error: DWT implements no cycle counter. Cannot be used for cycle counting.

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

moose — Fri, 17 Dec 2021 19:40:48 GMT

I have updated my zephyr base to the latest version in main and I can confirm that the timing function works now. Thanks for your support.

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

davege — Fri, 10 Dec 2021 13:12:22 GMT

This is perfect!
Thanks Sigurd

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

Sigurd — Fri, 10 Dec 2021 13:07:47 GMT

PR was merged now.

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

Sigurd — Fri, 10 Dec 2021 10:18:10 GMT

Hi davege,

Sorry for the delay.

We have now opened a PR in upstream Zephyr.

https://github.com/zephyrproject-rtos/zephyr/pull/41057

[quote userid="90495" url="~/f/nordic-q-a/75041/error-dwt-implements-no-cycle-counter-cannot-be-used-for-cycle-counting/342718#342718"]do you know if this fix will be included in the next Zephyr version?[/quote]

Next Zephyr release is v3.0, planned for February next year, so the PR should most likely have been merged before that.

https://github.com/zephyrproject-rtos/zephyr/wiki/Program-Management#actual-and-planned-milestone-dates

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

davege — Thu, 09 Dec 2021 12:52:27 GMT

Sigurd do you know if this fix will be included in the next Zephyr version?

Any update would be welcome.

Thanks

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

Sigurd — Mon, 16 Aug 2021 15:26:35 GMT

Sure, I can post a link to the github PR here when it's created.

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

davege — Mon, 16 Aug 2021 15:23:19 GMT

Thanks for the follow up Sigurd.

Good to know it is just a minor bug in the code.

Could you keep us posted here on the resolution from the developers?

Thanks

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

Sigurd — Mon, 16 Aug 2021 15:05:56 GMT

Hi,

There was a bug in earlier NCS versions that made this ASSERT to be ignored(warning about this was printed in the build log).

It's now asserting in NCS v1.6.x.

It looks to be bug in Zephyr, and I have reported it to the developer.

In the code we have:
__ASSERT((DWT->CTRL & DWT_CTRL_NOCYCCNT_Msk) != 0,

It should be
__ASSERT((DWT->CTRL & DWT_CTRL_NOCYCCNT_Msk) == 0,

From ARMv7-M Architecture Reference Manual:
NOCYCCNT, bit[25] Shows whether the implementation supports a cycle counter:
0 Cycle counter supported.
1 Cycle counter not supported

From ARMv8-M Architecture Reference Manual:
NOCYCCNT, bit [25]
No cycle count. Indicates whether the implementation does not include a cycle counter.
The possible values of this bit are:
0 Cycle counter implemented.
1 Cycle counter not implemented.

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

moose — Tue, 27 Jul 2021 21:30:18 GMT

Any update on this? I am still experiencing the same issue. Thx!

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

davege — Mon, 26 Jul 2021 15:05:49 GMT

Hello,

I'm experiencing exactly the same problem using nrf52840 DK (PCA10056).

If I set CONFIG_TIMING_FUNCTIONS=y, by default the Timing Zephyr subsystem will pick the architecture-dependent implementation (arch_).

So, when invoking timing_init, this function in zephyr\arch\arm\include\aarch32\cortex_m\dwt.h will be invoked:

/**
 * @brief Initialize and Enable the DWT cycle counter
 *
 * This routine enables the cycle counter and initializes its value to zero.
 *
 * @return 0
 */
static inline int z_arm_dwt_init_cycle_counter(void)
{
	/* Clear and enable the cycle counter */
	DWT->CYCCNT = 0;
	DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;

	/* Assert that the cycle counter is indeed implemented. */
	__ASSERT((DWT->CTRL & DWT_CTRL_NOCYCCNT_Msk) != 0,
		"DWT implements no cycle counter. "
		"Cannot be used for cycle counting\n");

	return 0;
}

And contextually, the assert is triggered.

I think this is easily reproducible, I'm using a standard dev kit atm.
I don't have any other board to use with the same chip, but I don't see any reason why it would mean that this board is faulty...

Can anybody try to confirm this?
It maybe a timing issue in the asserting condition.

Note: I initially wondered why a benchmark sample (latency measure) was working fine measuring time with DWT. I then realised that asserts are just disabled in the sample...

...
CONFIG_FORCE_NO_ASSERT=y
...

Thanks in advance for your help!

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

Sigurd — Tue, 18 May 2021 07:59:11 GMT

Hi,

Here is my project, I used NCS v1.5.0, and I'm not able to re-create this when building for board nrf52833dk_nrf52833

devzone.nordicsemi.com/.../timing.zip

If you are not using nrf52833dk_nrf52833 , then it might be an issue with your board files.

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

moose — Fri, 14 May 2021 17:24:04 GMT

I already have this config statement in my proj.conf.

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

Sigurd — Fri, 14 May 2021 13:17:59 GMT

Hi,

Try setting this in prj.conf:

CONFIG_TIMING_FUNCTIONS=y

RE: error: DWT implements no cycle counter. Cannot be used for cycle counting.

moose — Thu, 13 May 2021 12:24:43 GMT

Any ideas?