On Tuesday, November 26, 2013 01:41:13 PM Mike Qiu wrote: > On 11/14/2013 04:54 PM, Huang Ying wrote: > > On Thu, 2013-11-14 at 16:37 +0800, mike wrote: > >> On 11/14/2013 04:25 PM, Huang Ying wrote: > >>> On Thu, 2013-11-14 at 16:12 +0800, mike wrote: > >>>> On 11/14/2013 03:53 PM, Huang Ying wrote: > >>>>> On Thu, 2013-11-14 at 15:19 +0800, mike wrote: > >>>>>> On 11/14/2013 01:59 PM, Huang Ying wrote: > >>>>>>> On Thu, 2013-11-14 at 11:23 +0800, mike wrote: > >>>>>>>> On 11/14/2013 03:20 AM, Alan Stern wrote: > >>>>>>>>> On Wed, 13 Nov 2013, Bjorn Helgaas wrote: > >>>>>>>>> > >>>>>>>>>> [+cc Rafael, linux-pm] > >>>>>>>>>> > >>>>>>>>>> On Wed, Nov 13, 2013 at 6:09 AM, mike<qiudayu@xxxxxxxxxxxxxxxxxx> wrote: > >>>>>>>>>>> Hi Huang Ying, > >>>>>>>>>>> > >>>>>>>>>>> I see you are the author of this patch, commit id is: > >>>>>>>>>>> 967577b062417b4e4b8e27b711220f4124f5153a > >>>>>>>>>>> > >>>>>>>>>>> I have a question while I try to understand this patch, > >>>>>>>>>>> So I would very grateful if you or others can give me some reply..... > >>>>>>>>>>> > >>>>>>>>>>> ............ > >>>>>>>>>>> - rc = ddi->drv->probe(ddi->dev, ddi->id); > >>>>>>>>>>> + pm_runtime_get_sync(dev); > >>>>>>>>>>> + pci_dev->driver = pci_drv; > >>>>>>>>>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^ > >>>>>>>>>>> I see here you make the driver to initialize before probe, > >>>>>>>>>>> But I have no idea of why you do this change..... > >>>>>>>>>>> > >>>>>>>>>>> and I look inside the code, it may be pm_runtime relate?? > >>>>>>>>> Yes, it is related to runtime PM. In the PCI subsystem, runtime PM > >>>>>>>>> doesn't do anything unless pci_dev->driver is set. You can see this at > >>>>>>>>> the start of pci_pm_runtime_suspend(). > >>>>>>>>> > >>>>>>>>> Since we want the driver's probe routine to be able to carry out > >>>>>>>>> runtime PM operations, we have to set pci_dev->driver before the probe > >>>>>>>>> routine runs. > >>>>>>>> Is there any situations , like in probe state, pci_dev->driver > >>>>>>>> has been set. the pci_pm_runtime_xxx() has passed > >>>>>>>> pci_dev->driver NULL check, but at this point, probe fail > >>>>>>>> occurs, and pci_dev->driver to be set to NULL. > >>>>>>>> > >>>>>>>> What will happen ? Or this situation will never happen? > >>>>>>>> I'm confuse about this. > >>>>>>> I think that will never happen. Before ->probe(), pm_runtime_get_sync() > >>>>>>> is called, so pci_pm_runtime_xxx() will not be called until > >>>>>>> pm_runtime_put_noidle() is called in ->probe(). And > >>>>>>> should be done as one of the latest actions in > >>>>>>> ->probe(), after the normal probe actions succeeded. > >>>>>> OK, just as your description, it seems OK. > >>>>>> But this is really a issue as I explained in last email. > >>>>>> > >>>>>> So I want to know if there are any side-effect of changing the code > >>>>>> in pci_pm_runtime_xxx() > >>>>>> > >>>>>> if (!pci_dev->driver) > >>>>>> return 0; > >>>>>> to > >>>>>> > >>>>>> if (!dev->driver) > >>>>>> return 0; > >>>>>> > >>>>> If you make this change, we can not put devices into low power state > >>>>> (runtime suspend the device) in ->probe(). That is expected in some > >>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > >>>> This means dev->driver is NULL ?? but pci_dev->driver is set??? > >>>> > >>>> Because if use pci_dev->driver can put into low power state, means > >>>> > >>>> pci_dev->driver is set, but in the situation, use dev->driver will can't, > >>>> > >>>> means dev->driver = null, but I have not find any case that > >>>> > >>>> dev->driver = null, but pci_dev->driver != null; > >>> Sorry I make a mistake here. The dev->driver != null in > >>> local_pci_probe(). We use pci_dev->driver instead of dev->driver in > >>> pci_pm_runtime_xxx() because we want device to be kept in normal power > >>> state (D0) and SUSPENDED state when unbound.The > >>> pm_runtime_put/get_sync in pci_device_remove/local_pci_probe will not > >>> change the power state of the device because of the check in > >>> pci_pm_runtime_xxx(). > >> Yes, you are right, but what am I confuse is that, why check dev->driver > >> in pci_pm_runtime_xxx() can't keep the device in normal power > >> state (D0) and SUSPENDED state when unbound. > >> > >> May be logic issue ? > > Because dev->driver is set before local_pci_probe() and cleared after > > pci_device_remove(). But we need a flag to be changed in > > local_pci_probe() and pci_device_remove(). > Hi Ying, > > I'm now face one bug, and the root cause is this logic has some problem. > > The other component calls the ops in driver during probe state, which a > lot of critical data struct haven't been setup yet. > > This never happen in old logic, because dev->driver is unset in probe > state, it can check dev->driver to see if the device diver can work. But > for new logic it is really a big issue. What is the other component and why is it doing that? Checking dev->driver may not be a correct way to address this issue anyway. Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
