j721s2-evm login:
j721s2-evm login: root
root@j721s2-evm:~# uname -a
Linux j721s2-evm 5.10.153-g90c3a58fd2 #1 SMP PREEMPT Fri Dec 16 07:50:16 UTC 2022 aarch64 aarch64 aarch64 GNU/Linux
root@j721s2-evm:~# ls
1323.test  1323.test.zip
root@j721s2-evm:~# cd 1323.test/
root@j721s2-evm:~/1323.test# ls
test.out
root@j721s2-evm:~/1323.test# chmod +x test.out
root@j721s2-evm:~/1323.test# ./test.out
======================cost:10007115===========
root@j721s2-evm:~/1323.test# k3conf dump clocks | grep -i a72
|     4     |     0    | DEV_A72SS0_ARM_CLK_CLK                                                            | CLK_STATE_READY     | 2000000000      |
|     4     |     1    | DEV_A72SS0_MSMC_CLK                                                               | CLK_STATE_READY     | 1000000000      |
|     4     |     2    | DEV_A72SS0_PLL_CTRL_CLK                                                           | CLK_STATE_READY     | 500000000       |
|     4     |     6    | DEV_A72SS0_A72_DIVH_CLK8_OBSCLK_OUT_CLK                                           | CLK_STATE_READY     | 0               |
|   202     |     0    | DEV_A72SS0_CORE0_ARM_CLK_CLK                                                      | CLK_STATE_READY     | 2000000000      |
|   203     |     0    | DEV_A72SS0_CORE1_ARM_CLK_CLK                                                      | CLK_STATE_READY     | 2000000000      |
root@j721s2-evm:~/1323.test# k3conf set clock 4 0 1200000000
|--------------------------------------------------------------------------------|
| VERSION INFO                                                                   |
|--------------------------------------------------------------------------------|
| K3CONF | (version v0.1-64-g48cb8e8 built Fri Dec 16 08:33:21 UTC 2022)         |
| SoC    | J721S2 SR1.0                                                          |
| SYSFW  | ABI: 3.1 (firmware version 0x0008 '8.5.2--v08.05.02 (Chill Capybar)') |
|--------------------------------------------------------------------------------|

|----------------------------------------------------------------------------------------------------|
| Device ID | Clock ID | Clock Name                              | Status          | Clock Frequency |
|----------------------------------------------------------------------------------------------------|
|     4     |     0    | DEV_A72SS0_ARM_CLK_CLK                  | CLK_STATE_READY | 1200000000      |
|     4     |     1    | DEV_A72SS0_MSMC_CLK                     | CLK_STATE_READY | 1000000000      |
|     4     |     2    | DEV_A72SS0_PLL_CTRL_CLK                 | CLK_STATE_READY | 500000000       |
|     4     |     6    | DEV_A72SS0_A72_DIVH_CLK8_OBSCLK_OUT_CLK | CLK_STATE_READY | 0               |
|----------------------------------------------------------------------------------------------------|

root@j721s2-evm:~/1323.test# ./test.out
======================cost:8338646===========
root@j721s2-evm:~/1323.test# devmem2 0x688040 w 0x80000001
/dev/mem opened.
Memory mapped at address 0xffffbbe98000.
Read at address  0x00688040 (0xffffbbe98040): 0x80000000
Write at address 0x00688040 (0xffffbbe98040): 0x80000001, readback 0x80000001
root@j721s2-evm:~/1323.test#
root@j721s2-evm:~/1323.test# devmem2 0x688040
/dev/mem opened.
Memory mapped at address 0xffff8b906000.
Read at address  0x00688040 (0xffff8b906040): 0x80000001
root@j721s2-evm:~/1323.test# ./test.out
[  131.700441] Initializing XFRM netlink socket
[  133.427973] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[  133.447160] Bridge firewalling registered
[  134.263686] process 'docker/tmp/qemu-check408115674/check' started with executable stack
======================cost:16843217===========
root@j721s2-evm:~/1323.test# k3conf set clock 4 0 2000000000
|--------------------------------------------------------------------------------|
| VERSION INFO                                                                   |
|--------------------------------------------------------------------------------|
| K3CONF | (version v0.1-64-g48cb8e8 built Fri Dec 16 08:33:21 UTC 2022)         |
| SoC    | J721S2 SR1.0                                                          |
| SYSFW  | ABI: 3.1 (firmware version 0x0008 '8.5.2--v08.05.02 (Chill Capybar)') |
|--------------------------------------------------------------------------------|

|----------------------------------------------------------------------------------------------------|
| Device ID | Clock ID | Clock Name                              | Status          | Clock Frequency |
|----------------------------------------------------------------------------------------------------|
|     4     |     0    | DEV_A72SS0_ARM_CLK_CLK                  | CLK_STATE_READY | 2000000000      |
|     4     |     1    | DEV_A72SS0_MSMC_CLK                     | CLK_STATE_READY | 1000000000      |
|     4     |     2    | DEV_A72SS0_PLL_CTRL_CLK                 | CLK_STATE_READY | 500000000       |
|     4     |     6    | DEV_A72SS0_A72_DIVH_CLK8_OBSCLK_OUT_CLK | CLK_STATE_READY | 0               |
|----------------------------------------------------------------------------------------------------|

root@j721s2-evm:~/1323.test# ./test.out
======================cost:10009196===========
root@j721s2-evm:~/1323.test# devmem2 0x688040
/dev/mem opened.
Memory mapped at address 0xffff9b3c9000.
Read at address  0x00688040 (0xffff9b3c9040): 0x80000001
root@j721s2-evm:~/1323.test#