I read through the xavier-devkit schematic, and its device-tree sources.
I seems that there are missing GPIO device-tree binding for M.2 M key (PCIE NVMe) wake and alert signals.
PIN A7: for GPIO29_M2_KEYM_PEWAKE. MAIN_GPIO_PORT(S, 6).
No device-tree binding of this GPIO. From pinmux spreadsheet, is pinmux set in SDMMC1_WP mode?
PIN A55: for GPIO34_M2_KEYM_ALERT. MAIN_GPIO_PORT(P, 6).
No device-tree binding of this GPIO. From pinmux spreadsheet, it seems pinmux of this signal is set to GPIO mode.
Why device-tree binding for these two GPIO signals are missing, but they are connected in hardware?
Since the slot is M.2 Key-M to which mostly NVMe devices are connected directly (although other types of devices are connected through adapter cars) and having WAKE is of little use for NVMe devices, it is not populated in the DT.
FWIW, if it is an M.2 Key-E slot, then, mostly WiFi devices get connected to it and it makes sense to have WAKE configured for that as WOL (Wake On Lan) and WoW (Wake On Wireless) are generally used.
If you have a use case for WAKE in M.2 Key-M, please populate it in the DT.
Thanks for your reply.
I actually found out more signals that are connected in HW but no device-tree definition for them for M.2 E key.
E10: GPIO12: M.2 E GPIO12_M2_WAKE_AP, input from device to host. L15: GPIO14: M.2 E GPIO14_M2_EN, output from host to device. B55: GPIO30: M.2 E ALERT_n, input from device to host.
All signals above are NOT used on software. There is NO device-tree definition for them. Please note that they are connected to M.2 E key in hardware.