Stephen Boyd wrote:
Mason wrote:config HAVE_ARM_TWD bool depends on SMP select CLKSRC_OF if OF help This options enables support for the ARM timer and watchdog unit One problem I see is that HAVE_ARM_TWD depends on SMP... One of the systems I want to support is UP (single-core Cortex A9). Does that mean I should use an SMP kernel even for that system? Or is there a different subsystem for UP systems?I don't see any problem with the TWD dropping the dependency on SMP. The code should work the same on a UP configuration and if that's the only timer you have that can deliver interrupts to your processor then it would be required. You'd still need a clocksource though, which the TWD doesn't provide.
I want to use as much mainlined code as possible. Thus, this means (if my reasoning is not flawed) that I should use standard ARM "services" (can't think of a better term) for which code is already available in the kernel. As for clock events, IIUC, I can choose either TWD or the global timer (with a slight advantage to TWD). Are there other options? (I probably have some platform-specific infrastructure available, but I'm asking about standard support.) My platform provides a 32-bit counter, ticking at a constant 27 MHz. Reading this counter has a latency of roughly 70 ns (it has to go over the system memory bus). I think this is good enough for both the clock source and sched_clock, is it not? So the plan would be: - clocksource and sched_clock : 27 MHz, 32-bit counter, platform - clockevents : TWD, standard Regards. For my own reference http://elinux.org/Kernel_Timer_Systems http://thread.gmane.org/gmane.linux.kernel/1062438 (not merged) Message-ID: <20150206191419.GA8656@xxxxxxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
