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# Zephyr BC12 Configuration
[TOC]
## Overview
The Battery Charging Specification 1.2 describes mechanisms which allow drawing
current in excess of the USB 2.0 specification. In the Zephyr EC, BC1.2 refers
to devices known as USB Charger Detectors, which allow detecting when a BC1.2
compliant charger is connected.
## Kconfig Options
The Kconfig option [`CONFIG_PLATFORM_EC_USB_CHARGER`] enables BC1.2 support in
the EC application. This option is enabled by default when
[`CONFIG_PLATFORM_EC_USBC`] is enabled. Refer to [Kconfig.usb_charger] for all
sub-options related to BC1.2 support.
## Devicetree Nodes
The BC1.2 device node is added to the I2C bus node, and the bc12 property on
the USBC port node refers to the BC1.2 device.
### Richtek RT1718S
There are two nodes describing the Richtek RT1718, one for BC1.2
[richtek,rt1718-bc12.yaml] and one for TCPC[richtek,rt1718s-tcpc.yaml]. The node
for the TCPC contains information about I2C bus and address.
### Richtek RT1739
There are two nodes describing the Richtek RT1739, one for BC1.2
[richtek,rt1739-bc12.yaml] and one for PPC [richtek,rt1739-ppc.yaml]. The node
for the PCC contains information about I2C bus and address.
### Richtek RT9490
The Richtek RT9490 is described by [richtek,rt9490-bc12.yaml]. It allows
defining which GPIO receives interrupts from the RT9490.
### Pericom PI3USB9201
The Pericom PI3USB9201 is described by [pericom,pi3usb9201.yaml]. It allows
defining which GPIO receives interrupts from the PI3USB9201. The DTS node
contains information about I2C bus and address.
## Board Specific Code
Enabling [CONFIG_PLATFORM_EC_USB_PD_5V_EN_CUSTOM] requires the board to provide
a custom `battery_is_sourcing_vbus()` function.
Some boards may implement the [board_vbus_sink_enable()] function.
## Threads
When enabled, a `usb_charger_task` will be created for each USBC port.
The task's stack size can be set using CONFIG_TASK_USB_CHG_STACK_SIZE, but
the priority is fixed. Additional information about the task priority can be
found in [shimmed_task_id.h].
## Example
Example of defining a BC1.2 chip in DTS:
```
gpio-interrupts {
compatible = "cros-ec,gpio-interrupts"
int_usb_c0_bc12: usb_c0_bc12 {
irq-pin = <&gpio_usb_c0_bc12_int_odl>;
flags = <GPIO_INT_EDGE_FALLING>;
handler = "bc12_interrupt";
};
};
&i2c2_0 {
bc12_port0: pi3usb9201@5f {
compatible = "pericom,pi3usb9201";
status = "okay";
reg = <0x5f>;
irq = <&int_usb_c0_bc12>;
};
};
port0@0 {
compatible = "named-usbc-port";
reg = <0>;
bc12 = <&bc12_port0>;
};
```
`bc12_port0` is a BC1.2 device node ("pericom,pi3usb9201" is a compatible that
is used by one of the BC1.2 devices). The `bc12_port0` is child of the `i2c2_0`
which is an I2C controller device. Each "named-usbc-port" node can point one
BC1.2 device node.
[Kconfig.usb_charger]: https://source.chromium.org/chromium/chromiumos/platform/ec/+/HEAD:zephyr/Kconfig.usb_charger
[richtek,rt1739-bc12.yaml]: https://source.chromium.org/chromium/chromiumos/platform/ec/+/HEAD:zephyr/dts/bindings/usbc/richtek,rt1739-bc12.yaml
[richtek,rt1739-ppc.yaml]: https://source.chromium.org/chromium/chromiumos/platform/ec/+/HEAD:zephyr/dts/bindings/usbc/richtek,rt1739-ppc.yaml
[richtek,rt9490-bc12.yaml]: https://source.chromium.org/chromium/chromiumos/platform/ec/+/HEAD:zephyr/dts/bindings/usbc/richtek,rt9490-bc12.yaml
[pericom,pi3usb9201.yaml]: https://source.chromium.org/chromium/chromiumos/platform/ec/+/HEAD:zephyr/dts/bindings/usbc/pericom,pi3usb9201.yaml
[shimmed_task_id.h]: https://source.chromium.org/chromium/chromiumos/platform/ec/+/HEAD:zephyr/shim/include/shimmed_task_id.h
[CONFIG_PLATFORM_EC_USB_PD_5V_EN_CUSTOM]: https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/platform/ec/zephyr/Kconfig.pd?q=%22PLATFORM_EC_USB_PD_5V_EN_CUSTOM%22
[board_vbus_sink_enable()]: https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/platform/ec/include/usb_charge.h?q=%22board_vbus_sink_enable%22
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