Subject: Re: [PATCH] pci, e1000e: Add and use __pci_disable_link_state

From: Yinghai Lu <[email-masked]>
Date: Thu, 12 May 2011 16:58:57 -0700

On 05/12/2011 04:32 PM, Jesse Barnes wrote:
> On Wed, 11 May 2011 13:23:21 -0700
> Yinghai Lu <[email-masked]> wrote:
> 
>> On 05/09/2011 02:35 PM, Jesse Barnes wrote:
>>> On Sun, 08 May 2011 11:54:32 -0700
>>> Yinghai Lu <[email-masked]> wrote:
>>>
>>>>
>>>> Need to use it in _e1000e_disable_aspm.
>>>> when aer happens,
>>>> pci_walk_bus already have down_read(&pci_bus_sem)...
>>>> then report_slot_reset
>>>>         ==> e1000_io_slot_reset
>>>>                 ==> e1000e_disable_aspm
>>>>                         ==> pci_disable_link_state...
>>>>
>>>> We can not use pci_disable_link_state, and it will try to hold pci_bus_sem again.
>>>>
>>>> Try to have __pci_disable_link_state that will not need to hold pci_bus_sem.
>>>
>>> What about the other callers of e1000e_disable_aspm?  Do they already
>>> have the lock held or is it just reset that needs the already locked
>>> version?
>>
>> yes. 
>>
>> there is another version when aspm is not defined. and it does not use any lock. 
>>
>> #ifdef CONFIG_PCIEASPM
>> static void __e1000e_disable_aspm(struct pci_dev *pdev, u16 state)
>> {
>>         pci_disable_link_state(pdev, state);
>> }
>> #else
>> static void __e1000e_disable_aspm(struct pci_dev *pdev, u16 state)
>> {
>>         int pos;
>>         u16 reg16;
>>
>>         /*
>>          * Both device and parent should have the same ASPM setting.
>>          * Disable ASPM in downstream component first and then upstream.
>>          */
>>         pos = pci_pcie_cap(pdev);
>>         pci_read_config_word(pdev, pos + PCI_EXP_LNKCTL, &reg16);
>>         reg16 &= ~state;
>>         pci_write_config_word(pdev, pos + PCI_EXP_LNKCTL, reg16);
>>
>>         if (!pdev->bus->self)
>>                 return;
>>
>>         pos = pci_pcie_cap(pdev->bus->self);
>>         pci_read_config_word(pdev->bus->self, pos + PCI_EXP_LNKCTL, &reg16);
>>         reg16 &= ~state;
>>         pci_write_config_word(pdev->bus->self, pos + PCI_EXP_LNKCTL, reg16);
>> }
>> #endif
> 
> No, I mean __e1000e_disable_aspm is called from several spots:
> 
> *** drivers/net/e1000e/82571.c:
> e1000_get_variants_82571[435]  e1000e_disable_aspm(adapter->pdev, PCIE_LINK_STATE_L0S);
> 
> *** drivers/net/e1000e/netdev.c:
> e1000_change_mtu[5027]         e1000e_disable_aspm(adapter->pdev, PCIE_LINK_STATE_L1);
> __e1000_resume[5402]           e1000e_disable_aspm(pdev, PCIE_LINK_STATE_L1);
> e1000_io_slot_reset[5650]      e1000e_disable_aspm(pdev, PCIE_LINK_STATE_L1);
> e1000_probe[5797]              e1000e_disable_aspm(pdev, PCIE_LINK_STATE_L1);
> 
> Are all of them safe for the unlocked version of ASPM disable?

yes, there are two version __e1000e_disable_aspm(), one is when aspm support is compiled in, and another one is not.

the one without aspm compiled does not use pci_bus_sem in it self...

So I assume another path should not use pci_bus_sem in the function itself.

Yinghai

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