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drivers/periph_gpio_ll: change API to access GPIO ports #20639

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drivers/periph_gpio_ll: change API to access GPIO ports #20639

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Commits on Apr 30, 2024

  1. drivers/periph_gpio_ll: change API to access GPIO ports 

    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
    @maribu
    maribu committed Apr 30, 2024
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  2. boards/stm32: use GPIO LL for LEDs 

    This fixes a race in `LED<NUM>_TOGGLE`, which is a read-copy-write
operation. Any access to a GPIO pin on the same GPIO port that
happens concurrently could result in data corruption. Using the
GPIO LL API, which is thread-safe, fixes the issue.

Note: The used GPIO LL functions will work even in when the GPIO LL
      module is not used.
    @maribu
    maribu committed Apr 30, 2024
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