AM3352: AM3352BZCEA30 is recommended to have frequency scaling functionality?

Harsh Patel35

Part Number: AM3352

Tool/software:

Hi TI Team,

With SDK 9.1, by default frequency scaling options is disabled for AM3352 and thus the processor works at fixed 300 Mhz.

For reference:
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
cat: can't open '/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies': No such file or directory

In past, tried to enable the frequency scaling with SDK 4.03 and able to get 150 and 75 options [with not recommended dts configs].

opp50@150000000 {
opp-hz = /bits/ 64 <150000000>;
opp-microvolt = <950000 931000 969000>;
opp-supported-hw = <0xFF 0xFFFF>;
opp-suspend;
};

I guess, opp-supported-hw value is not correct for AM3352.

Our previous discussion on this topic:
AM3352: Frequency scaling in AM3352BZCEA30 - Processors forum - Processors - TI E2E support forums

The short question is,
Does TI recommend using frequency scaling for chip AM3352BZCEA30?

If yes, then,
1. For which frequencies? [150, 75, or lower]

2. What will be the recommended dts config for the same?

Thanks in Advance

Regards,
Patel

10 months ago

0 Anshu Madwesh 10 months ago

TI__Mastermind 19235 points

Hi Patel,

SDK 9.1 should support CPUFREQ to adjusting the A8 core frequency.

Refer to the AM335x datasheet Table 5-9: https://www.ti.com/lit/ds/symlink/am3352.pdf

I will check internally to confirm that it could not go lower than 300MHz. Please expect a response by Monday next week.

Best Regards,
Anshu

0 Harsh Patel35 10 months ago in reply to Anshu Madwesh

Intellectual 330 points

Hi Anshu

Thanks for quick response.
Regarding your comment, "SDK 9.1 should support CPUFREQ to adjusting the A8 core frequency.",
Yes, it is.

Additionally, on main topic I can see some issues regarding OPP50 in AM3352 Errata [AM335x Sitara Processors Silicon Revisions 2.1, 2.0, 1.0 (Rev. I)] thus expecting the confirmation from TI on frequency scaling options.

Thanks again.

Regards,
Patel

0 Anshu Madwesh 10 months ago in reply to Harsh Patel35

TI__Mastermind 19235 points

Hi Patel,

Thank you for your patience. After discussing with the hardware team, it seems to be possible to run the AM335x device at 275MHz. We cannot suggest operating the A8 cortex any lower than 275MHz.

Best Regards,

Anshu

0 Harsh Patel35 10 months ago in reply to Anshu Madwesh

Intellectual 330 points

Hi Anshu,

Thank you for the response.

Before we close this thread,
1. Can I have the reason for not recommending below 275MHz?
2. Also, it would be great if we have patch available for AM3352 having 300 and 275 MHz.

Thanks.

0 Anshu Madwesh 10 months ago in reply to Harsh Patel35

TI__Mastermind 19235 points

Hi Patel,

Harsh Patel35 said:
1. Can I have the reason for not recommending below 275MHz?

I don't know for sure, but unlikely that TI has validated the A8 Cortex for functionality at any lower speed.

Harsh Patel35 said:
2. Also, it would be great if we have patch available for AM3352 having 300 and 275 MHz.

There is no patch available. You can refer to this commit for some more information: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/commit/arch/arm/boot/dts/am33xx.dtsi?h=ti-linux-6.1.y&id=72ac40fcb164a3d8fbd1ff13647abe67df26ced5

Thanks,

Anshu