Boot directly to linux kernel without u-boot.

lectric_univers

I've been reading up on this technique. But I'm not finding enough information for me to completely understand how to do this. But that doesn't stop me from pursuing this. The advantages are faster boot times, less code to maintain, and simpler setup if it can be done. Also power savings since if the boot is fast enough there's no need for sleep/hibernate/etc modes to conserve power. The board can just be shut off and restarted. The boot will be faster than waking up from sleep/hibernate.



One paper got boot times to be around 0.5 seconds to boot/reboot.


Anyone tried?

Links: (Happy Reading!)

• http://infocenter.arm.com/help/topic/com.arm.doc.dai0527a/DAI0527A_baremetal_boot_code_for_ARMv8_A_processors.pdf
• https://events.static.linuxfound.org/images/stories/pdf/lcna_co2012_marinas.pdf
• https://www.arm.com/files/downloads/ARMv8_Architecture.pdf
• https://events.static.linuxfound.org/sites/events/files/slides/praesentation.pdf
• https://events.static.linuxfound.org/sites/events/files/slides/linuxcon-japan-2016-softwre-updates-sangorrin.pdf
  
  

A13

1. Booting directly into Linux would be at least difficult if its possible at all.
The Standard boot prcess of a Allwinner based Board is BROM  -> SPL ( Uboot ) -> Kernel -> rootfs

The first Bootloader ( Bootrom or short BROM ) looks for the second stage bootloader which is then executet inside of the internal ram of the SOC. The second Stage Bootloader initializes the DDR RAM and other Hardware components an the loads the Kernel into ram.

dmx512

The Boot process -> https://linux-sunxi.org/Boot_Process
U-Boot is a prerequiste.

You can check with the debug UART if U-Boot is waiting seconds for keyboard input. When you remove this option, then the boot process will be quikcer.

grabdexter

U-Boot adds two capabilities to the boot process that the Xilinx FSBL does not have. (1) It reads files used at boot time from the SD Card instead of requiring them to be included in the boot.bin, and (2) it has a command line, in case you want to modify boot parameters at boot time.

If you do not need either of those capabilities, then booting Linux directly from FSBL saves some time during boot and reduces the number of chip/board specific files that need to be maintained.

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