Re: [PATCH] [RFC] clk: stm32mp1: Keep RNG1 clock always running

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On 5/15/24 11:16 AM, Gatien CHEVALLIER wrote:

Hi,

What if you add a trace in a random generation function in random.c?

Do you have a function name or line number for me ?

I put a trace in _get_random_bytes() in drivers/char/random.c. I'm not
100% sure but this should be the entry point when getting a random number.

You're right, there is a read attempt right before the hang, and __clk_is_enabled() returns 0 in stm32_read_rng() . In fact, it is the pm_runtime_get_sync() which is returning -EACCES instead of zero, and this is currently not checked so the failure is not detected before register access takes place, to register file with clock disabled, which triggers a hard hang.

I'll be sending a patch shortly, thanks for this hint !

After this, I'll try to reproduce the issue.

If you have a minute to test it on some ST MP15 board, that would be real nice. Thanks !

I tried to reproduce the issue you're facing on a STM32MP157C-DK2 no
SCMI on the 6.9-rc7 kernel tag. I uses OP-TEE and TF-A in the bootchain
but this should not have an impact here.

How did you manage to test using "echo core > /sys/power/pm_test"?
In kernel/power/suspend.c, enter_state(). If the pm_test_level is core,
then an error is fired with the following trace:
"Unsupported test mode for suspend to idle, please choose none/freezer/devices/platform."

Could this be firmware related ?

I've tried using "echo devices > /sys/power/pm_test" so that I can at least test that the driver is put to sleep then wakes up. I do not
reproduce your issue.

Can you try 'processors' ?

I did also notice it sometimes takes much longer than a minute to hang, but eventually it does hang. Maybe let it cycle for an hour or a few ?

[...]

--
Best regards,
Marek Vasut




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