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Linux/TMS320DM8148: Different clock rate in u-boot and Linux

ranchu
Guru 20755 points
Part Number: TMS320DM8148

Tool/software: Linux

Hello,

We recently noticed that there are different clock rate observed in linux compared to u-boot.

In u-boot we see:


U-Boot 2010.06-dirty (Dec 26 2016 - 10:37:28)

TI8148-GP rev 3.0

L3 clk : 200MHz
IVA clk : 410MHz
ISS clk : 480MHz
DSP clk : 750MHz
DSS clk : 200MHz
ARM clk : 720MHz
DDR clk : 400MHz

While in linux with cpuinfo or sysfs entries we see 1GHz rate.

The chip revision should be limited to 720Mhz.

1. How is it that the clock rates is different ?

2. We tried to change rate to 600MHZ with sysfs scaling_setspeed , but it fails to change to 600M (although it appears in sysfs entry for available frequencies)

Thank you,

Ran

  • 0
    Intellectual 690 points

    Hi Ran,

       I think DVFS is enabled in your case, which might have changed the CPU frequency. What is your current governor?

    It should be userspace governor in order to change the frequency from sysfs interface.

      If the issue still persists, please provide the dmesg logs and config file.

  • 0 in reply to sai prasad
    Guru 20755 points
    Hi Sai,

    Thank you for the feedback.

    If I'll use userspace governer, will it provide other available frequencies (now we only have 600000 and 1000000), I wanted to change to other frequencies as well.
    Is it possible ?

    Thank you very much,
    Ran
  • 0 in reply to ranchu
    Intellectual 690 points

    Hi Ran,

         Yes, we can change to other frequencies also. We have to add/enable OPP's(operation points). But be cautious, enabling or adding other OPPs may cause system instability.

    What's the Linux kernel version ? If it is 2.6 then check arch/arm/mach-omap2/opp814x_data.c for supported OPP's. If it is greater than 3.7 then check corresponding dtsi file.

  • 0 in reply to sai prasad
    Guru 20755 points
    Sai,
    Thank you very much