# Copyright (c) 2018 Foundries.io
# Copyright (c) 2020 ATL Electronics
# SPDX-License-Identifier: Apache-2.0

description: |
  Cypress Interrupt Multiplex

  The PSoC-6 Cortex-M0+ NVIC can handle up to 32 interrupts. This means that
  user can select up to 32 interrupts sources from the 240 possible vectors
  to be processed in the Cortex-M0+ CPU.

  At CPU Sub System (CPUSS) there are 8 special registers (intmux[0~7]) to
  configure the 32 NVIC lines for Cortex-M0+ CPU. Each register handles up to
  4 interrupt sources by grouping intmux channels. These means that each byte
  from intmux[0~7] store a 'vector number' which selects the peripheral
  interrupt source in the multiplexer. The multiplexer is placed before
  Cortex-M0+ NVIC controller. Note that Cortex-M4 have all interrupt sources
  directly connected to NVIC and doesn't require any special configuration.

  On a general view, the below represents the Interrupt Multiplexer
  configuration and how the Cortex-M0+ NVIC sources are organized. Each
  channel chX represents a Cortex-M0+ NVIC line and it stores a vector number.
  The vector number selects the PSoC-6 peripheral interrupt source for the
  Cortex-M0+ NVIC controller line.

  intmux[0] = {ch03, ch02, ch01, ch00}
  intmux[1] = {ch07, ch06, ch05, ch04}
  ...
  intmux[7] = {ch31, ch30, ch29, ch28}

  In pratical terms, the Cortex-M0+ requires user to define all NVIC interrupt
  sources and the proper NVIC interrupt order. With that, the system configures
  the Cortex-M0+ Interrupt Multiplexer and interrupts can be processed.
  More information about it at PSoC-6 Architecture Technical Reference Manual,
  section CPU Sub System (CPUSS) Registers.


  The below fragment configure the GPIO Port 0 to generate an interrupt at
  Cortex-M0+ NVIC:

  At psoc6.dtsi file the gpio_prt0 peripheral had the interrupt source 2:

  gpio_prt0: gpio@40320100 {
    interrupts = <2 1>;
  };

  In order to enable gpio_prt0 interrupt at Cortex-M0+ an interrupt parent
  must be defined at gpio_prt0 node selecting the Interrupt Multiplex Channel.
  This can be defined at <board>_m0.dts file:

  &gpio_prt0 {
    interrupt-parent = <&intmux_ch20>;
  };

  The translation of these two definitions is:
         CH   REGS  INT NUM    CH   CH/REG
  intmux[20 mod 8] |= 0x02 << (20 mod 4);

  These results in Cortex-M0+ NVIC line 20 handling PSoC-6 interrupt source 2.
  The interrupt can be enabled/disable at NVIC at line 20 as usual.

  Notes:
  1) Multiple definitions will generate multiple interrutps
  2) The interrupt sources are shared between Cortex-M0+/M4. These means, can
     trigger action in parallel in both processors.
  3) User can change priority at Cortex-M0+ NVIC by changing interrupt channels
     at interrupt-parent properties.
  4) Only the peripherals used by Cortex-M0+ should be configured.

compatible: "cypress,psoc6-intmux"

include: base.yaml

properties:
  reg:
    required: true
