How to view and modify the current CPU frequency of STM32MP157D

[zengyixiang]

Does anyone know how to view and modify the current CPU frequency of STM32MP157D? I also cannot use the following command:

root@stm32mp1:/sys# cat /proc/cpuinfo
processor       : 0
model name      : ARMv7 Processor rev 5 (v7l)
BogoMIPS        : 48.00
Features        : half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xc07
CPU revision    : 5

processor       : 1
model name      : ARMv7 Processor rev 5 (v7l)
BogoMIPS        : 48.00
Features        : half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xc07
CPU revision    : 5

Hardware        : STM32 (Device Tree Support)
Revision        : 0000
Serial          : 003C00403132510831323338
root@stm32mp1:/sys# cd /
root@stm32mp1:/# cat /proc/cpuinfo
processor       : 0
model name      : ARMv7 Processor rev 5 (v7l)
BogoMIPS        : 48.00
Features        : half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xc07
CPU revision    : 5

processor       : 1
model name      : ARMv7 Processor rev 5 (v7l)
BogoMIPS        : 48.00
Features        : half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xc07
CPU revision    : 5

Hardware        : STM32 (Device Tree Support)
Revision        : 0000
Serial          : 003C00403132510831323338

There is only BogoMIPS: 48 above, I want to know what to do with the current clock frequency of the CPU?

[Erwan SZYMANSKI]

Hello @zengyixiang ,
You can check the minimum, maximum and current CPU frequency in this folder :

Board $> cd /sys/devices/system/cpu/cpufreq/policy0/

You can check following parameters :

• cpuinfo_cur_freq
• cpuinfo_max_freq
• cpuinfo_min_freq

In the same folder, you have the scaling_governor that will manage the frequency changes. You can look online the documentation, but I think you can change it from schedutil to performance for example.

Kind regards,
Erwan.

[zengyixiang]

Hello, I have seen it, but it seems that my CPU frequency is limited to 800MHz, with both the maximum and minimum being 800MHz. I would like to lower the frequency. How can I modify the minimum CPU frequency.

# pwd
/sys/devices/system/cpu/cpufreq/policy0
# cat cpuinfo_max_freq
800000
# cat cpuinfo_min_freq
800000
# cat cpuinfo_cur_freq
800000
#

[Erwan SZYMANSKI]

Hello @zengyixiang ,
Is it a personal PCB design ? 

The different CPU frequency configuration are described in OP-TEE and Linux device trees, in OPP tables nodes (operating points). On the last SW revision (OpenSTLinux 5.1) it is in stm32mp151.dtsi .

You can see the following :

cpu0_opp_table: cpu0-opp-table {
		compatible = "operating-points-v2";
		opp-shared;

		opp-400000000 {
			opp-hz = /bits/ 64 <400000000>;
			opp-microvolt = <1200000>;
			opp-supported-hw = <0x2>;
			opp-suspend;
		};

		opp-650000000 {
			opp-hz = /bits/ 64 <650000000>;
			opp-microvolt = <1200000>;
			opp-supported-hw = <0x1>;
			st,opp-default;
		};

		opp-800000000 {
			opp-hz = /bits/ 64 <800000000>;
			opp-microvolt = <1350000>;
			opp-supported-hw = <0x2>;
			st,opp-default;
		};
	};

It seems strange that your minimum is 800 MHz as for your revision, the 2 default mode we provide is 650 / 800. Can you please check that you have these definitions too ?

You should also be able to see these nodes in Linux kernel device trees. Please check it too.

Kind regards,
Erwan.

[zengyixiang]

是的，我自己设计了 PCB，我的电源管理使用“EA3059QDR”芯片而不是“STPMIC1APQR”。我将VDDCORE固定在1.35V：

	vddcore: regulator-vddcore {
        compatible = "regulator-fixed";
		regulator-name = "vddcore";
		regulator-min-microvolt = <1350000>;
		regulator-max-microvolt = <1350000>;
		regulator-always-on;
        regulator-boot-on;
	};

&cpu0_opp_table {
		opp-800000000 {
			opp-hz = /bits/ 64 <800000000>;
			opp-microvolt = <1350000>;
			opp-supported-hw = <0x2>;
		};
		opp-400000000 {
			opp-hz = /bits/ 64 <400000000>;
			opp-microvolt = <1200000>;
			opp-supported-hw = <0x2>;
			opp-suspend;
		};
};