linux-kernel - Re: [PATCH] e1000e: Assign DPM_FLAG_SMART_SUSPEND and DPM_FLAG_MAY_SKIP

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Date:   Wed, 25 Nov 2020 01:17:28 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        "moderated list:INTEL ETHERNET DRIVERS" 
        <intel-wired-lan@...ts.osuosl.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Sasha Neftin <sasha.neftin@...el.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: [PATCH] e1000e: Assign DPM_FLAG_SMART_SUSPEND and
 DPM_FLAG_MAY_SKIP_RESUME to speed up s2ram

Hi Yu,

> On Nov 24, 2020, at 23:32, Chen Yu <yu.c.chen@...el.com> wrote:
> 
> The NIC is put in runtime suspend status when there is no wire connected.
> As a result, it is safe to keep this NIC in runtime suspended during s2ram
> because the system does not rely on the NIC plug event nor WOL to wake up
> the system. Unlike the s2idle, s2ram does not need to manipulate S0ix settings
> during suspend.

Please see below for the reason why I explicitly disable direct-complete in the driver.

> 
> This patch assigns DPM_FLAG_SMART_SUSPEND and DPM_FLAG_MAY_SKIP_RESUME
> to the e1000e driver so that the s2ram could skip the .suspend_late(),
> .suspend_noirq() and .resume_noirq() .resume_early() when possible.
> Also skip .suspend() and .resume() if dev_pm_skip_suspend() and
> dev_pm_skip_resume() return true, so as to speed up the s2ram.

If we really want direct-complete here, maybe always set current WoL setting in runtime suspend routine?

> 
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
> drivers/base/power/main.c                  |  2 ++
> drivers/net/ethernet/intel/e1000e/netdev.c | 14 +++++++++++++-
> 2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index c7ac49042cee..9cd8abba8612 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -580,6 +580,7 @@ bool dev_pm_skip_resume(struct device *dev)
> 
> 	return !dev->power.must_resume;
> }
> +EXPORT_SYMBOL_GPL(dev_pm_skip_resume);

I don't think it's a good idea to use this predicate out side of PM core, must_resume may change during suspend process.

> 
> /**
>  * device_resume_noirq - Execute a "noirq resume" callback for given device.
> @@ -2010,3 +2011,4 @@ bool dev_pm_skip_suspend(struct device *dev)
> 	return dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND) &&
> 		pm_runtime_status_suspended(dev);
> }
> +EXPORT_SYMBOL_GPL(dev_pm_skip_suspend);
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index b30f00891c03..d79fddabc553 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -6965,6 +6965,14 @@ static __maybe_unused int e1000e_pm_suspend(struct device *dev)
> 	struct e1000_hw *hw = &adapter->hw;
> 	int rc;
> 
> +	/* Runtime suspended means that there is no wired connection
> +	 * and it has nothing to do with WOL that, we don't need to
> +	 * adjust the WOL settings. So it is safe to put NIC in
> +	 * runtime suspend while doing system suspend.
> +	 */

What about plugging ethernet cable and using WoL after system is suspended?
Commit "e1000e: Exclude device from suspend direct complete optimization" was to address that scenario.

> +	if (dev_pm_skip_suspend(dev))
> +		return 0;
> +
> 	e1000e_flush_lpic(pdev);
> 
> 	e1000e_pm_freeze(dev);
> @@ -6989,6 +6997,9 @@ static __maybe_unused int e1000e_pm_resume(struct device *dev)
> 	struct e1000_hw *hw = &adapter->hw;
> 	int rc;
> 
> +	if (dev_pm_skip_resume(dev))
> +		return 0;
> +
> 	/* Introduce S0ix implementation */
> 	if (hw->mac.type >= e1000_pch_cnp &&
> 	    !e1000e_check_me(hw->adapter->pdev->device))
> @@ -7665,7 +7676,8 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> 
> 	e1000_print_device_info(adapter);
> 
> -	dev_pm_set_driver_flags(&pdev->dev, DPM_FLAG_NO_DIRECT_COMPLETE);
> +	dev_pm_set_driver_flags(&pdev->dev, DPM_FLAG_NO_DIRECT_COMPLETE |
> +				DPM_FLAG_SMART_SUSPEND | DPM_FLAG_MAY_SKIP_RESUME);
> 
> 	if (pci_dev_run_wake(pdev) && hw->mac.type < e1000_pch_cnp)
> 		pm_runtime_put_noidle(&pdev->dev);

Also, most e1000e device on modern platforms doesn't runtime suspend at all after commit "e1000e: Disable runtime PM on CNP+".

Kai-Heng

> -- 
> 2.25.1
>