90 lines
3.4 KiB
ReStructuredText
90 lines
3.4 KiB
ReStructuredText
.. _virtio-gpio:
|
|
|
|
Virtio-GPIO
|
|
###########
|
|
|
|
Virtio-gpio provides a virtual general-purpose input/output (GPIO) controller
|
|
that can map native GPIOs to a User VM. The User VM can perform GPIO operations
|
|
through it, including set value, get value, set direction, get direction, and
|
|
set configuration. Only Open Source and Open Drain types are currently
|
|
supported. GPIOs are often used as IRQs, typically for wakeup events.
|
|
Virtio-gpio supports level and edge interrupt trigger modes.
|
|
|
|
The virtio-gpio architecture is shown below:
|
|
|
|
.. figure:: images/virtio-gpio-1.png
|
|
:align: center
|
|
:name: virtio-gpio-1
|
|
|
|
Virtio-gpio Architecture
|
|
|
|
Virtio-gpio is implemented as a virtio legacy device in the ACRN Device
|
|
Model (DM), and is registered as a PCI virtio device to the guest OS. No
|
|
changes are required in the frontend Linux virtio-gpio except that the
|
|
guest (User VM) kernel should be built with ``CONFIG_VIRTIO_GPIO=y``.
|
|
|
|
Three virtqueues are used between FE and BE, one for GPIO
|
|
operations, one for IRQ requests, and one for IRQ event notification.
|
|
|
|
The virtio-gpio FE driver registers a gpiochip and irqchip when it is
|
|
probed. BE generates the base and number of GPIOs. Each
|
|
gpiochip or irqchip operation (for example, get_direction of gpiochip or
|
|
irq_set_type of irqchip) triggers a virtqueue_kick on its own
|
|
virtqueue. If a GPIO has been set to interrupt mode, the interrupt
|
|
events are handled within the IRQ virtqueue callback.
|
|
|
|
GPIO Mapping
|
|
************
|
|
|
|
.. figure:: images/virtio-gpio-2.png
|
|
:align: center
|
|
:name: virtio-gpio-2
|
|
|
|
GPIO mapping
|
|
|
|
- Each User VM has only one GPIO chip instance. The number of GPIOs is
|
|
based on the acrn-dm command line. The GPIO base always starts from 0.
|
|
|
|
- Each GPIO is exclusive. A User VM can't map the same native GPIO.
|
|
|
|
- For each acrn-dm, the maximum number of GPIOs is 64.
|
|
|
|
Usage
|
|
*****
|
|
|
|
Add the following parameters into the command line::
|
|
|
|
-s <slot>,virtio-gpio,<@controller_name{offset|name[=mapping_name]:offset|name[=mapping_name]:...}@controller_name{...}...]>
|
|
|
|
- **controller_name**: Input ``ls /sys/bus/gpio/devices`` to check native
|
|
GPIO controller information. Usually, the devices represent the
|
|
controller_name, and you can use it as controller_name directly. You can
|
|
also input ``cat /sys/bus/gpio/device/XXX/dev`` to get a device ID that can
|
|
be used to match ``/dev/XXX``, then use XXX as the controller_name. On MRB
|
|
and Intel NUC platforms, the controller_name values are gpiochip0, gpiochip1,
|
|
gpiochip2.gpiochip3.
|
|
|
|
- **offset|name**: You can use the GPIO offset or its name to locate one
|
|
native GPIO within the GPIO controller.
|
|
|
|
- **mapping_name**: This parameter is optional. If you want to use a customized
|
|
name for a FE GPIO, you can set a new name for a FE virtual GPIO.
|
|
|
|
Example
|
|
*******
|
|
|
|
- Map three native GPIOs to the User VM. They are native gpiochip0 with
|
|
offset of 1 and 6, and with the name ``reset``. In the User VM, the three
|
|
GPIOs have no name, and base starts from 0::
|
|
|
|
-s 10,virtio-gpio,@gpiochip0{1:6:reset}
|
|
|
|
- Map four native GPIOs to the User VM. The native gpiochip0's GPIO with offset
|
|
1 and offset 6 map to FE virtual GPIO with offset 0 and offset 1 without
|
|
names. The native gpiochip0's GPIO with name ``reset`` maps to FE virtual
|
|
GPIO with offset 2 and its name is ``shutdown``. The native gpiochip1's GPIO
|
|
with offset 0 maps to FE virtual GPIO with offset 3 and its name is
|
|
``reset``::
|
|
|
|
-s 10,virtio-gpio,@gpiochip0{1:6:reset=shutdown}@gpiochip1{0=reset}
|