On Wed, Jan 29, 2014 at 06:00:26PM +0800, xinhui.pan wrote: > > > 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@xxxxxxxxx> > >>> > >>> 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@xxxxxxxxx> > >>> Signed-off-by: xinhui.pan <xinhuix.pan@xxxxxxxxx> > >>> --- > >>> 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. To be honest, I don't know ;-) > > 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. OK, so if this is not a problem, I would suggest keeping the code as is for now as someone who introduced the pm_schedule_suspend() thing probably tested it and it worked then. In fact, I think that the PCI part of that driver needs an audit since it does some PCI power management magic itself which drivers aren't supposed to do anymore. -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
