakeup) {
>  		/*
>  		 * Find the deepest state from which the device can generate
>  		 * wake-up events, make it the target state and enable device
> @@ -2050,13 +2051,14 @@ static pci_power_t pci_target_state(stru
>   */
>  int pci_prepare_to_sleep(struct pci_dev *dev)
>  {
> -	pci_power_t target_state = pci_target_state(dev);
> +	bool wakeup = device_may_wakeup(&dev->dev);
> +	pci_power_t target_state = pci_target_state(dev, wakeup);
>  	int error;
>  
>  	if (target_state == PCI_POWER_ERROR)
>  		return -EIO;
>  
> -	pci_enable_wake(dev, target_state, device_may_wakeup(&dev->dev));
> +	pci_enable_wake(dev, target_state, wakeup);
>  
>  	error = pci_set_power_state(dev, target_state);
>  
> @@ -2089,9 +2091,10 @@ EXPORT_SYMBOL(pci_back_from_sleep);
>   */
>  int pci_finish_runtime_suspend(struct pci_dev *dev)
>  {
> -	pci_power_t target_state = pci_target_state(dev);
> +	pci_power_t target_state;
>  	int error;
>  
> +	target_state = pci_target_state(dev, device_can_wakeup(&dev->dev));
>  	if (target_state == PCI_POWER_ERROR)
>  		return -EIO;
>  
> @@ -2127,8 +2130,8 @@ bool pci_dev_run_wake(struct pci_dev *de
>  	if (!dev->pme_support)
>  		return false;
>  
> -	/* PME-capable in principle, but not from the intended sleep state */
> -	if (!pci_pme_capable(dev, pci_target_state(dev)))
> +	/* PME-capable in principle, but not from the target power state */
> +	if (!pci_pme_capable(dev, pci_target_state(dev, false)))
>  		return false;
>  
>  	while (bus->parent) {
> @@ -2163,9 +2166,10 @@ EXPORT_SYMBOL_GPL(pci_dev_run_wake);
>  bool pci_dev_keep_suspended(struct pci_dev *pci_dev)
>  {
>  	struct device *dev = &pci_dev->dev;
> +	bool wakeup = device_may_wakeup(dev);
>  
>  	if (!pm_runtime_suspended(dev)
> -	    || pci_target_state(pci_dev) != pci_dev->current_state
> +	    || pci_target_state(pci_dev, wakeup) != pci_dev->current_state
>  	    || platform_pci_need_resume(pci_dev)
>  	    || (pci_dev->dev_flags & PCI_DEV_FLAGS_NEEDS_RESUME))
>  		return false;
> @@ -2183,7 +2187,7 @@ bool pci_dev_keep_suspended(struct pci_d
>  	spin_lock_irq(&dev->power.lock);
>  
>  	if (pm_runtime_suspended(dev) && pci_dev->current_state < PCI_D3cold &&
> -	    !device_may_wakeup(dev))
> +	    !wakeup)
>  		__pci_pme_active(pci_dev, false);
>  
>  	spin_unlock_irq(&dev->power.lock);
>