soc: stm32u0: add PM

[mickael868]

AFAIK, the stm32u0 target does not support the Power Management (PM) for now.

This PR copies the PM code from the STM32U5 target with few adaptation (eg. LL_PWR_STOP0_MODE -> LL_PWR_MODE_STOP0).

• Test 0 without this PR : 2mA

• Test 1: no peripheral enabled, no way to wake up after entering the stop1 mode: 3µA with the following overlay:

  cpus {
    cpu0: cpu@0 {
      cpu-power-states = <&stop0 &stop1>;
    };

    stop0: state0 {
      compatible = "zephyr,power-state";
      power-state-name = "suspend-to-idle";
      substate-id = <1>;
      min-residency-us = <100>;
    };
    stop1: state1 {
      compatible = "zephyr,power-state";
      power-state-name = "suspend-to-idle";
      substate-id = <2>;
      min-residency-us = <500>;
    };
  };

• Test 2: lptim2 (already not disabled in the dts/arm/st/u0/stm32u0.dtsi file) is used for a periodic wake up: 140µA with the following additional overlay:

stm32_lp_tick_source: &lptim2 {
  clocks = <&rcc STM32_CLOCK(APB1, 30U)>,
           <&rcc STM32_SRC_LSI LPTIM2_SEL(1)>;
  // st,prescaler = <8>; //doe not reduce power consumption
  status = "okay";
};

In both cases, it is necessary to disable the pm_policy_state_lock_get() calls from drivers/serial/uart_stm32.c because it takes the lock once at the first printk() call and never put it. This is the get backtrace if the banner is enabled:

Breakpoint 1, uart_poll_out (dev=<optimized out>, out_char=42 '*') at app/build/zephyr/include/generated/zephyr/syscalls/uart.h:108
108             z_impl_uart_poll_out(dev, out_char);
(gdb) backtrace
#0  uart_poll_out (dev=<optimized out>, out_char=42 '*') at app/build/zephyr/include/generated/zephyr/syscalls/uart.h:108
#1  console_out (c=42) at app/zephyr/drivers/console/uart_console.c:102
#2  0x080004a4 in char_out (c=<optimized out>, ctx_p=<optimized out>) at app/zephyr/lib/os/printk.c:98
#3  0x08004216 in vfprintf ()
#4  0x080004de in vprintk (fmt=0x8007689 "*** Booting Zephyr OS build v4.1.0-2646-ge41909a32ce9 ***\n", fmt@entry=0x1 <error: Cannot access memory at address 0x1>, ap=..., ap@entry=...) at app/zephyr/lib/os/printk.c:134
#5  0x0800560c in printk (fmt=0x8007689 "*** Booting Zephyr OS build v4.1.0-2646-ge41909a32ce9 ***\n") at app/zephyr/lib/os/printk.c:198
#6  0x08003ff0 in boot_banner () at app/zephyr/kernel/banner.c:46
#7  0x08002cc0 in bg_thread_main (unused1=<optimized out>, unused2=<optimized out>, unused3=<optimized out>) at app/zephyr/kernel/init.c:551
#8  0x08000508 in z_thread_entry (entry=0x8002cad <bg_thread_main>, p1=0x0, p2=0x0, p3=0x0) at app/zephyr/lib/os/thread_entry.c:48
#9  0x0800108c in arch_switch_to_main_thread (main_thread=0x8002cad <bg_thread_main>, stack_ptr=0x0, _main=0x8002cad <bg_thread_main>) at /home/mika/dev/embedded/zephyr/common/zephyr/arch/arm/core/cortex_m/thread.c:546
#10 0x20000608 in z_idle_threads ()

uart_stm32_pm_policy_state_lock_put_unconditional is never called. Tested with CONFIG_UART_INTERRUPT_DRIVEN=y.

I'm quiet new to Zephyr, does the UART issue comes an error I made?
Also, I think we should expect a lower power consumption when the LPTIM2 timer is used, do you have any idea how to improve this using only internal clocks? I will try to add a LSE oscillator in the next design (mainly for the LPUARTx peripherals) but I can not test it for now.

Thanks.

[github-actions]

Hello @mickael868, and thank you very much for your first pull request to the Zephyr project!
Our Continuous Integration pipeline will execute a series of checks on your Pull Request commit messages and code, and you are expected to address any failures by updating the PR. Please take a look at our commit message guidelines to find out how to format your commit messages, and at our contribution workflow to understand how to update your Pull Request. If you haven't already, please make sure to review the project's Contributor Expectations and update (by amending and force-pushing the commits) your pull request if necessary.
If you are stuck or need help please join us on Discord and ask your question there. Additionally, you can escalate the review when applicable. 😊

[JarmouniA]

Should be called inside

zephyr/soc/st/stm32/stm32u0x/soc.c

Line 28 in c2c3f75

void soc_early_init_hook(void)

if CONFIG_PM=y.

[mathieuchopstm]

First surface-level look.

This also lacks power states definition in Device Tree (dts/arm/st/u0/stm32u0.dtsi - see other series for reference)

[github-actions]

The following west manifest projects have changed revision in this Pull Request:

Name	Old Revision	New Revision	Diff
tf-m-tests	zephyrproject-rtos/tf-m-tests@502ea90 (v3.7-branch)	zephyrproject-rtos/tf-m-tests@c712761 (main)	zephyrproject-rtos/[email protected]
trusted-firmware-m	zephyrproject-rtos/trusted-firmware-m@857f369	zephyrproject-rtos/trusted-firmware-m@e2288c1 (main)	zephyrproject-rtos/[email protected]

Additional metadata changed:

Name	URL	Submodules	West cmds	module.yml
trusted-firmware-m				✏

⛔ DNM label due to: 1 project with metadata changes

Note: This message is automatically posted and updated by the Manifest GitHub Action.

[mickael868]

Sorry, I made a mess with the git remotes and it resulted in external commits being incorporated here.
Should I close this PR and start again ?

[mathieuchopstm]

Sorry, I made a mess with the git remotes and it resulted in external commits being incorporated here. Should I close this PR and start again ?

You should be able to fix the branch by resetting the tree (e.g., git reset --hard b8d4a6aa592bfb79e723b2c7a8374b3439f220a8) and re-applying your commits via cherry-pick (git cherry-pick 28a55e61c1a34fe02f7f46cf5eae02e9fb9af482 b31046e86b0a3990ff96fcae5babc213a8933b03 112e4b51e9ef6ac40cc0529cbe02a79ec204d025 4341a2c1f2a9eeaeaf6d16f846b4f6f6f4696537 f5502937aad0ecf1e72ef26b3c4514e8c1d7a60f c5998dc3d7b0b87e20baee7e067dc57dc76146be 4cf36b18ef8c3287b83521306b04d3466f2a8919 ac0676a678cf1f495a34f6aee2fe2341590b1341), then force-pushing to the branch (git push --force-with-lease or possibly git push --force)... but if you prefer, close the PR and open a new one.

[mickael868]

Closing and reopening to start from a clean local repository.