arch: build: interrupt: encode multi level IRQ with C macro magic

[ycsin]

This PR encodes the Zephyr multi-level interrupt using C macro magic in the devicetree, rather than depending on the gen_defines.py script during build:

zephyr/scripts/dts/gen_defines.py

Lines 435 to 441 in 1fc16e6

	def write_interrupts(node):
	# interrupts property: we have some hard-coded logic for interrupt
	# mapping here.
	#
	# TODO: can we push map_arm_gic_irq_type() and
	# encode_zephyr_multi_level_irq() out of Python and into C with
	# macro magic in devicetree.h?

zephyr/scripts/dts/gen_defines.py

Lines 456 to 469 in 1fc16e6

	def encode_zephyr_multi_level_irq(irq, irq_num):
	# See doc/kernel/services/interrupts.rst for details
	# on how this encoding works
	irq_ctrl = irq.controller
	# Look for interrupt controller parent until we have none
	while irq_ctrl.interrupts:
	irq_num = (irq_num + 1) << 8
	if "irq" not in irq_ctrl.interrupts[0].data:
	err(f"Expected binding for {irq_ctrl!r} to have 'irq' in "
	"interrupt-cells")
	irq_num |= irq_ctrl.interrupts[0].data["irq"]
	irq_ctrl = irq_ctrl.interrupts[0].controller
	return irq_num

zephyr/scripts/dts/gen_defines.py

Lines 482 to 485 in 1fc16e6

	if cell_name == "irq":
	if "arm,gic" in irq.controller.compats:
	cell_value = map_arm_gic_irq_type(irq, cell_value)
	cell_value = encode_zephyr_multi_level_irq(irq, cell_value)

This will resolve the dt & kconfig cross dependency issue encountered in #63131, and fixes #62883

After this change, the *_IRQ_IDX_x_VAL_irq of a node with an interrupt parent is the local IRQ number of that node (raw value as specified in the devicetree, or ARM GIC IRQ encoded output from gen_defines.py), rather than being multi-level encoded. The encoding of the IRQN only happens in certain DT macros, and the right one has to be used for build-time connected ISR, i.e. with IRQ_CONNECT

Fixes #62883

Important

Blocking #62907

Note

Caveat: The current approach only works for a maximum of 3 levels, I'm not sure if a while-loop equivalent like the implementation in gen_defines.py is possible with the macros, but it is what the Zephyr interrupt encoding scheme currently supports, see Multi-level Interrupt handling

[cfriedt]

Looks good to me - definitely want to get @mbolivar-ampere to go over things with a fine-tooth comb, and ensure that public DT APIs are documented.

[cfriedt]

Also worth noting, is that this is actually critical to close residual bugs from using bitmaps to encode a variable number of interrupts per level in a multi-level interrupt context, since the magic number 8 was hard-coded all over the place (python, C, etc).

As is it, the code in main is broken without this.

I believe it's also critical for multi-instance PLIC support.

[ycsin]

Force pushed a documented and cleaner version

[ycsin]

rebased

[rgundi]

LGTM

[cfriedt]

@mbolivar-ampere - would be good to get your stamp on this one.

[ycsin]

ping devicetree maintainers @mbolivar-ampere @galak

#63289 (comment)

[fkokosinski]

LGTM from the perspective of #62907.

[cfriedt]

Sorry - I twitched and merged.