I want to boot an ARM Linux board (Allwinner H3 for example) from a generic (micro) SD card through an SPI interface. Can an SD card accept SPI communication right away or is there any "SPI mode initialization" needed on the card?
I must admit I have not gone through all the SD documentation and examples available (like linked in this answer) as I am not on such a low level like Arduino but on a Linux system instead.
This post says an SD card needs to be "switched" to SPI mode first and I am not sure how this is compatible with the SPI boot process in Linux. Can someone explain please?
Edit: The reason for booting from SPI on a Linux board that has a micro SD card slot is that I want to use this slot as a secondary removable storage only (for saving photos etc.) and want to have a system on different SD card that will be directly soldered to the SPI interface (possibly without intermediate board/controller).