sys/busy_wait: add busy wait helper #20241

benpicco · 2024-01-09T18:08:00Z

Contribution description

We often need to wait for a short period of time before timers are initialized, e.g. in board_init().

Instead of ad-hoc busy wait implementations, provide a common busy_wait() helper function (taken from msp430) and add a busy_wait_us() for a rough time approximation based on the CPU frequency.

Testing procedure

A new test application is provided in tests/sys/busy_wait that will measure the diversion from the usec timer:

samd20-xpro (Cortex M0+)

2024-01-09 18:34:38,799 # waiting for 10 µs…
2024-01-09 18:34:38,801 # took 29 µs (diff: 19 µs)
2024-01-09 18:34:38,803 # waiting for 100 µs…
2024-01-09 18:34:38,806 # took 119 µs (diff: 19 µs)
2024-01-09 18:34:38,808 # waiting for 1000 µs…
2024-01-09 18:34:38,812 # took 1012 µs (diff: 12 µs)
2024-01-09 18:34:38,814 # waiting for 10000 µs…
2024-01-09 18:34:38,827 # took 9942 µs (diff: -58 µs)

saml10-xpro (Cortex M23)

2024-01-09 19:06:53,208 # waiting for 10 µs…
2024-01-09 19:06:53,211 # took 38 µs (diff: 28 µs)
2024-01-09 19:06:53,213 # waiting for 100 µs…
2024-01-09 19:06:53,216 # took 128 µs (diff: 28 µs)
2024-01-09 19:06:53,218 # waiting for 1000 µs…
2024-01-09 19:06:53,222 # took 1029 µs (diff: 29 µs)
2024-01-09 19:06:53,224 # waiting for 10000 µs…
2024-01-09 19:06:53,237 # took 10028 µs (diff: 28 µs)

same54-xpro (Cortex M4F)

2024-01-09 19:07:30,669 # waiting for 10 µs…
2024-01-09 19:07:30,671 # took 14 µs (diff: 4 µs)
2024-01-09 19:07:30,673 # waiting for 100 µs…
2024-01-09 19:07:30,676 # took 103 µs (diff: 3 µs)
2024-01-09 19:07:30,678 # waiting for 1000 µs…
2024-01-09 19:07:30,681 # took 1003 µs (diff: 3 µs)
2024-01-09 19:07:30,683 # waiting for 10000 µs…
2024-01-09 19:07:30,696 # took 10003 µs (diff: 3 µs)

avr-rss2 (AVR8)

2024-01-09 23:07:08,152 # waiting for 10 µs…
2024-01-09 23:07:08,153 # took 96 µs (diff: 86 µs)
2024-01-09 23:07:08,153 # waiting for 100 µs…
2024-01-09 23:07:08,153 # took 208 µs (diff: 108 µs)
2024-01-09 23:07:08,154 # waiting for 1000 µs…
2024-01-09 23:07:08,154 # took 1104 µs (diff: 104 µs)
2024-01-09 23:07:08,155 # waiting for 10000 µs…
2024-01-09 23:07:08,155 # took 10112 µs (diff: 112 µs)

esp8266-esp-12x (ESP8266)

2024-01-09 23:19:50,829 # waiting for 10 µs…
2024-01-09 23:19:50,829 # took 20 µs (diff: 10 µs)
2024-01-09 23:19:50,830 # waiting for 100 µs…
2024-01-09 23:19:50,830 # took 106 µs (diff: 6 µs)
2024-01-09 23:19:50,830 # waiting for 1000 µs…
2024-01-09 23:19:50,831 # took 1007 µs (diff: 7 µs)
2024-01-09 23:19:50,831 # waiting for 10000 µs…
2024-01-09 23:19:50,832 # took 10007 µs (diff: 7 µs)

esp32-wroom-32 (ESP32)

