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. Last time I checked the PM domain code didn't seem like a good fit. I'll go recheck and see if I can make it work. One minor issue with putting the driver in drivers/power is that that directory is only built when POWER_SUPPLY is selected. And since this isn't really a power supply driver at all, either we need to change the drivers/Makefile to descend unconditionally or we need to find another home. I'll see if I can come up with yet another generic binding for this in an attempt to move this out of arch/arm/mach-tegra... > > Also, the real win we get from moving code out into drivers/ is if we > > can provide a common framework for them. I don't see how we can possibly > > do that for this code since there simply isn't enough commonality > > between SoCs. At the same time we now have a situation where both 32-bit > > and 64-bit variants of some SoCs share some of the same hardware at the > > very low level and since we don't have mach-* directories for 64-bit ARM > > and shouldn't be duplicating code either, we need to find a new home for > > this type of code. drivers/soc seemed to fit perfectly well. > > For the low-level stuff yes, but I agree with Santosh there needs to be > some more work trying to split out individual high-level drivers. > > There are two common patterns for the interface between the low-level > register access and the more high-level stuff: you can either use > a "syscon" driver that just exports a struct regmap and that gets referenced > from other drivers using a phandle in their device nodes, or you have > a driver in drivers/soc that exports a somewhat higher-level interface > and comes with its own header file that gets included by other drivers. > At the moment, the syscon/regmap variant can only be used once device > drivers are loaded, but there is some broad agreement that it should > be changed to allow calling syscon_regmap_lookup_by_phandle() at > early boot using just DT accessors. Note that we already have all these drivers and they do work for earlier Tegra generations. My attempt to move these out of arch/arm/mach-tegra is merely about being able to share them with upcoming 64-bit variants. So it's not about adding new functionality but rather about keeping the existing level of functionality on 64-bit. I'm not a fan of the syscon/regmap approach at all and the existing drivers use a higher-level API already, so I think we're going to stick with that. Thierry
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