On Fri, 2016-03-11 at 09:00:14 +0100, Mike Looijmans wrote:
> On 11-03-16 07:44, Mike Looijmans wrote:
> ...
> >The 'prescaler hack' is apparently still present in the 4.4 kernel code. The
> >problem is that it no longer works, not even on the speedgrade 1 devices
> >(with
> >only 333 and 666 MHz setpoints).
>
> Did a quick test on the board. The prescaler is applied correctly, so what's
> causing the trouble?
>
> # devmem 0xF8001000
> 0x00000015
> # echo 333333 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
> # devmem 0xF8001000
> 0x00000013
> # echo 666666 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
> # devmem 0xF8001000
> 0x00000015
>
> Bits 1..4 are the prescaler values, at 666 it's set to 0b111 (7) and at 333
> it's set to 0b110 (6). The register is a power-of-two value, so "7" means
> 2^8 and "6" means 2^7.
Are you sure the kernel is using the TTC and not GT? Especially on ARM
multi-arch kernels, the GT driver tends to be included in the kernel
and it will be used if available as the GT is the "better" clocksource,
compared to TTC.
Sören
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