Re: AM335x mpurate + bogomips

[Frank Agius <ftagius@yahoo.com>]

On 2/21/2013 11:36 AM, Mark Jackson wrote:
> Before I dig any deeper, can anyone tell me if the bootarg "mpurate" is meant to
> be supported for AM335x SoCs ?
>
> I've tried it on our custom board using 3v8, but no joy.
>
> The boot log shows:-
>
> [    0.000000] Booting Linux on physical CPU 0x0
> [    0.000000] Linux version 3.8.0-03059-g621553c-dirty (mpfj@mpfj-nanobone) (gcc version 4.5.4 (Buildroot 2012.11) ) #113 SMP Thu Feb 21 16:29:48 GMT 2013
> [    0.000000] CPU: ARMv7 Processor [413fc082] revision 2 (ARMv7), cr=10c53c7d
> [    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
> [    0.000000] Machine: Generic AM33XX (Flattened Device Tree), model: Newflow NanoBone
> [    0.000000] Memory policy: ECC disabled, Data cache writeback
> [    0.000000] CPU: All CPU(s) started in SVC mode.
> [    0.000000] AM335X ES1.0 (neon )
> ...
> [    0.000000] Kernel command line: console=ttyO0,115200n8 mpurate=720 root=/dev/mmcblk0p2 ro rootfstype=ext2 rootwait
> ...
> [    0.001119] Calibrating delay loop... 364.48 BogoMIPS (lpj=1425408)
>
> I have seen other boot logs outputs [1] from other people where they are getting nearly double that.
>

I have also observed a drop in the reported BogoMIPS value when using 
the latest kernel.  Previously (with a 3.5 kernel) the BogoMIPS value 
was approximately equal to the CPU frequency. I finally found the reason 
for the BogoMIPS change:

http://www.spinics.net/lists/arm-kernel/msg221672.html

It looks like BogoMIPS reporting changed because of the delay routine 
patch introduced in 3.6.  So the change in BogoMIPS is real, but should 
not be a concern.

frank agius