Put the NIC in runtime suspended during s2ram

The NIC is put in runtime suspend status when there is no cable connected. As a result, it is safe to keep non-wakeup NIC in runtime suspended during s2ram because the system does not rely on the NIC plug event nor WoL to wake up the system. Besides that, unlike the s2idle, s2ram does not need to manipulate S0ix settings during suspend.

This patch introduces the .prepare() for e1000e so that if the NIC is runtime suspended the subsequent suspend/resume hooks will be skipped so as to speed up the s2ram. The pm core will check whether the NIC is a wake up device so there's no need to check it again in .prepare(). DPM_FLAG_SMART_PREPARE flag should be set during probe to ask the pci subsystem to honor the driver's prepare() result. Besides, the NIC remains runtime suspended after resumed from s2ram as there is no need to resume it.

Tested on i7-2600K with 82579V NIC
Before the patch:
e1000e 0000:00:19.0: pci_pm_suspend+0x0/0x160 returned 0 after 225146 usecs e1000e 0000:00:19.0: pci_pm_resume+0x0/0x90 returned 0 after 140588 usecs

After the patch:
echo disabled > //sys/devices/pci0000\:00/0000\:00\:19.0/power/wakeup becomes 0 usecs because the hooks will be skipped.

Suggested-by Kai-Heng Feng <[email protected]>

Signed-off-by Chen Yu <[email protected]>

---
v2: Added test data and some commit log revise(Paul Menzel)
Only skip the suspend/resume if the NIC is not a wake up device specified by the user(Kai-Heng Feng)
v3: Leverage direct complete mechanism to skip all hooks(Kai-Heng Feng)
---
drivers/net/ethernet/intel/e1000e/netdev.c | 10 +++++++++-

1 file changed, 9 insertions(+), 1 deletion(-)

drivers/net/ethernet/intel/e1000e/netdev.c +7 -0

index b30f00891c03..b210bba3f20a 100644
@@ -25,6 +25,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/aer.h>
 #include <linux/prefetch.h>
+#include <linux/suspend.h>
 
 #include "e1000.h"
 

@@ -6957,6 +6958,12 @@ static int __e1000_resume(struct pci_dev *pdev)
 	return 0;
 }
 
+static int e1000e_pm_prepare(struct device *dev)
+{
+	return pm_runtime_suspended(dev) &&
+		pm_suspend_via_firmware();
+}
+
 static __maybe_unused int e1000e_pm_suspend(struct device *dev)
 {
 	struct net_device *netdev = pci_get_drvdata(to_pci_dev(dev));

drivers/net/ethernet/intel/e1000e/netdev.c +0 -0

 	.suspend	= e1000e_pm_suspend,
 	.resume		= e1000e_pm_resume,
 	.freeze		= e1000e_pm_freeze,

Signature · 1 line

2.17.1

Quoted 7 lines

---
v2: Added test data and some commit log revise(Paul Menzel)
Only skip the suspend/resume if the NIC is not a wake up device specified by the user(Kai-Heng Feng)
v3: Leverage direct complete mechanism to skip all hooks(Kai-Heng Feng)
---

drivers/net/ethernet/intel/e1000e/netdev.c static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent) · line 7675

Quoted 2 lines

drivers/net/ethernet/intel/e1000e/netdev.c +1 -1

-	dev_pm_set_driver_flags(&pdev->dev, DPM_FLAG_NO_DIRECT_COMPLETE);
+	dev_pm_set_driver_flags(&pdev->dev, DPM_FLAG_SMART_PREPARE);

This isn't required for pci_pm_prepare() to use driver's .prepare callback.

drivers/net/ethernet/intel/e1000e/netdev.c MODULE_DEVICE_TABLE(pci, e1000_pci_tbl); · line 7900

Quoted 8 lines

	if (pci_dev_run_wake(pdev) && hw->mac.type < e1000_pch_cnp)
		pm_runtime_put_noidle(&pdev->dev);

drivers/net/ethernet/intel/e1000e/netdev.c +1 -0

@@ -7890,6 +7897,7 @@ MODULE_DEVICE_TABLE(pci, e1000_pci_tbl);
 
 static const struct dev_pm_ops e1000_pm_ops = {
 #ifdef CONFIG_PM_SLEEP
+	.prepare	= e1000e_pm_prepare,

How do we make sure a link change happened in S3 can be detect after resume, without a .complete callback which ask device to runtime resume?

Kai-Heng