linuxdebug/Documentation/devicetree/bindings/soc/ti/wkup-m3-ipc.yaml

# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/soc/ti/wkup-m3-ipc.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: Wakeup M3 IPC device

maintainers:
  - Dave Gerlach <d-gerlach@ti.com>
  - Drew Fustini <dfustini@baylibre.com>

description: |+
  The TI AM33xx and AM43xx family of devices use a small Cortex M3 co-processor
  (commonly referred to as Wakeup M3 or CM3) to help with various low power tasks
  that cannot be controlled from the MPU, like suspend/resume and certain deep
  C-states for CPU Idle. Once the wkup_m3_ipc driver uses the wkup_m3_rproc driver
  to boot the wkup_m3, it handles communication with the CM3 using IPC registers
  present in the SoC's control module and a mailbox. The wkup_m3_ipc exposes an
  API to allow the SoC PM code to execute specific PM tasks.

  Wkup M3 Device Node
  ====================
  A wkup_m3_ipc device node is used to represent the IPC registers within an
  SoC.

  Support for VTT Toggle with GPIO pin
  ====================================
  On some boards like the AM335x EVM-SK and the AM437x GP EVM, a GPIO pin is
  connected to the enable pin on the DDR VTT regulator. This allows the
  regulator to be disabled upon suspend and enabled upon resume. Please note
  that the GPIO pin must be part of the GPIO0 module as only this GPIO module
  is in the wakeup power domain.

  Support for IO Isolation
  ========================
  On AM437x SoCs, certain pins can be forced into an alternate state when IO
  isolation is activated. Those pins have pad control registers prefixed by
  'CTRL_CONF_' that contain DS0 (e.g. deep sleep) configuration bits that can
  override the pin's existing bias (pull-up/pull-down) and value (high/low) when
  IO isolation is active.

  Support for I2C PMIC Voltage Scaling
  ====================================
  It is possible to pass the name of a binary file to load into the CM3 memory.
  The binary data is the I2C sequences for the CM3 to send out to the PMIC
  during low power mode entry.  

properties:
  compatible:
    enum:
      - ti,am3352-wkup-m3-ipc # for AM33xx SoCs
      - ti,am4372-wkup-m3-ipc # for AM43xx SoCs

  reg:
    description:
      The IPC register address space to communicate with the Wakeup M3 processor
    maxItems: 1

  interrupts:
    description: wkup_m3 interrupt that signals the MPU
    maxItems: 1

  ti,rproc:
    $ref: /schemas/types.yaml#/definitions/phandle
    description:
      phandle to the wkup_m3 rproc node so the IPC driver can boot it

  mboxes:
    description:
      phandles used by IPC framework to get correct mbox
      channel for communication. Must point to appropriate
      mbox_wkupm3 child node.
    maxItems: 1

  firmware-name:
    description:
      Name of binary file with I2C sequences for PMIC voltage scaling

  ti,vtt-gpio-pin:
    $ref: /schemas/types.yaml#/definitions/uint32
    description: GPIO pin connected to enable pin on VTT regulator

  ti,set-io-isolation:
    type: boolean
    description:
      If this property is present, then the wkup_m3_ipc driver will instruct
      the CM3 firmware to activate IO isolation when suspending to deep sleep.
      This can be leveraged by a board design to put other devices on the board
      into a low power state.

allOf:
  - if:
      properties:
        compatible:
          not:
            contains:
              const: ti,am4372-wkup-m3-ipc
    then:
      properties:
        ti,set-io-isolation: false

required:
  - compatible
  - reg
  - interrupts
  - ti,rproc
  - mboxes

additionalProperties: false

examples:
  - |
    /* Example for AM335x SoC */
    soc {
        #address-cells = <1>;
        #size-cells = <1>;

        am335x_mailbox: mailbox {
            #mbox-cells = <1>;
        };

        wkup_m3_ipc@1324 {
           compatible = "ti,am3352-wkup-m3-ipc";
           reg = <0x1324 0x24>;
           interrupts = <78>;
           ti,rproc = <&wkup_m3>;
           mboxes = <&am335x_mailbox &mbox_wkupm3>;
           ti,vtt-gpio-pin = <7>;
           firmware-name = "am335x-evm-scale-data.bin";
        };
    };    

  - |
    /*
     * Example for AM473x SoC:
     * On the AM437x-GP-EVM board, gpio5_7 is wired to enable pin of the DDR VTT
     * regulator. The 'ddr_vtt_toggle_default' pinmux node configures gpio5_7
     * for pull-up during normal system operation. However, the DS0 (deep sleep)
     * state of the pin is configured for pull-down and thus the VTT regulator
     * will be disabled to save power when IO isolation is active. Note that
     * this method is an alternative to using the 'ti,vtt-gpio-pin' property.
     */
    #include <dt-bindings/pinctrl/am43xx.h>
    soc {
        #address-cells = <1>;
        #size-cells = <1>;

        am437x_mailbox: mailbox {
            #mbox-cells = <1>;
        };

        am43xx_pinmux {
            pinctrl-names = "default";
            pinctrl-0 = <&ddr3_vtt_toggle_default>;

            ddr3_vtt_toggle_default: ddr_vtt_toggle_default {
                 pinctrl-single,pins = <
                    0x25C (DS0_PULL_UP_DOWN_EN | PIN_OUTPUT_PULLUP | DS0_FORCE_OFF_MODE | MUX_MODE7)
                 >;
            };
        };

        wkup_m3_ipc@1324 {
           compatible = "ti,am4372-wkup-m3-ipc";
           reg = <0x1324 0x24>;
           interrupts = <78>;
           ti,rproc = <&wkup_m3>;
           mboxes = <&am437x_mailbox &mbox_wkupm3>;
           ti,set-io-isolation;
           firmware-name = "am43x-evm-scale-data.bin";
        };
    };    

...