# Copyright (c) 2020 Gerson Fernando Budke <nandojve@gmail.com>
# SPDX-License-Identifier: Apache-2.0

description: |
  Atmel SAM4L Family I2C (TWIM) node

  The Atmel Two-wire Master Interface (TWIM) interconnects components on a
  unique two-wire bus, made up of one clock line and one data line with speeds
  of up to 3.4 Mbit/s, based on a byte-oriented transfer format.  The TWIM is
  always a bus master and can transfer sequential or single bytes.  Multiple
  master capability is supported.  Arbitration of the bus is performed
  internally and relinquishes the bus automatically if the bus arbitration is
  lost.

  When using speeds above standard mode, user may need adjust clock and data
  lines slew and strength parameters.  In general, slew 0 and minimal strength
  is enougth for short buses and light loads.  As reference, the below
  is the lowest power configuration:

    std-clk-slew-lim = <0>;
    std-clk-strength-low = "0.5";
    std-data-slew-lim = <0>;
    std-data-strength-low = "0.5";

    hs-clk-slew-lim = <0>;
    hs-clk-strength-high = "0.5";
    hs-clk-strength-low = "0.5";
    hs-data-slew-lim = <0>;
    hs-data-strength-low = "0.5";

  For best performances, user can tune the slope curves using an osciloscope.
  The tuning should be performed by groups defined <mode>-<line>.  The prefix
  std-<line> configures fast/fast-plus mode speeds and hs-<line> selects the
  high speed mode.  The tune should be performed for both clock and data lines
  on both speed modes.


compatible: "atmel,sam-i2c-twim"

include: i2c-controller.yaml

properties:
    reg:
      required: true

    interrupts:
      required: true

    peripheral-id:
      type: int
      required: true
      description: peripheral ID

    std-clk-slew-lim:
      type: int
      required: true
      description: |
        Slew limit of the TWCK output buffer.  This should be adjusted with
        std-clk-strength-low to fine tune the TWCK slope.
      enum:
        - 0
        - 1
        - 2
        - 3

    std-clk-strength-low:
      type: string
      required: true
      description: |
        Pull-down drive strength of the TWCK output buffer in fast/fast plus
        mode.  This should be adjusted to provide proper TWCK line fall time.
        The value represents the port output current in mA when signal on
        low level.
      enum:
        - "0.5"
        - "1.0"
        - "1.6"
        - "3.1"
        - "6.2"
        - "9.3"
        - "15.5"
        - "21.8"

    std-data-slew-lim:
      type: int
      required: true
      description: |
        Slew limit of the TWD output buffer.  This should be adjusted with
        std-data-strength-low to fine tune the TWD slope.
      enum:
        - 0
        - 1
        - 2
        - 3

    std-data-strength-low:
      type: string
      required: true
      description: |
        Pull-down drive strength of the TWD output buffer in fast/fast plus
        mode.  This should be adjusted to provide proper TWD line fall time.
        The value represents the port output current in mA when signal on
        low level.
      enum:
        - "0.5"
        - "1.0"
        - "1.6"
        - "3.1"
        - "6.2"
        - "9.3"
        - "15.5"
        - "21.8"

    hs-clk-slew-lim:
      type: int
      required: true
      description: |
        Slew limit of the TWCK output buffer in high speed mode.  This
        should be adjusted with both hs-clk-strength-high and
        hs-clk-strength-low to fine tune the TWCK slope.
      enum:
        - 0
        - 1
        - 2
        - 3

    hs-clk-strength-high:
      type: string
      required: true
      description: |
        Pull-up drive strength of the TWCK output buffer in high speed
        mode.  This should be adjusted to provide proper TWCK line rise time.
        The value represents the port output current in mA when signal on
        high level.
      enum:
        - "0.5"
        - "1.0"
        - "1.5"
        - "3.0"

    hs-clk-strength-low:
      type: string
      required: true
      description: |
        Pull-down drive strength of the TWCK output buffer in high speed
        mode.  This should be adjusted to provide proper TWCK line fall time.
        The value represents the port output current in mA when signal on
        low level.
      enum:
        - "0.5"
        - "1.0"
        - "1.6"
        - "3.1"
        - "6.2"
        - "9.3"
        - "15.5"
        - "21.8"

    hs-data-slew-lim:
      type: int
      required: true
      description: |
        Slew limit of the TWD output buffer in high speed mode.  This
        should be adjusted with hs-data-strength-low to fine tune the TWD
        slope.
      enum:
        - 0
        - 1
        - 2
        - 3

    hs-data-strength-low:
      type: string
      description: |
        Pull-down drive strength of the TWD output buffer in high speed
        mode.  This should be adjusted to provide proper TWD line fall time.
        The value represents the port output current in mA when signal on
        low level.
      enum:
        - "0.5"
        - "1.0"
        - "1.6"
        - "3.1"
        - "6.2"
        - "9.3"
        - "15.5"
        - "21.8"

    hs-master-code:
      type: int
      required: true
      description: |
        3-bit code to be prefixed with 0b00001 to form a unique
        8-bit HS-mode master code (0000 1XXX)
      enum:
        - 0   # 000
        - 1   # 001
        - 2   # 010
        - 3   # 011
        - 4   # 100
        - 5   # 101
        - 6   # 110
        - 7   # 111

    pinctrl-0:
      type: phandles
      required: true
      description: |
        GPIO pin configuration for TWCK & TWD signals. We expect that
        the phandles will reference pinctrl nodes. These nodes will
        have a nodelabel that matches the Atmel SoC HAL defines and
        be of the form p<port><pin><periph>_<inst>_<signal>.

        For example the I2C on SAM4L would be
           pinctrl-0 = <&pb0a_twi1_twd1 &pb1a_twi1_twck1>;