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

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Date:	Thu, 12 May 2011 16:32:10 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Yinghai Lu <yinghai@...nel.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 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?

-- 
Jesse Barnes, Intel Open Source Technology Center
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