2024-01-09 23:11:12,958 # waiting for 10 µs…
2024-01-09 23:11:12,959 # took 12 µs (diff: 2 µs)
2024-01-09 23:11:12,959 # waiting for 100 µs…
2024-01-09 23:11:12,960 # took 102 µs (diff: 2 µs)
2024-01-09 23:11:12,960 # waiting for 1000 µs…
2024-01-09 23:11:12,960 # took 1002 µs (diff: 2 µs)
2024-01-09 23:11:12,961 # waiting for 10000 µs…
2024-01-09 23:11:12,961 # took 10002 µs (diff: 2 µs)

esp32s2-wemos-mini (ESP32S2)

2024-01-09 23:30:08,115 # waiting for 10 µs…
2024-01-09 23:30:08,117 # took 20 µs (diff: 10 µs)
2024-01-09 23:30:08,119 # waiting for 100 µs…
2024-01-09 23:30:08,121 # took 151 µs (diff: 51 µs)
2024-01-09 23:30:08,123 # waiting for 1000 µs…
2024-01-09 23:30:08,127 # took 1010 µs (diff: 10 µs)
2024-01-09 23:30:08,129 # waiting for 10000 µs…
2024-01-09 23:30:08,142 # took 10010 µs (diff: 10 µs)

esp32s3-devkit (ESP32S3)

2024-01-09 23:23:44,314 # waiting for 10 µs…
2024-01-09 23:23:44,314 # took 13 µs (diff: 3 µs)
2024-01-09 23:23:44,315 # waiting for 100 µs…
2024-01-09 23:23:44,315 # took 103 µs (diff: 3 µs)
2024-01-09 23:23:44,315 # waiting for 1000 µs…
2024-01-09 23:23:44,316 # took 1002 µs (diff: 2 µs)
2024-01-09 23:23:44,316 # waiting for 10000 µs…
2024-01-09 23:23:44,317 # took 10003 µs (diff: 3 µs)

esp32c3-devkit (RISC-V)

2024-01-09 23:33:23,096 # waiting for 10 µs…
2024-01-09 23:33:23,097 # took 14 µs (diff: 4 µs)
2024-01-09 23:33:23,100 # waiting for 100 µs…
2024-01-09 23:33:23,102 # took 103 µs (diff: 3 µs)
2024-01-09 23:33:23,105 # waiting for 1000 µs…
2024-01-09 23:33:23,107 # took 1002 µs (diff: 2 µs)
2024-01-09 23:33:23,108 # waiting for 10000 µs…
2024-01-09 23:33:23,112 # took 10003 µs (diff: 3 µs)

sipeed-longan-nano (RISC-V)

2024-01-09 23:37:05,709 # waiting for 10 µs…
2024-01-09 23:37:05,709 # took 13 µs (diff: 3 µs)
2024-01-09 23:37:05,709 # waiting for 100 µs…
2024-01-09 23:37:05,710 # took 113 µs (diff: 13 µs)
2024-01-09 23:37:05,711 # waiting for 1000 µs…
2024-01-09 23:37:05,711 # took 1013 µs (diff: 13 µs)
2024-01-09 23:37:05,712 # waiting for 10000 µs…
2024-01-09 23:37:05,718 # took 10014 µs (diff: 14 µs)

Issues/PRs references

riot-ci · 2024-01-09T18:29:45Z

Murdock results

✔️ PASSED

9cf1c47 tests/sys/busy_wait: add test for busy wait

Success	Failures	Total	Runtime
8101	0	8101	11m:37s

Artifacts

Documentation preview

maribu

Nice one. The blinky example could also make use of this :-)

sys/include/busy_wait.h

cpu/avr8_common/include/cpu.h

tests/sys/busy_wait/main.c

sys/include/busy_wait.h

benpicco · 2024-01-11T12:20:05Z

@maribu if you run the test on MSP430 you can also provide CPU_CYCLES_PER_LOOP for it.

