Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: Allowing reset controllers before SMP initialization (on ARM)? | Date | Sat, 18 Apr 2015 21:38:53 +0200 |
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On Thursday 16 April 2015 11:42:08 Maxime Coquelin wrote: > Hi Florian, Arnd, > > On 04/16/2015 10:04 AM, Arnd Bergmann wrote: > > On Wednesday 15 April 2015 17:51:18 Florian Fainelli wrote: > >> Hi, > >> > >> In order to support initialization of the secondary core on BCM63138 > >> SoCs, I would want to utilize a reset controller to release the > >> secondary CPU from reset [1]. > >> > >> Here are multiple options: > >> > >> - expose a custom function which registers the reset controller platform > >> driver as early as possible, which is probably acceptable, but also > >> requires the DT machine descriptor to populate the platform bus earlier, > >> which we could completely avoid > > I think populating the platform bus earlier is not realistic, that > > would break lots of existing dependencies. In particular, we can't > > do it much earlier because it has to be done after the platform bus > > itself is instantiated. > > > >> - have a OF_DECLARE_RESET_CONTROLLER() which is running fairly early > >> during boot, such that we can utilize reset controllers are early as > >> possible, before any initcall level, and before SMP initialization is > >> kicking in > > We've added a couple of those, and it could be done here, but putting > > them in the right order is a bit tricky, and I think we can avoid it. > > I have already proposed a OF_DECLARE_RESET_CONTROLLER() implementation: > https://lkml.org/lkml/2015/2/20/395 > > I needed it for the STM32 timers, but it was not accepted. > Now, I perform the timers reset in the bootloader, but it shouldn't work > in your case.
I guess if there is enough interest in this, we will eventually do it. This is something we can change at any time without user-visible changes or DT binding changes. The tradeoff is mainly that without OF_DECLARE_RESET_CONTROLLER(), we need a couple of hacks in early init code, while adding too many of those OF_DECLARE_*() macros has the risk that we won't be able to order them in a sane way that works on all platforms, so I'm always reluctant about adding an extra one.
Arnd
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