[U-Boot] [PATCH] ARM: tegra: Define Tegra20 CAR binding

[Stephen Warren]

Peter De Schrijver wrote at Tuesday, January 24, 2012 2:53 AM:
> What about the peripheral resets which are also handled by CAR? Peripheral
> clock nodes also offer assert and deassert methods for the reset signal
> associated with them. Those methods are used when powergating domains for
> example. Should we model this in the same binding?

In most cases, I think the resets are handled purely within clock enable
and disable, so there's no need to explicitly manage them or represent
them in the device tree. Do you agree here?

I recall that you mentioned some power-management code might need to
manage reset separately though. Can you explain why a module would be
reset separately from disabling the clocks though?

If we do need this, I think we can just add a property to the node of
each device that needs such explicit management. Something like:

tegra_car: clock at 60006000 {
    compatible = "nvidia,tegra20-car";
    ....
};

foo at 70007000 {
    compatible = "nvidia,tegra20-foo";
    regs = <...>;
    nvidia,car-reset-id = <&tegra_car 30>;
};

And the driver for "foo" can ignore cell 0, and extract the cell 1 and
pass the value to tegra_periph_reset_assert().

I'd expect to put the CAR phandle into the property in case we ever get
a more generalized reset subsystem, and need more general code to
interpret the property. I did the same for the Tegra APB DMA controller
client binding where clients need to know the "DMA select" value.

Does that all seem reasonable?

-- 
nvpublic