Subject: Delays, clocks, timers, hrtimers, etc

From: [email-masked] (Mason)
Date: Mon, 09 Feb 2015 15:27:39 -0800

Russell King - ARM Linux wrote:

> Mason wrote:
>  
>> Q1. the {n,u,m}delay function family
>>
>> [...]
>
> Timers are preferred because of the problems with the software delay loop.

Can you confirm that if one intends to use timer-based delays, one must
call register_current_timer_delay at init?

There aren't many callers of register_current_timer_delay.

   arch/arm/kernel/arch_timer.c:   register_current_timer_delay(&arch_delay_timer);
   arch/arm/mach-u300/timer.c:     register_current_timer_delay(&u300_delay_timer);
   drivers/clocksource/nomadik-mtu.c:      register_current_timer_delay(&mtu_delay_timer);

Does that mean that every other platform is using software delay-loops
instead of timer-based delay-loops?

(AFAIU, architected / generic timers are new-ish in Cortex A7 and A15.)

Regards.