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RFC Consolidation: move SMP local timers to driver/clocksource

Marc Zyngier linux-arm-kernel 1 version New

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  1. v1 RFC Latest0 of 16 patches 0 repliesNew

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Cover letter [RFC PATCH 00/16] Consolidation: move SMP local timers to driver/clocksource
Quoted 11 lines · Rob Herring

Marc,

Quoted 8 lines · Marc Zyngier
Quoted 2 lines · Rob Herring

Also, device tree support for early platform devices would be useful for this.

What about the attached patch? I've used it to boot a VExpress board with the following DT snippet (and the corresponding support in the amp_smp_twd driver):

Quoted 7 lines
Quoted 2 lines
	localtimer at 2c000600 {
		device_type = "localtimer";

My understanding is device_type is only supposed to be used for devices with real OpenFirmware. You could just add localtimer or timer as a 2nd compatible string. I think localtimer is a bit of a Linux name, so just timer may be better.

Using "compatible" would not work. You'd have to add the same compatible string to all drivers, and get drivers probing the wrong device. Any other property we could use instead?

As for the "localtimer" string, this is to differentiate the per-cpu timers versus the global timers, and they may need to be probed in a specific order (global first, and then local).

The reason for this is that TWD needs to be calibrated, hence the need for a global timer running. Colin's patch could help getting rid of this restriction though.

	M.
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Jazz is not dead. It just smells funny...

Read the cover letter in its thread