linux-kernel - Re: [PATCH] pci, e1000e: Add and use __pci_disable_link

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Date:	Thu, 12 May 2011 16:58:57 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	Greg Rose <gregory.v.rose@...el.com>,
	PJ Waskiewicz <peter.p.waskiewicz.jr@...el.com>,
	Alex Duyck <alexander.h.duyck@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Matthew Garrett <mjg@...hat.com>,
	Naga Chumbalkar <nagananda.chumbalkar@...com>,
	e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] pci, e1000e: Add and use __pci_disable_link_state

On 05/12/2011 04:32 PM, Jesse Barnes wrote:
> On Wed, 11 May 2011 13:23:21 -0700
> Yinghai Lu <yinghai@...nel.org> wrote:
> 
>> On 05/09/2011 02:35 PM, Jesse Barnes wrote:
>>> On Sun, 08 May 2011 11:54:32 -0700
>>> Yinghai Lu <yinghai@...nel.org> 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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