simple-pm-bus driver

[oskar.holmlund_ohdata.se]

Summary

Add a simple-pm-bus driver to get AM335x to boot.
If the DTS node contains a clock it will be enabled later in the boot process.

[oskar.holmlund_ohdata.se]

D27889 are required to get AM335x to boot.

[manu]

Any reason the clock are enabled after interrupts ? I suspect that some stuff will rely on the clock being activated at attach.
The bindings have this comment :

Hence, the bus controller's PM domain and/or
clock must be enabled for child devices connected to the bus (either
on-SoC or externally) to function.

It also seems that some TI nodes doesn't respect the bindings as they have no clocks or power-domain property, are we relying on u-boot for those to work ?

sys/dev/fdt/simplepmbus.c

105

Doesn't seems to be true, I think we can have multiple clocks.

[manu]

sys/dev/fdt/simplepmbus.c

113

I've missed that the first time, any reason we don't enable the clock directly ?

[manu]

So, apparently the goal of simple-pm-bus is only to enable runtime pm in the Linux kernel for the whole child tree, while simple-bus doesn't do that.
Apparently the bindings are wrong suggesting that either power-domain or clock is required and the Linux code seems to indicate this ...