AM5728 Max Frequency Change

ayusman

Intellectual 745 points

Other Parts Discussed in Thread: AM5728

Hi All,

The AM5728 works at 3 operating points with maximum frequency of 1.5GHz at OPP_HIGH.

I would like to know how I can set the frequency to 1.3GHz at OPP_HIGH.

Can anyone please help me out with this.

Regards

Ayusman

over 9 years ago

0 Yordan Kovachev over 9 years ago

TI__Guru**** 161600 points

Hi Ayusman,

Have you tried changing the omap_opp_def dra7xx_es1_0_opp_list[] __initdata structucture in arch/arm/mach-omap2/opp7xx_data.c:
/*
* We only include OPP_OD and OPP_HIGH here, OPP_NOM is common to all
* variants and left to be supplied by DT.
*/
static struct omap_opp_def dra7xx_es1_0_opp_list[] __initdata = {
/* MPU OPP - OPP_OD */
OPP_INITIALIZER("mpu", false, 1176000000, 1160000),
/* MPU OPP - OPP_HIGH */
OPP_INITIALIZER("mpu", false, 1500000000, 1210000),
};

OPP_NOM is defined in dra74x.dtsi:
operating-points = <
/* kHz uV */
1000000 1060000
>;

Best Regards,
Yordan

0 ayusman over 9 years ago in reply to Yordan Kovachev

Intellectual 745 points

Hi Yordan,

Thanks. We will try this out and let you know.
Also I see that we need to pass the clock frequency and the voltage as parameters. I would like to know what procedure should i follow to derive the required voltage for any given clock frequency.

Regards
Ayusman

0 Yordan Kovachev over 9 years ago in reply to ayusman

TI__Guru**** 161600 points

Hi Ayusman,

Follow the recommendations in AM572x DM, Table 5-7. Voltage Domains Operating Performance Points. The table describes MPU_VD voltage levels for the corresponding OPP.

Best Regards,
Yordan

0 ayusman over 9 years ago in reply to Yordan Kovachev

Intellectual 745 points

Hi Yordan,

I have gone through the table. However what I am looking for is the voltage to frequency relationship which I can use to set the register as shown in the code snippet shared by you.

My requirement is to set the OPP_HIGH at a lower clock frequency than 1.5GHz. For example, if I want to set it to 1.35GHz can you please let me know what will be the corresponding voltage ?

Regards
Ayusman

0 ayusman over 9 years ago in reply to ayusman

Intellectual 745 points

Hi Yordan,

Did you get a chance to go through my previous message.

Regards
Ayusman

0 Yordan Kovachev over 9 years ago in reply to ayusman

TI__Guru**** 161600 points

Hi,

For the MPU, it is stated that in OPP_HIGH, the voltage should be equal to the AVS voltage.
So you can set frequency to 1.35 & whatever voltage you like in the rage of 0.95 V - 1.25 V (AVS voltage for VD_MPU).
I recommend to change only the frequency to 1.35GHz & keep the default kernel setting for the voltage (1.21 V, as defined in omap_opp_def dra7xx_es1_0_opp_list).

Best Regards,
Yordan

0 ayusman over 9 years ago in reply to Yordan Kovachev

Intellectual 745 points

Hi,

I tried with the changes suggested but it didnot work. When I set the frequency to 1.35Ghz it always sets to 1.176Ghz. Do you have any idea why this doesnot work?

Regards
Ayusman

0 Yordan Kovachev over 9 years ago in reply to ayusman

TI__Guru**** 161600 points

Hi Ayusman,

I'll test it on my AM57xx GP EVM & post the feedback.
Have you changed anything else in the kernel sources?

Best Regards,
Yordan

0 Yordan Kovachev over 9 years ago in reply to Yordan Kovachev

TI__Guru**** 161600 points

Hi,

This is because you probably didn't change the following part of opp7xx_data.c:

case EFUSE_HAS_HIGH_MPU_OPP:

opp_def_list_enable_opp(dra7xx_es1_0_opp_list,

ARRAY_SIZE(dra7xx_es1_0_opp_list),

"mpu", 1500000000, true);

case EFUSE_HAS_HIGH_MPU_OPP:

opp_def_list_enable_opp(dra7xx_es1_0_opp_list,

ARRAY_SIZE(dra7xx_es1_0_opp_list),

"mpu", 1350000000, true);

After this modification, I booted my AM57xx GP EVM and executed bellow commands:

root@am57xx-evm:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

1000000

root@am57xx-evm:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors

conservative userspace powersave ondemand performance

root@am57xx-evm:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

ondemand

As you can see by default the CPU works on 1GHz. However I can see all my frequency definitions done in opp7xx_data.c:

root@am57xx-evm:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies

1000000 1176000 1350000

And I am able to change the frequency, once I pass the control to userspace governor:

root@am57xx-evm:~# echo userspace > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

root@am57xx-evm:~# echo 1350000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

root@am57xx-evm:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
1350000

So, as you can see, the following changes:

static struct omap_opp_def dra7xx_es1_0_opp_list[] __initdata = {
/* MPU OPP - OPP_OD */
OPP_INITIALIZER("mpu", false, 1176000000, 1160000),
/* MPU OPP - OPP_HIGH */
/*OPP_INITIALIZER("mpu", false, 1500000000, 1210000),*/
OPP_INITIALIZER("mpu", false, 1350000000, 1210000),
};

case EFUSE_HAS_HIGH_MPU_OPP:
opp_def_list_enable_opp(dra7xx_es1_0_opp_list,
ARRAY_SIZE(dra7xx_es1_0_opp_list),
"mpu", 1350000000, true);

Are enough to change OPP_HIGH to 1.35GHz

Best Regards,
Yordan

0 ayusman over 9 years ago in reply to Yordan Kovachev

Intellectual 745 points

Hi Yordan,

Thanks, I will test with these changes and get back to you in case I need any help.

Regards
Ayusman

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AM5728 Max Frequency Change