On Wed, Feb 08, 2012 at 12:43:51PM -0800, Paul Zimmerman wrote: > > From: Felipe Balbi [mailto:balbi@xxxxxx] > > Sent: Tuesday, February 07, 2012 10:15 PM > > > > On Tue, Feb 07, 2012 at 02:19:49PM -0800, Paul Zimmerman wrote: > > > > > > > > OK, I will poke around and see if I can find an existing driver to use as > > > > an example. > > > > > > Hi Felipe, > > > > > > Can you explain a little about how the runtime_pm stuff will work in > > > the DWC3 driver, disregarding the HAPS platform for now. > > > > > > For example, if the device is a PCI device, won't the PM ops need to > > > be part of the struct pci_driver in the dwc3-pci module? > > > > > > If so, how will they be able to communicate with the routines in the > > > dwc3 module? Or if not, how will that work exactly? > > > > Ok, the way it works is that the e.g. PCI device is a parent device to > > the DWC3. So, in fact, you will end up with two pm ops: one that only > > knows about DWC3 and one that only knows about PCI. > > > > The pm core guarantees that parent's e.g. runtime_suspend(), will only > > be called after all children (in this case, only one) are suspended. > > Likewise for resume. > > > > So, what we need to do is to make one pm ops that knows everything the > > power management features on DWC3 and another which knows about PCI, > > then hook them up properly and whenever pm usage counter reaches zero, > > dwc3's runtime_suspend() is called, then after that dwc3-pci's > > runtime_suspend() will be called. > > Thank you! That was the piece of the puzzle that was missing. OK, > I'll take a crack at implementing the pm ops for dwc3 and dwc3-pci. no problem ;-) There's very good documentation under Documentation/power/ and the folks at linux-pm@vger are very helpful too ;-) > > Just keep in mind that glue layer also needs to keep track of its own > > usage counters, what I mean by that, is that on dwc3-pci probe you > > should probably call pm_runtime_get_sync() and right before returning > > from probe, you call pm_runtime_put(). This will make sure that the PCIe > > device is powered up when you need and can be autosuspended when you > > don't need it anymore. > > I see that Alan had a correction to this part in a later email. Indeed, I was not aware of the PCI differences :-) I will take care of that on the dwc3-omap.c though ;-) thanks -- balbi
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