okenido
Posts: 24
Joined: Thu Aug 02, 2018 11:47 am

Setting ARM/core/RAM frequency has no effect

Wed Jan 09, 2019 11:56 am

Hello,

I'm using the mailbox interface of the RPI (https://github.com/raspberrypi/firmware ... -interface) in a bare metal app to change frequency settings of arm/core/ram but none of them seems to make the processing faster or slower.

Asking the mailbox for the current frequency returns the right values after I set them.

I wanted to do that since the default frequency reported by a mailbox call is 600Mhz for the ARM core and something like 250Mhz for the SDRAM... I read about topics saying that the CPU is in low-power state by default for bare metal apps. But no matter if I set 1.4Ghz or 100Mhz it seems to have no effect at all. (RPI 3B+)

Am i doing something wrong ?

LdB
Posts: 925
Joined: Wed Dec 07, 2016 2:29 pm

Re: Setting ARM/core/RAM frequency has no effect

Wed Jan 09, 2019 2:50 pm

The call works and as you are getting the current value (at least part of your code works) so all I can say is check your values/code
Tag id: 0x00038002
data size provided : 8
data_size response: 8,
clock id: 0x3
speed to set (1.2Ghz): 1200000
If you still have problems provided code, it would be a lot easier

Return to “Bare metal, Assembly language”