Quick Boot

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Copyright

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Application Scope

This note is primarily applicable to the Linux 5.15 operating system on the Forlinx OKT527-C platform. Other platforms can also refer to it, but there may be differences between platforms, requiring modifications according to your actual requirements.

Methods for Quick Boot

The quick boot of T527 generally involves modifications to parts such as U-Boot environment variables and the kernel.
(1) Optimization of U-Boot Quick Boot

Modify the U-Boot environment variables. Change the delay bootdelay to 0 seconds to eliminate the waiting time for entering the U-Boot menu.

Open the following file:
device/config/chips/t527/configs/okt527/longan/env.cfg

Find bootdelay = 1 and change it to bootdelay = 0.

#uboot system env config
bootdelay=0					//Default delay is 1 s, change to 0

Turn off the boot0 debug information printing. Modify the following file:

device/config/chips/t527/configs/okt527/sys_config.fex
modify debug_mode to 0

[product]
version = "527"
machine = "okt527"

[platform]
eraseflag   = 0
debug_mode  = 0			//Default is 1 s, change to 0

(2) Optimization of Kernel Quick Boot

Reduce the collection of kernel printing information.

Open the following file:

kernel/linux-5.15/drivers/char/random.c

Change CRNG_READY in the last line of the following code to CRNG_EMPTY.

static enum {
        CRNG_EMPTY = 0, /* Little to no entropy collected */
        CRNG_EARLY = 1, /* At least POOL_EARLY_BITS collected */
        CRNG_READY = 2  /* Fully initialized with POOL_READY_BITS collected */
} crng_init __read_mostly = CRNG_EMPTY;
#define crng_ready() (likely(crng_init >= CRNG_EMPTY))	//默认为CRNG_READY，改为CRNG_EMPTY

Modify the serial port printing priority.

Open the following file:
device/config/chips/t527/configs/okt527/longan/env.cfg

Modify loglevel to 0

init=/init
loglevel=0			//Default is 8 s, change to 0
selinux=0

(3) Optimization of File System Startup

Trim unnecessary services that start automatically at boot to reduce the startup time.

Open the following file:

buildroot/buildroot-202205/package/allwinner/post_build.sh

Delete the /etc/preinit service by commenting out the following 7 lines.

add_preinit_to_inittab(){
        if [ -e ${TARGET_DIR}/etc/inittab ]; then
                #insert preinit
#               grep "::sysinit:/etc/preinit" ${TARGET_DIR}/etc/inittab >/dev/null
#                if [ $? -eq 0 ]; then
#                        echo "preinit is already in inittab!"
#                else
#                        echo "preinit is not in inittab, add it!"
#                        sed -i '/Startup the system/a ::sysinit:/etc/preinit' ${TARGET_DIR}/etc/inittab
#                fi		*/
                #commented ttyS0, insert /bin/sh

You can also delete unnecessary services, such as the Bluetooth service. Delete platform/forlinx/overlay_rootfs/etc/init.d/S40nxp, or rename it to 40nxp so that this service will not start.

After the modifications are completed, save the changes and exit. Then perform a full compilation, package the image, and burn it to the board. After making the above modifications, the boot test shows that the device can start up in about 7 - 8 seconds.