linux-kernel - Re: [PATCH 2/5] e1000e: fix pci device enable counter balance

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Date:	Tue, 29 Jan 2013 10:45:18 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	linux-kernel@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	linux-pci@...r.kernel.org, Bruce Allan <bruce.w.allan@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH 2/5] e1000e: fix pci device enable counter balance

Bjorn Helgaas wrote:
> [+cc Rafael @sisk.pl]
>
> On Mon, Jan 28, 2013 at 4:09 PM, Bjorn Helgaas<bhelgaas@...gle.com>  wrote:
>> [+cc Rafael]
>>
>> On Fri, Jan 18, 2013 at 4:42 AM, Konstantin Khlebnikov
>> <khlebnikov@...nvz.org>  wrote:
>>> __e1000_shutdown() calls pci_disable_device() at the end, thus __e1000_resume()
>>> should call pci_enable_device_mem() to keep enable counter in balance.
>>>
>>> Bug was introduced in commit 23606cf5d1192c2b17912cb2ef6e62f9b11de133
>>> ("e1000e / PCI / PM: Add basic runtime PM support (rev. 4)") in v2.6.35
>>>
>>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>>> Cc: e1000-devel@...ts.sourceforge.net
>>> Cc: Jeff Kirsher<jeffrey.t.kirsher@...el.com>
>>> Cc: Bruce Allan<bruce.w.allan@...el.com>
>>> ---
>>>   drivers/net/ethernet/intel/e1000e/netdev.c |    7 +++++++
>>>   1 file changed, 7 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
>>> index 2853c11..6bce796 100644
>>> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
>>> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
>>> @@ -5598,6 +5598,13 @@ static int __e1000_resume(struct pci_dev *pdev)
>>>          pci_restore_state(pdev);
>>>          pci_save_state(pdev);
>>>
>>> +       err = pci_enable_device_mem(pdev);
>>> +       if (err) {
>>> +               dev_err(&pdev->dev,
>>> +                       "Cannot re-enable PCI device after suspend.\n");
>>> +               return err;
>>> +       }
>>
>> Reviewed-by: Bjorn Helgaas<bhelgaas@...gle.com>
>>
>> Seems right to me, and the other users I looked at (igb, azx,
>> virtio_pci) call pci_disable_device() in .suspend() and call
>> pci_enable_device() in .resume() as you propose to do here.
>>
>> I assume the e1000 folks will handle this patch (and the previous one).
>>
>>> +
>>>          e1000e_set_interrupt_capability(adapter);
>>>          if (netif_running(netdev)) {
>>>                  err = e1000_request_irq(adapter);
>>>
>
> I'm still missing something.  In your original report
> (https://lkml.org/lkml/2013/1/1/25), you noticed that "enable_cnt ==
> 0" immediately after boot, after e1000e had claimed the device:

Yep, it rise counter from 0 to 1, and runtime-suspend immediately
decrease it back to 0.

>
>> Right after boot it looks like this:
>>
>> root@...g:/sys/bus/pci/devices# lspci
>> ...
>> 00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network Connection (rev 04)
>> ...
>> root@...g:/sys/bus/pci/devices# cat 0000\:00\:19.0/enable
>> 0
>> here must be '1', not '0'
>
> But these patches only change the e1000e suspend/resume path.  How
> could they change the enable_cnt before you've even done a suspend?

suspend/resume and runtime_suspend/runtime_resume callbacks calls the one
set of functions: __e1000_shutdown() / __e1000_resume()

Any suspend-resume cycle breaks enable_ent balance.
Thus right after boot and first runtime-suspend device cannot wake up
due to first sort of bugs and after first s2ram suspend-resume cycle
driver breaks it's enable_cnt and device no longer can sleep due to
second sort of bugs.

>
> Bjorn

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