The API was based on the assumption that GPIO ports are mapped in memory
sanely, so that a `GPIO_PORT(num)` macro would work allow for constant
folding when `num` is known and still be efficient when it is not.
Some MCUs, however, will need a look up tables to efficiently translate
GPIO port numbers to the port's base address. This will prevent the use
of such a `GPIO_PORT(num)` macro in constant initializers.
As a result, we rather provide `GPIO_PORT_0`, `GPIO_PORT_1`, etc. macros
for each GPIO port present (regardless of MCU naming scheme), as well as
`GPIO_PORT_A`, `GPIO_PORT_B`, etc. macros if (and only if) the MCU port
naming scheme uses letters rather than numbers.
These can be defined as macros to the peripheral base address even when
those are randomly mapped into the address space. In addition, a C
function `gpio_port()` replaces the role of the `GPIO_PORT()` and
`gpio_port_num()` the `GPIO_PORT_NUM()` macro. Those functions will
still be implemented as efficient as possible and will allow constant
folding where it was formerly possible. Hence, there is no downside for
MCUs with sane peripheral memory mapping, but it is highly beneficial
for the crazy ones.
There are also two benefits for the non-crazy MCUs:
1. We can now test for valid port numbers with `#ifdef GPIO_PORT_<NUM>`
- This directly benefits the test in `tests/periph/gpio_ll`, which
can now provide a valid GPIO port for each and every board
- Writing to invalid memory mapped I/O addresses was treated as
triggering undefined behavior by the compiler and used as a
optimization opportunity
2. We can now detect at compile time if the naming scheme of the MCU
uses letters or numbers, and produce more user friendly output.
- This is directly applied in the test app
The EFM32 MCU allows the reference voltage to be configured per DAC device, not per DAC channel. Also, the DAC reference voltage was defined in the configuration but not used anywhere.
Since the USB OTG FIFO sizes are partly defined in 32-bit words and partly in bytes, the documentation of the of the USB OTG FIFO size definitions is extended by the respective unit.
`cpu/cortexm_common/include/cpu.h` has to be included in `cpu/efm32/periph_cpu.h` so that `PROVIDES_PM_SET_LOWEST` is defined if only `periph_cpu.h` is included. Otherwise `pm_set_lowest` is defined multiple times if the `pm_layered` module is not used. `PROVIDES_PM_OFF` has to be defined in case `pm_layered` is not used, e.g. in riotboot.
The EFM32 uses the provided _SILICON_LABS_32B_SERIES_0 and
_SILICON_LABS_32B_SERIES_1 definitions to enable or disable certain
code. With the introduction of new MCUs, there is also the
_SILICON_LABS_32B_SERIES_2 definition.
This PR ensures that the defines are explicit, and that #else
statements don't target the wrong series.
