Merged for the Linux 7.0 kernel was a power sequencing driver for PCIe M.2 connectors as part of an effort to allow describing PCIe M.2 connectors in Device Tree files. For Linux 7.1, that driver is extending support for PCIe M.2 Key E connectors.
Qualcomm engineers worked through the support for extending the “pwrseq-pcie-m2” drivers to also support PCIe M.2 Key E connectors, such as is used commonly for wireless WiFi/Bluetooth adapters, some NFC devices, and more.
Manivannan Sadhasivam of Qualcomm explained in enabling the Key E connectors in this power sequencing driver:
“Add support for handling the power sequence of the PCIe M.2 Key E connectors. These connectors are used to attach the Wireless Connectivity devices to the host machine including combinations of WiFi, BT, NFC using interfaces such as PCIe/SDIO for WiFi, USB/UART for BT and I2C for NFC.
Currently, this driver supports only the PCIe interface for WiFi and UART interface for BT. The driver also only supports driving the 3.3v/1.8v power supplies and W_DISABLE{1/2}# GPIOs. The optional signals of the Key E connectors are not currently supported.”
This support is the heart of the power sequencing pull request already sent out for the now-open Linux 7.1 merge window.
