Describes the gpio rpmsg transport protocol over the rpmsg bus between the cores.
Signed-off-by: Shenwei Wang <[email protected]> --- Documentation/driver-api/gpio/gpio-rpmsg.rst | 232 +++++++++++++++++++ Documentation/driver-api/gpio/index.rst | 1 + 2 files changed, 233 insertions(+) create mode 100644 Documentation/driver-api/gpio/gpio-rpmsg.rst diff --git a/Documentation/driver-api/gpio/gpio-rpmsg.rst b/Documentation/driver-api/gpio/gpio-rpmsg.rst new file mode 100644 index 000000000000..c78d10a9a85c --- /dev/null +++ b/Documentation/driver-api/gpio/gpio-rpmsg.rst @@ -0,0 +1,232 @@ +.. SPDX-License-Identifier: GPL-2.0-or-later + +GPIO RPMSG Protocol +=================== + +The GPIO RPMSG transport protocol is used for communication and interaction +with GPIO controllers located on remote cores on the RPMSG bus. + +Message Format +-------------- + +The RPMSG message consists of a 14-byte packet with the following layout: + +.. code-block:: none + + +-----+-------+--------+-----+-----+------------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | ID |vendor |version |type |cmd |reserved[5] |line |port | data | + +-----+-------+--------+-----+-----+------------+-----+-----+-----+----+ + +- **ID (Message Identification Code)**: Always be 0x5. Indicates the GPIO message. + +- **Vendor**: Vendor ID number. + - 0: Reserved + - 1: NXP + +- **Version**: Vendor-specific version number (such as software release). + +- **Type (Message Type)**: The message type can be one of: + + - 0: GPIO_RPMSG_SETUP + - 1: GPIO_RPMSG_REPLY + - 2: GPIO_RPMSG_NOTIFY + +- **Cmd**: Command code, used for GPIO_RPMSG_SETUP messages. + +- **reserved[5]**: Reserved bytes. Should always be 0. + +- **line**: The GPIO line index. + +- **port**: The GPIO controller index. + +- **data**: See details in the command description below. + +GPIO Commands +------------- + +Commands are specified in the **Cmd** field for **GPIO_RPMSG_SETUP** (Type=0) messages. + +The SETUP message is always sent from Linux to the remote firmware. Each +SETUP corresponds to a single REPLY message. The GPIO driver should +serialize messages and determine whether a REPLY message is required. If a +REPLY message is expected but not received within the specified timeout +period (currently 1 second in the Linux driver), the driver should return +-ETIMEOUT. + +GPIO_RPMSG_INPUT_INIT (Cmd=0) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +**Request:** + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | 5 | 1 | 0 | 0 | 0 | 0 |line |port | val | wk | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + +- **val**: Interrupt trigger type. + + - 0: Interrupt disabled + - 1: Rising edge trigger + - 2: Falling edge trigger + - 3: Both edge trigger + - 4: Low level trigger + - 5: High level trigger + +- **wk**: Wakeup enable. + + The remote system should always aim to stay in a power-efficient state by + shutting down or clock-gating the GPIO blocks that aren't in use. Since + the remoteproc driver is responsibe for managing the power states of the + remote firmware, the GPIO driver does not require to konow the firmware's + running states. + + When the wakeup bit is set, the remote firmware should configure the line + as a wakeup source. The firmware should send the notification message to + Linux after it is woken from the GPIO line. + + - 0: Disable wakeup from GPIO + - 1: Enable wakeup from GPIO + +**Reply:** + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | 5 | 1 | 0 | 1 | 1 | 0 |line |port | err | 0 | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + +- **err**: Error code from the remote core. + + - 0: Success + - 1: General error (early remote software only returns this unclassified error) + - 2: Not supported (A command is not supported by the remote firmware) + - 3: Resource not available (The resource is not allocated to the Linux) + - 4: Resource busy (The resource is already used) + - 5: Parameter error + +GPIO_RPMSG_OUTPUT_INIT (Cmd=1) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +**Request:** + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | 5 | 1 | 0 | 0 | 1 | 0 |line |port | val | 0 | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + +- **val**: Output level. + + - 0: Low + - 1: High + +**Reply:** + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | 5 | 1 | 0 | 1 | 1 | 0 |line |port | err | 0 | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + +- **err**: See above for definitions. + +GPIO_RPMSG_INPUT_GET (Cmd=2) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +**Request:** + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | 5 | 1 | 0 | 0 | 2 | 0 |line |port | 0 | 0 | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + +**Reply:** + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+-----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D | + | 5 | 1 | 0 | 1 | 2 | 0 |line |port | err |level| + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+-----+ + +- **err**: See above for definitions. + +- **level**: Input level. + + - 0: Low + - 1: High + +GPIO_RPMSG_GET_DIRECTION (Cmd=3) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +**Request:** + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | 5 | 1 | 0 | 0 | 3 | 0 |line |port | 0 | 0 | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + +**Reply:** + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+-----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D | + | 5 | 1 | 0 | 1 | 3 | 0 |line |port | err | dir | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+-----+ + +- **err**: See above for definitions. + +- **dir**: Direction. + + - 0: Output + - 1: Input + +Notification Message +-------------------- + +Notifications are sent with **Type=2 (GPIO_RPMSG_NOTIFY)**: + +When a GPIO line asserts an interrupt on the remote processor, the firmware +should immediately mask the corresponding interrupt source and send a +notification message to the Linux. Upon completion of the interrupt +handling on the Linux side, the driver should issue a +**GPIO_RPMSG_INPUT_INIT** command to the firmware to unmask the interrupt. + +A Notification message can arrive between a SETUP and its REPLY message, +and the driver is expected to handle this scenario. + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | 5 | 1 | 0 | 2 | 0 | 0 |line |port | 0 | 0 | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + +- **line**: The GPIO line index. +- **port**: The GPIO controller index. + +The reply message for the notification is optional. The remote firmware can +implement it to simulate the interrupt acknowledgment behavior. + +The notification reply is sent with the byte index 0x4=1. + +.. code-block:: none + + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + |0x00 |0x01 |0x02 |0x03 |0x04 |0x05..0x09 |0x0A |0x0B |0x0C |0x0D| + | 5 | 1 | 0 | 2 | 1 | 0 |line |port | 0 | 0 | + +-----+-----+-----+-----+-----+-----------+-----+-----+-----+----+ + +- **line**: The GPIO line index. +- **port**: The GPIO controller index. diff --git a/Documentation/driver-api/gpio/index.rst b/Documentation/driver-api/gpio/index.rst index bee58f709b9a..e5eb1f82f01f 100644 --- a/Documentation/driver-api/gpio/index.rst +++ b/Documentation/driver-api/gpio/index.rst @@ -16,6 +16,7 @@ Contents: drivers-on-gpio bt8xxgpio pca953x + gpio-rpmsg Core ==== -- 2.43.0
