UBLOX_C030_U201: tests-mbed_drivers-lp_timer failing nightly

[0xc0170]

Description

IAR and GCC ARM affected at least. At least two latest nightly run

[1559265072.39][CONN][RXD] >>> Running case #2: 'Test: LowPowerTimer - measure time accumulation.'...
[1559265072.39][CONN][INF] found KV pair in stream: {{__testcase_start;Test: LowPowerTimer - measure time accumulation.}}, queued...
mbedgt: :123::FAIL: Expected 0.010000 Was 0.011125
[1559265072.49][CONN][RXD] :123::FAIL: Expected 0.010000 Was 0.011125
[1559265072.60][CONN][INF] found KV pair in stream: {{__testcase_finish;Test: LowPowerTimer - measure time accumulation.;0;1}}, queued...
[1559265072.69][CONN][RXD] >>> 'Test: LowPowerTimer - measure time accumulation.': 0 passed, 1 failed with reason 'Assertion Failed'
[1559265072.69][CONN][RXD]
[1559265072.79][CONN][RXD] >>> Test cases: 1 passed, 1 failed with reason 'Assertion Failed'
[1559265072.79][CONN][RXD] >>> TESTS FAILED!

The full report:

| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - float operator.                                                             | 0      | 0      | SKIPPED | 0.0                |
| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - measure time accumulation.                                                  | 0      | 1      | FAIL    | 0.1                |
| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - reset.                                                                      | 0      | 0      | SKIPPED | 0.0                |
| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - start started timer.                                                        | 0      | 0      | SKIPPED | 0.0                |
| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - stopped after creation.                                                     | 1      | 0      | OK      | 0.09               |
| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - time measurement 1 ms.                                                      | 0      | 0      | SKIPPED | 0.0                |
| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - time measurement 1 s.                                                       | 0      | 0      | SKIPPED | 0.0                |
| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - time measurement 10 ms.                                                     | 0      | 0      | SKIPPED | 0.0                |
| UBLOX_C030_U201-IAR | UBLOX_C030_U201 | tests-mbed_drivers-lp_timer                                                  | Test: LowPowerTimer - time measurement 100 ms.                                                    | 0      | 0      | SKIPPED | 0.0                |

Full report can be found http://mbed-os-ci.s3-website-eu-west-1.amazonaws.com/?prefix=jenkins-ci/ARMmbed/mbed-os/mbed-os-ci-nightly/artifacts/master/224/greentea-test-HAL-Core/78/FAIL/UBLOX_C030_U201/

cc @ARMmbed/team-ublox @MarceloSalazar

Issue request type

[ ] Question
[ ] Enhancement
[X] Bug

[fahimalavi]

I haven't seen this problem with C030-U201 in our local automation system. But we will check your logs and update you. Internal JIRA ticket for reference PGM_NO_MBD-238

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-1242

[mudassar-ublox]

Issue didn't reproduced with us. Attaching logs.

C030_U201_Test_Logs.txt

[mprse]

UBLOX_C030_U201 has STM32F437VG76 MCU. This MCU does not have LPTIM peripheral and low power timer is driven by RTC (LSI):

mbed-os/targets/TARGET_STM/lp_ticker.c

Lines 512 to 519 in 8fb43a8

	const ticker_info_t *lp_ticker_get_info()
	{
	static const ticker_info_t info = {
	RTC_CLOCK / 4, // RTC_WAKEUPCLOCK_RTCCLK_DIV4
	32
	};
	return &info;
	}

mbed-os/targets/TARGET_STM/rtc_api_hal.h

Lines 41 to 45 in 8fb43a8

	#if MBED_CONF_TARGET_LSE_AVAILABLE
	#define RTC_CLOCK LSE_VALUE
	#else
	#define RTC_CLOCK LSI_VALUE
	#endif

According to the documentation of STM32F437VG76 MCU:

The LSI RC acts as an low-power clock source that can be kept running in Stop and
Standby mode for the independent watchdog (IWDG) and Auto-wakeup unit (AWU). The
clock frequency is around 32 kHz. For more details, refer to the electrical characteristics
section of the datasheets.

It seems that typical LSI frequency is 32 kHz, but it may vary from 17 to 47 kHz! This makes a huge difference and means that we can't rely on configured LSI frequency:

mbed-os/targets/TARGET_STM/TARGET_STM32F4/device/stm32f4xx_hal_conf.h

Lines 125 to 127 in 8fb43a8

	#if !defined (LSI_VALUE)
	#define LSI_VALUE 32000U /*!< LSI Typical Value in Hz */
	#endif /* LSI_VALUE */ /*!< Value of the Internal Low Speed oscillator in Hz

I have measured the real lp-ticker frequency on my local target (where the test passes) and on the nightly/RAAS target (where the test fails). The table below shows the number of lp-ticker ticks during 1 sec (lp-ticker frequency). The 1 sec time period was defined using the us-ticker.

Test	RAAS	LOCAL
1	8835	7951
2	8853	7953
3	8866	7971
4	8873	7973
5	8873	7966
6	8866	7965
7	8853	7970
8	8847	7966
9	8855	7971
10	8867	7974
11	8857	7971
12	8854	7976
13	8846	7972
14	8860	7974
15	8871	7973
16	8870	7976
17	8871	7980
18	8873	7978
19	8872	7977
20	8891	7974

	RAAS	LOCAL
Average	8863	7971

We can see that the frequency is not stable and we have different average lp-ticker frequencies on RAAS target (8.8 kHz) and my local target (7.9 kHz). This gives the following real LSI frequency:

• RAAS: 8863 Hz * 4 = 35 452 Hz
• LOCAL: 7971 Hz * 4 = 31 884‬ Hz

This explains why the test fails on RAAS target (configured LSI frequency is 32 000 Hz).

Got the following propositions:

1. Disable lp-ticker for STM targets that use LSI. According to the requirements, lp-ticker accuracy should be +/- 10%. Since the test is failing this requirement is not met.

2. Extend the ticker information structure with a field like calibration_required:
   

   mbed-os/hal/ticker_api.h

   Lines 53 to 56 in 8fb43a8

   	typedef struct {
   	uint32_t frequency; /**< Frequency in Hz this ticker runs at */
   	uint32_t bits; /**< Number of bits this ticker supports */
   	} ticker_info_t;

a) if calibration_required field is set to true then lp-ticker tests should be skipped - bad solution since in such case lp-ticker will not be tested.
b) provide some calibration mechanism that should be used before the test (if calibration_required field is set to true) - this might be tricky but makes sense to me.

Other ideas?
cc @jamesbeyond @0xc0170 @fahim-ublox @LMESTM @jeromecoutant

[MarceloSalazar]

LPtimer for F4x9 is disabled and not supported.