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STM32 : Add default deep sleep latency of 3ms #8798

Merged
merged 1 commit into from
Nov 30, 2018
Merged

STM32 : Add default deep sleep latency of 3ms #8798

merged 1 commit into from
Nov 30, 2018

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jeromecoutant
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@jeromecoutant jeromecoutant commented Nov 19, 2018 •
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Description

Feature has been introduced in #8223
Discussion on ST impacts started there: #8223 (comment)

@c1728p9 @LMESTM

Here is some quick measurement between the end of deep sleep (CPU) and the end of hal_deepsleep function:

  • NUCLEO_F401 : 824 us
  • NUCLEO_L476 : 2.04 ms
  • NUCLEO_L073 : 1.02 ms

So we propose to set as default value a deep sleep latency of 2ms.

Value can be overwritten in your target anyway:

"overrides": { "deep-sleep-latency": 5 },
or "overrides": { "deep-sleep-latency": 0 },

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

@0xc0170 0xc0170 requested review from c1728p9 and a team November 19, 2018 13:37
@0xc0170
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0xc0170 commented Nov 19, 2018

Q: 2s or 2ms? Reading the code , I believe it is milliseconds

@jeromecoutant jeromecoutant changed the title STM32 : Add default deep sleep latency of 2s STM32 : Add default deep sleep latency of 2ms Nov 19, 2018
@jeromecoutant
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Update done 😕

@mattbrown015
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@jeromecoutant How did you make your measurements?

I'd like to repeat your tests on my STM32L442. :-)

@jeromecoutant
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I set a GPIO to 1 at STOP mode exit and
0 at at the end of hal_deepsleep() in order to measure with a probe.

@mattbrown015
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@jeromecoutant

I set a GPIO to 1 at STOP mode exit and
0 at at the end of hal_deepsleep() in order to measure with a probe.

Pretty simple! I can give that a go. :-)

@mattbrown015
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@jeromecoutant The STM32L442 appears to be practically the same as the L476.

I measured 2.25 ms but assume the extra 0.2 ms is not a surprise or a concern. :-)

@LMESTM
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LMESTM commented Nov 22, 2018

@mattbrown015 interesting anyhow :-)
I think it's best to be pessimistic in the wake-up time.
If the core OS knows that something needs to be scheduled in 2.5ms, then better to avoid entering it ...
the energy spent in entering the mode and exiting immediately might even be more than what we save.
So I'd even make it up to 3ms and avoid side effects.

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LMESTM commented Nov 27, 2018

@jeromecoutant maybe change the PR title to 3ms before it gets merged ?

@jeromecoutant jeromecoutant changed the title STM32 : Add default deep sleep latency of 2ms STM32 : Add default deep sleep latency of 3ms Nov 27, 2018
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0xc0170 commented Nov 30, 2018

CI started

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mbed-ci commented Nov 30, 2018

Test run: SUCCESS

Summary: 4 of 4 test jobs passed
Build number : 1
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@cmonr cmonr merged commit 0b6ce4b into ARMmbed:master Nov 30, 2018
@jeromecoutant jeromecoutant deleted the PR_LATENCY branch January 17, 2019 12:51
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@LMESTM LMESTM LMESTM approved these changes

@0xc0170 0xc0170 0xc0170 approved these changes

@c1728p9 c1728p9 c1728p9 approved these changes

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@jeromecoutant @0xc0170 @mattbrown015 @LMESTM @mbed-ci @c1728p9 @cmonr