On Thu, Jan 15, 2015 at 3:55 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote:
> [+cc Rafael, Pavel, linux-pm]
>
> On Wed, Jan 14, 2015 at 09:36:48PM -0800, Yinghai Lu wrote:
>> Wilmer reported continuous suspend/resume does not work after
>> commit 928bea964827 ("PCI: Delay enabling bridges until they're needed").
>>
>> For pci bridge without driver, FW enable it already.
>> In pci_pm_resume/pci_pm_reenable_device after first resume
>> will not reenable the device, aka the status is not the same
>> as that before first suspend.
>>
>> Try to update enable status according to register value before
>> calling pci_reenable_device, so we will not miss those pm
>> operation calling for next suspend/resume.
>>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=86421
>> Fixes: 928bea964827 ("PCI: Delay enabling bridges until they're needed")
>> Reported-by: Wilmer van der Gaast <kernel@xxxxxxxxxxxxxxxx>
>> Bisected-by: Wilmer van der Gaast <kernel@xxxxxxxxxxxxxxxx>
>> Tested-by: Wilmer van der Gaast <kernel@xxxxxxxxxxxxxxxx>
>> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
>> Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
>> CC: stable@xxxxxxxxxxxxxxx # v3.10+
>
> 928bea964827 appeared in v3.12. Did you mean v3.12+ instead of v3.10+?
Yes.
get confused that Wilmer can not use 3.10 stable kernel.
>
> I'd really like to get Rafael and Pavel to take a look at this.
>
>> ---
>> drivers/pci/pci-driver.c | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
>> Index: linux-2.6/drivers/pci/pci-driver.c
>> ===================================================================
>> --- linux-2.6.orig/drivers/pci/pci-driver.c
>> +++ linux-2.6/drivers/pci/pci-driver.c
>> @@ -519,8 +519,17 @@ static void pci_pm_set_unknown_state(str
>> */
>> static int pci_pm_reenable_device(struct pci_dev *pci_dev)
>> {
>> + u16 cmd;
>> int retval;
>>
>> + /* update enable_cnt according to cmd register */
>> + pci_read_config_word(pci_dev, PCI_COMMAND, &cmd);
>> + if (!pci_dev->is_busmaster && (cmd & PCI_COMMAND_MASTER))
>> + pci_dev->is_busmaster = true;
>
>
>> + if (!pci_is_enabled(pci_dev) &&
>> + (cmd & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY)))
>> + atomic_inc(&pci_dev->enable_cnt);
>
> This doesn't feel right because we're handling enable_cnt differently here
> than we do on initial boot.
>
> On initial boot, I don't think we set enable_cnt based on whether firmware
> left the IO or MEMORY bits set in the command register. Why should we
> modify enable_cnt based on the command register during resume?
>
> I could certainly believe we should do something during initial boot, too.
> It just seems like we should look at the command register in both places or
> neither place.
>
BIOS set power state correctly, so first suspend/resume will work.
late because setting power state will rely on the enable-cnt, first resume would
not set the power state related correctly, then second suspend/resume will not
work anymore.
will check if we can change to:
check hw status, and then enable the pci device on boot path instead.
Thanks
Yinghai
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