> > > > Yes, but the problem is that you also need clocks and reset of other modules > > in the same domain to safely control the domain's status. Eg: the ISPs, VI and > > CSI share a domain. VI and CSI are useable without ISP and the ISP lacks > > public documentation. So it's not unlikely a VI and CSI driver will upstreamed > > someday which means we would need to control the domain and therefore would > > need to tell that driver about the ISPs clocks and resets even though the > > driver doesn't know anything about the ISP hw otherwise. > > Can't we make powergates reference counted so that they don't get > disabled as long as there are any users? Looking for example at the We could, but then why not switch to the powerdomain code and make powering off a domain a NOP until we sorted out the context save/restore or fixed the framework to allow for suspend without turning off the domains? > display controller driver, modules don't seem to care overly much about > the powergate's state except that it needs to be turned on before they > touch some of the registers. > > From a bit of experimentation it also seems like the sequence encoded > within tegra_powergate_sequence_power_up() isn't at all necessary. I > couldn't find an authoritative reference for that either, so I'm tempted > to conclude that it was simply cargo-culted from the dark-ages. > > So I'm thinking that if we ever move to use power domains for this, we > may be able to just drop any extra handling (well, we'd need to keep it > for backwards-compatibility... *sigh*) and let drivers handle the clock > and reset resources. > > On the other hand, given that we already need to keep the existing code > for backwards-compatibility, I'm not sure there's a real advantage in > turning them into power domains, since we'd be adding extra code without > an clear gains (especially since it seems like we'd need even more code > to properly handle suspend/resume in drivers that need powergates). > Unless we fix the framework to require context save/restore for suspend. There is a good reason to do that. context save/restore requires energy as well, so it's not a given that turning off domains in system suspend will save power. 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
