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

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Date:	Wed, 11 May 2011 13:23:21 -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 05/09/2011 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



> 
>> +extern void __pci_disable_link_state(struct pci_dev *pdev, int state);
>>  extern void pcie_clear_aspm(void);
>>  extern void pcie_no_aspm(void);
>>  #else
> 
> pci_disable_link_state_locked would be more descriptive and would match
> other usage in the kernel.

ok.

Thanks

Yinghai
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