According to https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/memory/Kconfig?h=v5.9 https://git.kernel.org/pub/scm/linux/kernel/g

According to https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/memory/Kconfig?h=v5.9 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin... these drivers are only used in some embedded systems. I looked at the kernel configuration for the distribution I'm using (/boot/config-`uname -r`), and CONFIG_MEMORY is not set, so none of these drivers are even available. That is: at least for desktop Linux, the firmware (not the bootloader) is the only one which sets up the physical memory controller (and actually, the only one which knows how to set up the physical memory controller; according to https://en.wikipedia.org/wiki/Coreboot#Initializing_DRAM https://en.wikipedia.org/wiki/Coreboot#Initializing_DRAM there's no public information on how to do so for modern desktop platforms).