Vendor: Cypress Semiconductor Corporation


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.

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.


Properties not inherited from the base binding file.