Booting The Linux Kernel - MNT Reform Operator's Handbook Manual

MNT Reform Operator Handbook

8.3 Booting the Linux Kernel

Theoretically, you could boot other operating systems besides Linux, such as FreeBSD, NetBSD, OpenBSD
or anything else that supports the i.MX6QP SoC. So far, we didn't have the time to test them, though. We'll
happily expand this guide with your contributions if you've managed to run an alternative OS on Reform.
The default boot commands for U-Boot are specified at https://github.com/mntmn/u-boot/blob/
mntreform/include/configs/mntreform.h#L104
If you want to boot manually, these are the steps.
1. Configure the kernel command line to use no initial ram disk, use the first partition of the first SD card as
the root volume (read/write), and wait for the root device. Also, set the continuous memory allocation
(CMA) pool to 256MB and disable message signaled interrupts (MSI) for PCI express. The CMA pool
is needed by the etnaviv GPU drivers. MSI has to be disabled for some expansions like ath9k-based WiFi
cards.
setenv bootargs noinitrd root=/dev/mmcblk0p1 rw rootwait cma=256M pci=nomsi no_
console_suspend=1
→
2. Set the maximum address/size for the device tree structure (called FDT in U-Boot, DTS/DTB in Linux).
The kernel can fail to start without this.
setenv fdt_high 0xffffffff
3. Load the Kernel (zImage) to address 0x10008000 from the SD card (also called "MMC") device 0, par-
tition 1 (there is no partition 0, 1 is the first). ext4load works for ext4 formatted partitions. For FAT, you
would use fatload.
ext4load mmc 0:1 0x10008000 zImage
4. Load the device tree (FDT/DTB) to address 0x18000000 from the same partition.
ext4load mmc 0:1 0x18000000 imx6qp-mntreform.dtb
5. Tell U-Boot where you just loaded the FDT and to please resize it.
fdt addr 0x18000000
fdt resize
6. Start Linux from the load address and pass the FDT address to it.
bootz 0x10008000 - 0x18000000
30 Chapter 8. System Boot Details