[GitHub] haukepetersen opened a new pull request #231: hal/timer: do not assing ISR prio building for RIOT

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haukepetersen opened a new pull request #231: hal/timer: do not assing ISR prio building for RIOT
URL: https://github.com/apache/mynewt-nimble/pull/231
 
 
   I was recently debugging an issue running NimBLE in `observer` mode on top of RIOT (using a `nrf52dk`): every time triggering `ble_gap_disc()`, the application would hard-fault.
   
   It turned out, that this was caused to contradicting ISR priorities expected by RIOT and assigned by NimBLE (thanks to @andrzej-kaczmarek for pinpointing this). RIOT only uses a single, constant (`2`) interrupt priority for every ISR on Cortex-M platforms, but NimBLE is assigning the lowest possible priority to the `rtc` ISR. This leads to the `PendSV` ISR interrupting the rtc ISR, consequently leading to an invalid return value (`0xFFFFFFFD`) instead of (`0xFFFFFFF1`) read from the stack.
   
   So as an (possible intermediate) fix, I propose not to touch interrupt priorities when building for RIOT.
   
   Additional note: RIOT initializes the priority of every available vector to the mentioned constant value at boot time.

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