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Posted to commits@mynewt.apache.org by GitBox <gi...@apache.org> on 2018/07/27 13:16:29 UTC
[GitHub] utzig edited a comment on issue #1299: [RFC] [NRF52] Remove
uint64_t div in watchdog init
utzig edited a comment on issue #1299: [RFC] [NRF52] Remove uint64_t div in watchdog init
URL: https://github.com/apache/mynewt-core/pull/1299#issuecomment-408415181
@mkiiskila @wes3 This is mostly a Proof of Concept, based on Marko's comments here: https://github.com/runtimeco/mcuboot/pull/322
Some numbers, based on mcuboot loader:
Without watchdog initialization linked in the size is `9660` bytes. With the current watchdog initialization it is `10568`. This amount is due to this code generated because of the `uint64_t` division:
```
/* Convert msec timeout to counts of a 32768 crystal */
expiration = ((uint64_t)expire_msecs * 32768) / 1000;
85c:»··f44f 727a »·mov.w»··r2, #1000»··; 0x3e8
860:»··2300 »·movs»···r3, #0
862:»··03c0 »·lsls»···r0, r0, #15
864:»··0c49 »·lsrs»···r1, r1, #17
866:»··f001 fdd9 »·bl»·241c <__aeabi_uldivmod>
NRF_WDT->CRV = (uint32_t)expiration;
```
With the updated code the size is `9860` bytes. I suppose the change would be less significant in a final firmware where `__aeabi_uldivmod` might be linked in anyway, so leaving this here for RFC only now!
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