On Mon, Jun 30, 2014 at 09:21:22PM +0200, Thierry Reding wrote: > * PGP Signed by an unknown key > > On Mon, Jun 30, 2014 at 09:20:30AM +0200, Arnd Bergmann wrote: > > On Saturday 28 June 2014 22:40:26 Thierry Reding wrote: > > > > > pmc.c implements various routines to access the power management > > > > > controller, some of which is needed by suspend/resume, some of it is > > > > > needed by SMP. powergate.c implements a subset of the PMC that needs to > > > > > be exported to drivers to enable power partitions on the SoC. I'm not > > > > > aware of subsystems that deal with this kind of driver. > > > > > > > > > Please see above. > > > > > > Like I said, I don't see what business suspend/resume related code has > > > in drivers/power. What we're talking about here really is functionality > > > very specific to Tegra. Also some of that code needs to be run at very > > > early points in the boot process, so we can't reasonably turn it into a > > > proper driver anyway. > > > > I believe the powergate.c stuff can be changed into pm_domain code, but > > we don't have a good subsystem with generic DT bindings yet, so that > > may need some more groundwork first. drivers/power or a subdirectory > > of that may end up being the right place though. > > So I ended up implementing the powergates as generic_pm_domain, but that > breaks existing drivers currently. The reason is that generic_pm_domains > are automatically turned off on suspend and turned back on on resume. On > Tegra if a partition is powered off then the whole module looses state > and would need to be completely reinitialized. None of the drivers > currently support that and I'm also not sure if it's really what we want > since it means for example redetecting links and reenumerating devices > on PCI, or probing display outputs in DRM. That's going to take a lot of > time and may not be appropriate for suspend-to-RAM. > > Unfortunately I haven't found a way to force a domain to remain powered > during suspend/resume. If we make power off a NOP until LP0 gets implemented? Then device state will have to be saved/restored. Cheers, Peter. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
