[U-Boot] [PATCH 0/3] arm: tegra20/colibri_t20: early pmic rail configuration

[Stephen Warren]

On 08/20/2015 04:59 PM, Marcel Ziswiler wrote:
> On 20 Aug 2015 21:58, Stephen Warren <swarren at wwwdotorg.org> wrote:
>
>  > Is there any guarantee that the voltage levels are high enough for the
>  > AVP to run correctly before the CORE rail is adjusted? It sounds to me
>  > like a HW design issue; the SoC reset output should reset the PMIC too.
>
> If by guarantee you mean whether it is impossible by software to
> completely screw the rail configuration no there is no such guarantee.
> But even on T30 where usually some PMIC GPIOs are used to switch to a
> sane default software could mess up the configuration of that as well.
> To prevent any of that I guess a higher level of trusted computing stuff
> would be required. At the end we just have to assume that regular DVFS
> operation should never leave it in a completely unbootable state.

That almost sounds like there's no need for this patch/series then, 
since we're assuming that SW won't leave the HW in a bad state. If SW 
can leave HW in a bad state, the only choice is to fix the issue in HW. 
However, perhaps you mean there are some states that are worse than 
others; we assume that the rails required for the AVP are always in a 
good state but the rails required for the CPU/CCPLEX may not be?