4.1 ATWILC Power Control

The host controls the ATWILC device’s power using two pins, CHIP_EN and RESET. If these pins are connected to the host's GPIO pins, it is recommended that the device tree file be modified as explained in 4.5 General Purpose IOs. Therefore, the driver can retrieve information from the GPIOs connected to ATWILC's CHIP_EN and RESET.

Other hardware designs connect the CHIP_EN and RESET to the power line using an RC network, which ensures that the ATWILC device is powered on with the host. In this case, these APIs are not required and it is recommended that they be modified to avoid changing the GPIO configurations that might be already used for another function.

Note: When ATWILC’s module is loaded to the Linux kernel, it communicates with the ATWILC's SDIO/SPI controller. Upon success, it calls the corresponding probing function, which initializes the rest of the driver. The Linux kernel must find the SDIO/SPI controller prior to ATWILC's driver initialization. Therefore, the user must ensure that ATWILC is powered-up prior to initialization.