On Wednesday, September 6, 2017 3:59:16 PM CEST Ulf Hansson wrote: > On 6 September 2017 at 12:46, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: > > On Wednesday, September 6, 2017 2:52:59 AM CEST Rafael J. Wysocki wrote: > >> On Monday, September 4, 2017 2:55:37 PM CEST Ulf Hansson wrote: > >> > [...] > > > > I guess I can wrap it up, because all of the points seem to have been stated > > and repeating them would not be useful. > > > > My summary of the discussion is as follows. > > > > It only is valid to use pm_runtime_force_suspend/resume() as *driver* > > callbacks for system suspend/resume if both the driver itself and all of > > the middle layers it has to work with carry out the same sequence of > > operations in order to suspend the device both in runtime PM and for > > system sleep (and analogously for resuming). [The middle layers need > > to meet additional conditions, but that's less relevant.] > > > > Unfortunately, for the ACPI PM domain and the PCI bus type the situation is > > different, because they generally need to do different things to suspend > > devices for system sleep than they do for runtime PM (which mostly is > > related to the handling of ACPI-defined sleep states and device/system > > wakeup, but not limited to that). This clearly means that drivers needing > > to work with the ACPI PM domain and PCI drivers cannot use > > pm_runtime_force_suspend/resume() as their PM callbacks for system > > suspend/resume (quite fundamentally). > > > > [Note that for i2c-designware-platdrv the situation is even more complicated, > > because on some platforms it has to work with the ACPI PM domain (or the > > ACPI LPSS driver), on some platforms its parent is a PCI device and on > > some other platforms there's none of them.] > > That is also why it makes it really interesting. I am guessing we will > be seeing more of these cases sooner or later. > > To make it even more complex, I can guess we can expect cases when > genpd is mixed with the ACPI PM domain. > > > > > However, for drivers that need to work with the ACPI PM domain and > > PCI drivers the differences in the device handling between runtime PM and > > system suspend/resume are *very* often (even though not always) covered > > entirely by the middle layer code. Then, the driver itself actually > > always carries out the same sequence of operations in order to suspend > > the device (or to resume it, analogously). The driver then can re-use > > its runtime PM callbacks for system suspend/resume (but at the driver > > level only) and it would be good to make that easy (or easier) for these > > drivers somehow. > > This is a very nice summary so far, thanks for putting it together. No problem. I actually have an idea on how to move forward, but let me start a new thread for discussing that. Thanks, Rafael
