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 circumstance. 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
