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SubjectRe: [PATCH] i2c-designware-pcidrv: fix the incorrect return of idle callback


于 2014年01月29日 16:35, Mika Westerberg 写道:
> On Tue, Jan 28, 2014 at 07:30:35PM +0100, Wolfram Sang wrote:
>> On Tue, Jan 28, 2014 at 01:48:28PM +0800, xinhui.pan wrote:
>>> From: "xinhui.pan" <xinhuix.pan@intel.com>
>>>
>>> i2c_dw_pci_runtime_idle should return -EBUSY rather than zero if it do success.
>>
>> I don't understand...
>>
>>> Otherwise rpm_idle will call pm_suspend again and that may cause pm_schedule_suspend delay invalidate.
>>>
>>> Signed-off-by: bo.he <bo.he@intel.com>
>>> Signed-off-by: xinhui.pan <xinhuix.pan@intel.com>
>>> ---
>>> drivers/i2c/busses/i2c-designware-pcidrv.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/i2c/busses/i2c-designware-pcidrv.c b/drivers/i2c/busses/i2c-designware-pcidrv.c
>>> index f6ed06c..96e81f6 100644
>>> --- a/drivers/i2c/busses/i2c-designware-pcidrv.c
>>> +++ b/drivers/i2c/busses/i2c-designware-pcidrv.c
>>> @@ -190,8 +190,8 @@ static int i2c_dw_pci_runtime_idle(struct device *dev)
>>> int err = pm_schedule_suspend(dev, 500);
>>> dev_dbg(dev, "runtime_idle called\n");
>>>
>>> - if (err != 0)
>>> - return 0;
>>> + if (err)
>>> + return err;
>>> return -EBUSY;
>>
>> ... it does return EBUSY when pm_schedule_suspend() succeeds? It only
>> returns 0 if it does not succeed (for which I don't know if this is an
>> apropriate behaviour). Mika?
>
> If I understand correctly, pm_schedule_suspend(dev, 500) is there because
> we want to runtime suspend in 500 ms. It then returns -EBUSY to prevent PM
> runtime from carrying on suspend on it's own. However, I have no idea where
> this magical 500 ms requirement comes from.
>
> If we fail to schedule suspend we let the PM core to do whatever it thinks
> suitable (in this case I suppose it suspends the device).
>

Hi ,Mika
If the callback returns 0,it means pm_schedule_suspend fails,
also means rpm_check_suspend_allowed(pm_schedule_suspend calls it)
returns nonzero value.As a result,rpm_suspend will be called by rpm_idle.
However in rpm_idle, rpm_check_suspend_allowed is called at first,too.
and the return value is treated as it is.But rpm_idle just returns
without doing anything(rpm_suspend is not called).
in both case above,why goes in different ways? I am confused.

> I think the whole idle dance could be replaced with a use of runtime PM
> autosuspend, just like we do in the platform version of the driver.
>
> Xinghui,
>
> Is this a real problem that you are trying to solve?
>

To be honest,we got many panic when testing.
But is not caused by this driver I think.
while checking problems,we found these confusing codes by accident.

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