The RTT overflow callback is not available on all RTT implementations.
This means it is either a no-op or `rtt_set_overflow_cb()` is a no-op
or it will overwrite the alarm set with `rtt_set_alarm()`.
This adds a feature to indicate that proper overflow reporting is available.
Some periph_rtt implementations do not provide `rtt_set_counter()`. This
adds `periph_rtt_set_counter` as feature to allow testing for its
availability. The feature is provided at CPU level if periph_rtt is
provided by the board for all CPUs implementing `rtt_set_counter()`.
Some periph_rtt implementations do not provide `rtt_set_counter()`. This
adds `periph_rtt_set_counter` as feature to allow testing for its
availability. The feature is provided at CPU level if periph_rtt is
provided by the board for all CPUs implementing `rtt_set_counter()`.
The mv instruction (which is usually implemented as `add rd, x0, r1`) is
changed to `add rd, x0, %input`. This can either be used as a load
immediate or as an move.
The code size grows by two bytes. This because GCC does not compress the
li instruction to the compressed version (even though this is possible).
The RISC-V toolchain in riotdocker has issues with picolibc and
will still include newlib headers.
This leads to conflicts like
```
In file included from [01m[Knanostubs.c:22[m[K:
[01m[K/usr/local/picolibc/riscv-none-embed/include/stdio.h:270:23:[m[K [01;31m[Kerror: [m[Kconflicting types for '[01m[K__FILE[m[K'
typedef struct __file [01;31m[K__FILE[m[K;
[01;31m[K^~~~~~[m[K
In file included from [01m[K/opt/gnu-mcu-eclipse/riscv-none-gcc/8.2.0-2.2-20190521-0004/riscv-none-embed/include/reent.h:93[m[K,
from [01m[Knanostubs.c:20[m[K:
[01m[K/opt/gnu-mcu-eclipse/riscv-none-gcc/8.2.0-2.2-20190521-0004/riscv-none-embed/include/sys/reent.h:287:26:[m[K [01;36m[Knote: [m[Kprevious declaration of '[01m[K__FILE[m[K' was here
typedef struct __sFILE [01;36m[K__FILE[m[K;
[01;36m[K^~~~~~[m[K
```
The problem does not occur when installing both the toolchain and picolibc
directly from the Debian / Ubuntu repositories, but CI uses an older Ubuntu
version that does not have those packages yet, so it builds them manually.
Blacklist RISC-V until CI has been updated.
The RTC on the fe310 is emulated using the RTT.
This only works if the RTT frequency is 1 Hz, so default to that
value in case `periph_rtc` is selected.
Use RTC helper functions instead of libc functions.
This gives us y2038 safety by the extended epoch and saves
a good chunk of memory:
picolibc mktime():
text data bss dec hex filename
15048 520 2504 18072 4698 tests/periph_rtc/bin/hifive1/tests_periph_rtc.elf
rtc_mktime():
text data bss dec hex filename
7632 40 2452 10124 278c tests/periph_rtc/bin/hifive1/tests_periph_rtc.elf
