there's nothing this critical section protects against. both read and
write-to-clear are atomic and don't interfere with other irq futures,
only potentially with setting/clearing an irq flag from an arm core.
neither have ever been synchronized, and both have the same observable
effects under atomic writes and critical sections. (for both setting and
clearing an irq flag observable differences could only happen if the
set/clear happened after the poll read, but before the write. if it's a
clear we observe the same effects as sequencing the clear entirely after
the poll, and if it's a set we observe the same effects as sequencing
the set entirely before the poll)
it's only any good for PioPin because there it follows a pattern of gpio
pin alternate functions being named like that, everything else can just
as well be referred to as `pio::Thing`
This flag for example permits the following clock tree
configuration on stm32f103r8
let mut config = Config::default();
config.rcc.hse = Some(Hertz(16_000_000));
config.rcc.sys_ck = Some(Hertz(72_000_000));
config.rcc.pclk1 = Some(Hertz(36_000_000));
config.rcc.pclk2 = Some(Hertz(72_000_000));
config.rcc.pllxtpre = true;
Init fails if pllxtpre is false.
1429: rp pio, √9 r=Dirbaio a=pennae
another mix of refactoring and soundness issues. most notably pio pins are now checked for being actually accessible to the pio blocks, are constructible from not just the owned peripherals but refs as well, and have their registrations to the pio block reverted once all state machines and the common block has been dropped.
state machines are now also stopped when dropped, and concurrent rx+tx using dma can finally be done in a sound manner. previously it was possible to do, but allowed users to start two concurrent transfers to the same fifo using different dma channels, which obviously would not have the expected results on average.
Co-authored-by: pennae <github@quasiparticle.net>
1430: Handle SUBGHZSPI as async r=lulf a=ceekdee
For STM32WL, simplify configuration for the use of SUBGHZSPI to perform LoRa operations. Use Rx/Tx DMA on SPI to enable async functionality.
Co-authored-by: ceekdee <taigatensor@gmail.com>
Co-authored-by: Chuck Davis <taigatensor@gmail.com>
this *finally* allows sound implementions of bidirectional transfers
without blocking. the futures previously allowed only a single direction
to be active at any given time, and the dma transfers didn't take a
mutable reference and were thus unsound.
this way we can share irq handling between state machines and common
without having to duplicate the methods. it also lets us give irq flag
access to places without having to dedicate a state machine or the
common instance to those places, which can be very useful to eg trigger
an event and wait for a confirmation using an irq wait object.
we can only have one active waiter for any given irq at any given time.
allowing waits for irqs on state machines bypasses this limitation and
causes lost events for all but the latest waiter for a given irq.
splitting this out also allows us to signal from state machines to other
parts of the application without monopolizing state machine access for
the irq wait, as would be necessary to make irq waiting sound.
move all methods into PioStateMachine instead. the huge trait wasn't
object-safe and thus didn't have any benefits whatsoever except for
making it *slightly* easier to write bounds for passing around state
machines. that would be much better solved with generics-less instances.
once all sharing owners of pio pins have been dropped we should reset
the pin for use by other hal objects. unfortunately this needs an atomic
state per pio block because PioCommon and all of the state machines
really do share ownership of any wrapped pins. only PioCommon can create
them, but all state machines can keep them alive. since state machines
can be moved to core1 we can't do reference counting in relaxed mode,
but we *can* do relaxed pin accounting (since only common and the final
drop can modify this).
we can't prove that some instruction memory is not used as long as state
machines are alive, and we can pass instance memory handles between
instances as well. mark free_instr unsafe, with documentation for this caveat.
1425: rp pio, round 2 r=Dirbaio a=pennae
another round of bugfixes for pio, and some refactoring. in the end we'd like to make pio look like all the other modules and not expose traits that provide all the methods of a type, but put them onto the type itself. traits only make much sense, even if we added an AnyPio and merged the types for the member state machines (at the cost of at least a u8 per member of Pio).
Co-authored-by: pennae <github@quasiparticle.net>
not requiring a PioInstance for splitting lets us split from a
PeripheralRef or borrowed PIO as well, mirroring every other peripheral
in embassy_rp. pio pins still have to be constructed from owned pin
instances for now.
merge into PioInstance instead. PioPeripheral was mostly a wrapper
around PioInstance anyway, and the way the wrapping was done required
PioInstanceBase<N> types where PIO{N} could've been used instead.
1423: rp: fix gpio InputFuture and inefficiencies r=pennae a=pennae
InputFuture could not wait for edges without breaking due to a broken From impl, but even if the impl had been correct it would not have worked correctly because raw edge interrupts are sticky and must be cleared from software. also replace critical sections with atomic accesses, and do nvic setup only once.
Co-authored-by: pennae <github@quasiparticle.net>
doing this setup work repeatedly, on every wait, is unnecessary. with
nothing ever disabling the interrupt it is sufficient to enable it once
during device init and never touch it again.
pio control registers are notionally shared between state machines as
well. state machine operations that change these registers must use
atomic accesses (or critical sections, which would be overkill).
notably PioPin::set_input_sync_bypass was even wrong, enabling the
bypass on a pin requires the corresponding bit to be set (not cleared).
the PioCommon function got it right.
add an hd44780 example for pio. hd44780 with busy polling is a pretty
complicated protocol if the busy polling is to be done by the
peripheral, and this example exercises many pio features that we don't
have good examples for yet.