benpicco added 2 commits January 9, 2024 19:03

sys/busy_wait: add busy wait helper

bfd29f0

cpu/cortexm_common: Cortex M0/M23 needs 4 cycles/busy loop

79b51ef

benpicco requested review from leandrolanzieri, aabadie, MichelRottleuthner, kaspar030, gschorcht and bergzand as code owners January 9, 2024 18:08

benpicco requested review from maribu and removed request for aabadie, kaspar030, bergzand, leandrolanzieri, MichelRottleuthner and gschorcht January 9, 2024 18:08

github-actions bot added Platform: MSP Platform: This PR/issue effects MSP-based platforms Platform: ARM Platform: This PR/issue effects ARM-based platforms Area: tests Area: tests and testing framework Area: cpu Area: CPU/MCU ports Area: sys Area: System labels Jan 9, 2024

benpicco added the CI: ready for build If set, CI server will compile all applications for all available boards for the labeled PR label Jan 9, 2024

maribu approved these changes Jan 9, 2024

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benpicco requested review from kYc0o and nandojve as code owners January 9, 2024 22:08

github-actions bot added Platform: AVR Platform: This PR/issue effects AVR-based platforms Platform: ESP Platform: This PR/issue effects ESP-based platforms labels Jan 9, 2024

Teufelchen1 reviewed Jan 10, 2024

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cpu/avr8_common/include/cpu.h Show resolved Hide resolved

tests/sys/busy_wait/main.c Show resolved Hide resolved

kaspar030 reviewed Jan 10, 2024

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sys/include/busy_wait.h Show resolved Hide resolved

cpu/avr8_common: AVR-8 needs 7 cycles per busy loop

5dc43bd

benpicco added 2 commits January 10, 2024 22:43

cpu/esp8266: ESP8266 needs 5 cycles per busy loop

8bcfe7b

cpu/esp32: add busy loop cycles for all sub-arches

fff9ff1

benpicco force-pushed the busy_wait branch from 77504bb to a043615 Compare January 10, 2024 21:43

benpicco added the CI: no fast fail don't abort PR build after first error label Jan 11, 2024

benpicco added this pull request to the merge queue Jan 11, 2024

github-merge-queue bot removed this pull request from the merge queue due to failed status checks Jan 11, 2024

tests/sys/busy_wait: add test for busy wait

9cf1c47

benpicco force-pushed the busy_wait branch from a043615 to 9cf1c47 Compare January 11, 2024 12:03

benpicco added this pull request to the merge queue Jan 11, 2024

Merged via the queue into RIOT-OS:master with commit 714958a Jan 11, 2024
25 checks passed

benpicco deleted the busy_wait branch January 11, 2024 15:26

MrKevinWeiss added this to the Release 2024.01 milestone Feb 7, 2024

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sys/busy_wait: add busy wait helper #20241

sys/busy_wait: add busy wait helper #20241

benpicco commented Jan 9, 2024 •

edited

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riot-ci commented Jan 9, 2024 •

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maribu left a comment

benpicco commented Jan 11, 2024

sys/busy_wait: add busy wait helper #20241

sys/busy_wait: add busy wait helper #20241

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benpicco commented Jan 9, 2024 • edited Loading

Contribution description

Testing procedure

samd20-xpro (Cortex M0+)

saml10-xpro (Cortex M23)

same54-xpro (Cortex M4F)

avr-rss2 (AVR8)

esp8266-esp-12x (ESP8266)

esp32-wroom-32 (ESP32)

esp32s2-wemos-mini (ESP32S2)

esp32s3-devkit (ESP32S3)

esp32c3-devkit (RISC-V)

sipeed-longan-nano (RISC-V)

Issues/PRs references

riot-ci commented Jan 9, 2024 • edited Loading

Murdock results

Artifacts

maribu left a comment

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benpicco commented Jan 11, 2024

benpicco commented Jan 9, 2024 •

edited

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riot-ci commented Jan 9, 2024 •

edited

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