On 14/05/2015 15:59, Viresh Kumar wrote: > On 14 May 2015 at 18:36, Mason wrote: >> When I execute "echo 18500 > scaling_max_freq" >> the system is supposed to change the CPU frequency to 18.5 MHz >> (I might have a bug lurking there) and PERIPHCLK is 1/2 of that, >> i.e 9.25 MHz. > > So at least we are on the right path. But it looks to me that this > call is not getting propagated well. > > From the attachment you gave initially, the event handler for > twd-timers is: tick_handle_periodic(). i.e. you are running in > periodic mode and not one-shot... why ? I don't know. Is it not obvious (to someone who knows what to look for) from reading the smp_twd.c source? How do I run the TWD in one-shot mode? >> Yes, I do, but I was trying to use as much generic code as >> possible to limit the chances of introducing bugs. > > Hmm.. > >> I'll take a fresh look at the ARM GLOBAL TIMER, but last I >> checked, it didn't seem to handle frequency scaling. > > why is that required? Why will you change its freq ? http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0407g/CIHGECHJ.html "The global timer is clocked by PERIPHCLK." PERIPHCLK = CPUCLK/2 Change the CPUCLK, change the PERIPHCLK. > The same timer is probably used for SPEAr (the platform > I used to work on): > > http://lxr.free-electrons.com/source/arch/arm/mach-spear/time.c?v=3.14 Did that platform use cpufreq DFS? Regards. -- 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
