AM5728: How to modify cpu freq for Linux-RT

Shreek

Part Number: AM5728

Hello

I'm using AM5728 with PROCESSOR-SDK-LINUX-RT-AM57X 05_03_00_07, but I havn't found the cpu_freq governer under '/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor' like the Non-RT os. I found that the default freq for linux-rt is 1.5GHz and i just want it running at 1GHz. So, is there any way to set the freq to powersave mode (1GHz) for LINUX-RT?

over 4 years ago

0 Keerthy J over 4 years ago

TI__Guru**** 163100 points

Hi Shreek,

On RT-Linux CPUFREQ is disabled in Linux. Hence you are not seeing the /sys/devices/system/cpu/cpu0/cpufreq/* entries.

How did you figure out that the system is actually at 1.5G? Is it via DT or dynamically after booting Linux?

Regards,
Keerthhy

0 Shreek over 4 years ago in reply to Keerthy J

Intellectual 990 points

Hi Keerthhy,

Thanks for quick reply.

Actually I have tested the power dissipation and it is almost the same with the situation runing Non-RT Linux under OPP_HIGH(1.5GHz). Maybe it's not 1.5GHz, But I want to let the rt-linux runing at 1.0GHz for low power consideration, is there any way to fix it?

Best wishes!

Shreek

0 Keerthy J over 4 years ago in reply to Shreek

TI__Guru**** 163100 points

Shreek,

From the u-boot side. I see that AM5728 should be y default set to 1GHz.

arch/arm/mach-omap2/omap5/hw_data.c -

/* OPP NOM FREQUENCY for OMAP5 ES2.0, and DRA7 ES1.0 */
static const struct dpll_params mpu_dpll_params_1ghz[NUM_SYS_CLKS] = {

DRA7 also implies am5728 is also set to 1GHz by default at u-boot.

As long as kernel cpufreq framework is not interfering i expect the Kernel also to maintain what u-boot
has set up and be at 1GHz.

Does you SDK have omapconf? If yes

Please try

omapconf show opp

This should give us some clue.

Best Regards,
Keerthy

0 Shreek over 4 years ago in reply to Keerthy J

Intellectual 990 points

Keerthy,

I try "omapconf show opp" and got the following report:

omapconf: warning: no matching rate for VDD_DSPEVE OPP.Please check rates against Data Manual recommendations.
|-----------------------------------------------------------------------------------|
|                        | Temperature | Voltage | Frequency      | OPerating Point |
|-----------------------------------------------------------------------------------|
| VDD_CORE / VDD_CORE0   | 48C / 118F  | 0.000 V |                | NOM             |
|   L3                   |             |         |  266  MHz      |                 |
|   DMM                  |             |         |  266  MHz      |                 |
|   EMIF1                |             |         |  266  MHz      |                 |
|   EMIF2                |             |         |  266  MHz      |                 |
|     LP-DDR2            |             |         |  532  MHz      |                 |
|   L4                   |             |         |  266  MHz      |                 |
|   IPU1                 |             |         | (425  MHz) (1) |                 |
|     Cortex-M4 Cores    |             |         | (212  MHz) (1) |                 |
|   IPU2                 |             |         | (425  MHz) (1) |                 |
|     Cortex-M4 Cores    |             |         | (212  MHz) (1) |                 |
|   DSS                  |             |         | (192  MHz) (1) |                 |
|   BB2D                 |             |         | (354  MHz) (1) |                 |
|                        |             |         |                |                 |
| VDD_MPU / VDD_CORE1    | 51C / 123F  | 1.080 V |                | NOM             |
|   MPU (CPU1 ON)        |             |         |  1000 MHz      |                 |
|                        |             |         |                |                 |
| VDD_GPU / VDD_CORE2    | 50C / 122F  | 1.050 V |                | NOM             |
|   GPU                  |             |         | (425  MHz) (1) |                 |
|                        |             |         |                |                 |
| VDD_DSPEVE / VDD_CORE3 | 48C / 118F  | 1.010 V |                | UNKNOWN         |
|   DSP1                 |             |         | (600  MHz) (1) |                 |
|   DSP2                 |             |         | (600  MHz) (1) |                 |
|   EVE1                 |             |         | (0    MHz) (1) |                 |
|   EVE2                 |             |         | (0    MHz) (1) |                 |
|                        |             |         |                |                 |
| VDD_IVA / VDD_CORE4    | 50C / 122F  | 1.800 V |                | NOM             |
|   IVA                  |             |         | (388  MHz) (1) |                 |
|                        |             |         |                |                 |
|-----------------------------------------------------------------------------------|

Notes:
  (1) Module is disabled, rate may not be relevant.

/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor not found, no CPUFREQ?

omapconf: powerdm_deinit(): cpu not supported!!!
omapconf: clockdm_deinit(): cpu not supported!!!

It seems that the RT-Linux is running at 1GHz as configuration in uboot. So my issue is resoved.

By the way, how to modify the opp mode if OPP_OD or OPP_HIGH is required? I tried to set 'CONFIG_CPU_FREQ=y' and rebuild the RT-Linux kernel but failed to boot, So is there any other method?

0 Keerthy J over 4 years ago in reply to Shreek

TI__Guru**** 163100 points

Shreek,

You are not supposed to enable CPUFREQ on RT kernel as it very much defeats the RT nature. Once you
have cpufreq enabled then you can no longer have real time behavior. If you want cpufreq why don't you use
non-RT?

You may need for configs. Do a diff or RT Vs Non-RT Confg diff and you will need more configs to be enabled.

Please resolve the issue as your original issue of MPU at 1GHz is resolved.

Best Regards,
Keerthy

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AM5728: How to modify cpu freq for Linux-RT