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(). > I know I always been a question guy, i apologize for spend a lot > time to reply this mail, but I really want to understand it, Never mind. Best Regards, Huang Ying -- 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
