mirror of
https://github.com/projectacrn/acrn-hypervisor.git
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237997f3f9
First pass at updating obsolete usage of "UOS" and "SOS" Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
90 lines
3.4 KiB
ReStructuredText
90 lines
3.4 KiB
ReStructuredText
.. _virtio-gpio:
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Virtio-gpio
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###########
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virtio-gpio provides a virtual GPIO controller, which will map part of
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native GPIOs to User VM, User VM can perform GPIO operations through it,
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including setting values, including set/get value, set/get direction and
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set configuration (only Open Source and Open Drain types are currently
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supported). GPIOs quite often be used as IRQs, typically for wakeup
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events, virtio-gpio supports level and edge interrupt trigger modes.
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The virtio-gpio architecture is shown below
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.. figure:: images/virtio-gpio-1.png
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:align: center
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:name: virtio-gpio-1
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Virtio-gpio Architecture
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Virtio-gpio is implemented as a virtio legacy device in the ACRN device
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model (DM), and is registered as a PCI virtio device to the guest OS. No
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changes are required in the frontend Linux virtio-gpio except that the
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guest (User VM) kernel should be built with ``CONFIG_VIRTIO_GPIO=y``.
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There are three virtqueues used between FE and BE, one for gpio
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operations, one for irq request and one for irq event notification.
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Virtio-gpio FE driver will register a gpiochip and irqchip when it is
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probed, the base and number of gpio are generated by the BE. Each
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gpiochip or irqchip operation(e.g. get_direction of gpiochip or
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irq_set_type of irqchip) will trigger a virtqueue_kick on its own
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virtqueue. If some gpio has been set to interrupt mode, the interrupt
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events will be handled within the irq virtqueue callback.
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GPIO mapping
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************
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.. figure:: images/virtio-gpio-2.png
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:align: center
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:name: virtio-gpio-2
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GPIO mapping
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- Each User VM has only one GPIO chip instance, its number of GPIO is
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based on acrn-dm command line and GPIO base always start from 0.
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- Each GPIO is exclusive, User VM can’t map the same native gpio.
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- Each acrn-dm maximum number of GPIO is 64.
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Usage
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*****
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Add the following parameters into the command line::
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-s <slot>,virtio-gpio,<@controller_name{offset|name[=mapping_name]:offset|name[=mapping_name]:…}@controller_name{…}…]>
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- **controller_name**: Input “ls /sys/bus/gpio/devices” to check native
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gpio controller information.Usually, the devices represent the
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controller_name, you can use it as controller_name directly. You can
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also input “cat /sys/bus/gpio/device/XXX/dev” to get device id that can
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be used to match /dev/XXX, then use XXX as the controller_name. On MRB
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and NUC platforms, the controller_name are gpiochip0, gpiochip1,
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gpiochip2.gpiochip3.
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- **offset|name**: you can use gpio offset or its name to locate one
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native gpio within the gpio controller.
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- **mapping_name**: This is optional, if you want to use a customized
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name for a FE gpio, you can set a new name for a FE virtual gpio.
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Example
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*******
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- Map three native gpio to User VM, they are native gpiochip0 with
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offset of 1 and 6, and with the name “reset”. In User VM, the three
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gpio has no name, and base from 0.::
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-s 10,virtio-gpio,@gpiochip0{1:6:reset}
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- Map four native gpio to User VM, native gpiochip0’s gpio with offset 1
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and offset 6 map to FE virtual gpio with offset 0 and offset 1
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without names, native gpiochip0’s gpio with name “reset” maps to FE
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virtual gpio with offset 2 and its name is “shutdown”, native
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gpiochip1’s gpio with offset 0 maps to FE virtual gpio with offset 3 and
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its name is “reset”.::
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-s 10,virtio-gpio,@gpiochip0{1:6:reset=shutdown}@gpiochip1{0=reset}
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