from migen.fhdl.std import *
from migen.genlib.fsm import FSM, NextState
from migen.bank.description import *
from migen.bank.eventmanager import *
from migen.flow.actor import *
from migen.actorlib import dma_lasmi

# Slot status: EMPTY=0 LOADED=1 PENDING=2
class _Slot(Module, AutoCSR):
	def __init__(self, addr_bits, alignment_bits):
		self.ev_source = EventSourceLevel()
		self.address = Signal(addr_bits)
		self.address_reached = Signal(addr_bits)
		self.address_valid = Signal()
		self.address_done = Signal()

		self._r_status = CSRStorage(2, write_from_dev=True)
		self._r_address = CSRStorage(addr_bits + alignment_bits, alignment_bits=alignment_bits, write_from_dev=True)

		###

		self.comb += [
			self.address.eq(self._r_address.storage),
			self.address_valid.eq(self._r_status.storage[0]),
			self._r_status.dat_w.eq(2),
			self._r_status.we.eq(self.address_done),
			self._r_address.dat_w.eq(self.address_reached),
			self._r_address.we.eq(self.address_done),
			self.ev_source.trigger.eq(self._r_status.storage[1])
		]

class _SlotArray(Module, AutoCSR):
	def __init__(self, nslots, addr_bits, alignment_bits):
		self.submodules.ev = EventManager()
		self.address = Signal(addr_bits)
		self.address_reached = Signal(addr_bits)
		self.address_valid = Signal()
		self.address_done = Signal()

		###

		slots = [_Slot(addr_bits, alignment_bits) for i in range(nslots)]
		for n, slot in enumerate(slots):
			setattr(self.submodules, "slot"+str(n), slot)
			setattr(self.ev, "slot"+str(n), slot.ev_source)
		self.ev.finalize()

		change_slot = Signal()
		current_slot = Signal(max=nslots)
		self.sync += If(change_slot, [If(slot.address_valid, current_slot.eq(n)) for n, slot in reversed(list(enumerate(slots)))])
		self.comb += change_slot.eq(~self.address_valid | self.address_done)

		self.comb += [
			self.address.eq(Array(slot.address for slot in slots)[current_slot]),
			self.address_valid.eq(Array(slot.address_valid for slot in slots)[current_slot])
		]
		self.comb += [slot.address_reached.eq(self.address_reached) for slot in slots]
		self.comb += [slot.address_done.eq(self.address_done & (current_slot == n)) for n, slot in enumerate(slots)]

class DMA(Module):
	def __init__(self, lasmim, nslots):
		bus_aw = lasmim.aw
		bus_dw = lasmim.dw
		alignment_bits = bits_for(bus_dw//8) - 1

		fifo_word_width = 24*bus_dw//32
		self.frame = Sink([("sof", 1), ("pixels", fifo_word_width)])
		self._r_frame_size = CSRStorage(bus_aw + alignment_bits, alignment_bits=alignment_bits)
		self.submodules._slot_array = _SlotArray(nslots, bus_aw, alignment_bits)
		self.ev = self._slot_array.ev

		###

		# address generator + maximum memory word count to prevent DMA buffer overrun
		reset_words = Signal()
		count_word = Signal()
		last_word = Signal()
		current_address = Signal(bus_aw)
		mwords_remaining = Signal(bus_aw)
		self.comb += [
			self._slot_array.address_reached.eq(current_address),
			last_word.eq(mwords_remaining == 1)
		]
		self.sync += [
			If(reset_words,
				current_address.eq(self._slot_array.address),
				mwords_remaining.eq(self._r_frame_size.storage)
			).Elif(count_word,
				current_address.eq(current_address + 1),
				mwords_remaining.eq(mwords_remaining - 1)
			)
		]

		# 24bpp -> 32bpp
		memory_word = Signal(bus_dw)
		pixbits = []
		for i in range(bus_dw//32):
			for j in range(3):
				b = (i*3+j)*8
				pixbits.append(self.frame.pixels[b+6:b+8])
				pixbits.append(self.frame.pixels[b:b+8])
			pixbits.append(0)
			pixbits.append(0)
		self.comb += memory_word.eq(Cat(*pixbits))

		# bus accessor
		self.submodules._bus_accessor = dma_lasmi.Writer(lasmim)
		self.comb += [
			self._bus_accessor.address_data.a.eq(current_address),
			self._bus_accessor.address_data.d.eq(memory_word)
		]

		# control FSM
		fsm = FSM()
		self.submodules += fsm

		fsm.act("WAIT_SOF",
			reset_words.eq(1),
			self.frame.ack.eq(~self._slot_array.address_valid | ~self.frame.sof),
			If(self._slot_array.address_valid & self.frame.sof & self.frame.stb, NextState("TRANSFER_PIXELS"))
		)
		fsm.act("TRANSFER_PIXELS",
			self.frame.ack.eq(self._bus_accessor.address_data.ack),
			If(self.frame.stb,
				self._bus_accessor.address_data.stb.eq(1),
				If(self._bus_accessor.address_data.ack,
					count_word.eq(1),
					If(last_word, NextState("EOF"))
				)
			)
		)
		fsm.act("EOF",
			If(~self._bus_accessor.busy,
				self._slot_array.address_done.eq(1),
				NextState("WAIT_SOF")
			)
		)

	def get_csrs(self):
		return [self._r_frame_size] + self._slot_array.get_csrs()