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AM6254 Embedded Platform: Optimization Scheme for Shortening U-boot Boot Time
Introduction to the U-Boot boot process
U-Boot Boot Process Stage 1
Main process Partial Hardware Initialization -> Load Full U-Boot into RAM -> Jump to Stage 2 Entry for Execution.
Files Used Mainly in Stage 1 (Non-Open Source Scenario):
- start.S (Hardware Initialization, watchdog, interrupts, clock configurations)
- lowlevel_init.S (RAM (DDR) initialization, U-Boot code loading, stack setup, BSS clearing, jump to U-Boot Stage 2
U-Boot Boot Process Stage 2
Stage 2 involves further hardware initialization by U-Boot, configuring command line parameters and environment variables, and transitioning to the kernel.
The main documents used are:
- board.c file: Typically, our own files are located in the board/forlinx/ directory.
- main.c file: Located in the common directory
Main function
Some of the more important initialisation functions are as follows:
1.''setup_mon_len'' function: Set the ''gd'' structure's ''mon_len'' member variable, representing the length of the entire code;
2.''initf_malloc'' function: Sets the ''gd '' structure's member variables related to ''malloc'';
3.''board_early_init_f''function;
4.To initialize the IO configuration of the serial port, defined in the board/freescale/mx6ull_toto/mx6ull_toto.cfile;
5.''timer_init'' function: Initialize the kernel timer to provide clock ticks for U-Boot, defined in the ''arch/arm/imxcommon/timer.c''file;
6.''get_clocks'' function: Retrieve the clock for the SD card peripheral (sdhc_clk), defined in the arch/arm/imxcommon/speed.c file;
7.''init_baud_rate'' function: Initialize the baud rate, defined in the ''common/board_f.c'' file.
8.''serial_init'' function: Initialize serial communication settings, defined in the''drivers/serial/serial.c''file;
9.''console_init_f'' function: Initialize the console, defined in the ''common/console.c'' file;
10.''display_options'' function: Print U-Boot version information and compilation details, defined in the lib/display_options.c file;
11.''print_cpuinfo'' function: To display CPU information and the main clock frequency, defined in the arch/arm/imx-common/cpu.c file;
12.''show_board_info'' function: Print development board information, defined in the common/board _ info.c file;
13.''init_func_i2c'' function: To initialize I2C;
14.''announce_dram_init'' function: This function is simple, it outputs the string "DRAM:";
15.''dram_init'' function: Doesn't actually initialize DDR but rather sets the value of gd->ram_size.
Current U-boot startup print information
U-Boot SPL 2021.01-gd1345267-dirty (Jul 08 2023 - 08:00:49 +0800) SYSFW ABI: 3.1 (firmware rev 0x0015 '21.5.1--w2022.07-am62x (Terrifi') am625_init: board_init_f done(counter=1) SPL initial stack usage: 13768 bytes i2c_write: error waiting for data ACK (status=0x116) i2c_write: error waiting for data ACK (status=0x116) Auth Success! normal mode am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 Trying to boot from MMC1 am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 Loading Environment from MMC... MMC: block number 0x3500 exceeds max(0x2000) *** Warning - !read failed, using default environment am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 init_env from device 9 not supported! Starting ATF on ARM64 core... NOTICE: BL31: v2.5(release):v0.6-6-gd489c56b NOTICE: BL31: Built : 15:08:18, Jun 26 2023 U-Boot SPL 2021.01-gd1345267-dirty (Jul 08 2023 - 08:00:56 +0800) SYSFW ABI: 3.1 (firmware rev 0x0015 '21.5.1--w2022.07-am62x (Terrifi') am625_init: board_init_f done am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 Trying to boot from MMC1 am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 U-Boot 2021.01-gd1345267-dirty (Jul 08 2023 - 08:00:56 +0800) SoC: AM62X SR1.0 Model: Forlinx OK62xx-C board DRAM: 2 GiB MMC: mmc@fa10000: 0, mmc@fa00000: 1 Loading Environment from MMC... OK In: serial@2800000 Out: serial@2800000 Err: serial@2800000 52334 bytes read in 5 ms (10 MiB/s) Saving Environment to MMC... Writing to MMC(0)... OK Net: eth0: ethernet@8000000 Autoboot in 1 seconds switch to partitions #0, OK mmc0(part 0) is current device SD/MMC found on device 0 Failed to load 'boot.scr' Failed to load 'uEnv.txt' MMC: no card present 20208128 bytes read in 111 ms (173.6 MiB/s) 52334 bytes read in 5 ms (10 MiB/s) 4595 bytes read in 5 ms (897.5 KiB/s) ## Flattened Device Tree blob at 88000000 Booting using the fdt blob at 0x88000000 Loading Device Tree to 000000008fef0000, end 000000008fffffff ... OK
U-boot shortens 2 seconds of boot time by disabling USB and Ethernet via defconfig.Modify the autoboot.c file to hardcode bootdelay=0, reducing it by 1 second.
diff --git a/common/autoboot.c b/common/autoboot.c index e628baff..685779b6 100644 --- a/common/autoboot.c +++ b/common/autoboot.c @@ -328,10 +328,11 @@ const char *bootdelay_process(void) int bootdelay; bootcount_inc(); - +/* s = env_get("bootdelay"); bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY; - +*/ +bootdelay = 0; if (IS_ENABLED(CONFIG_OF_CONTROL)) bootdelay = fdtdec_get_config_int(gd->fdt_blob, "bootdelay", bootdelay);
Comment out the function that reads uEnv.txt file.
Remove useless printed information.
Cropped Log
16:33:00:290 U-Boot SPL 2021.01-gd1345267-dirty (Jul 25 2023 - 16:14:18 +0800) 16:33:00:303 SYSFW ABI: 3.1 (firmware rev 0x0015 '21.5.1--w2022.07-am62x (Terrifi') 16:33:00:351 am625_init: board_init_f done(counter=1) 16:33:00:351 SPL initial stack usage: 13768 bytes 16:33:01:527 i2c_write: error waiting for data ACK (status=0x116) 16:33:01:527 i2c_write: error waiting for data ACK (status=0x116) 16:33:01:527 Auth Success! 16:33:01:544 normal mode 16:33:01:544 am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 16:33:01:544 Trying to boot from MMC1 16:33:01:729 Loading Environment from MMC... MMC: block number 0x3500 exceeds max(0x2000) 16:33:01:749 *** Warning - !read failed, using default environment 16:33:01:749 16:33:01:776 am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 16:33:01:795 am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 16:33:01:795 init_env from device 9 not supported! 16:33:01:795 Starting ATF on ARM64 core... 16:33:01:795 16:33:01:812 NOTICE: BL31: v2.5(release):v0.6-6-gd489c56b 16:33:01:812 NOTICE: BL31: Built : 15:08:18, Jun 26 2023 16:33:02:990 16:33:02:997 U-Boot SPL 2021.01-gd1345267-dirty (Jul 25 2023 - 16:14:43 +0800) 16:33:02:997 SYSFW ABI: 3.1 (firmware rev 0x0015 '21.5.1--w2022.07-am62x (Terrifi') 16:33:02:997 am625_init: board_init_f done 16:33:03:022 am625_init: spl_boot_device: devstat = 0x1843 bootmedia = 0x9 bootindex = 0 16:33:03:022 Trying to boot from MMC1 16:33:04:507 16:33:04:507 16:33:04:507 U-Boot 2021.01-gd1345267-dirty (Jul 25 2023 - 16:14:43 +0800) 16:33:04:507 16:33:04:507 SoC: AM62X SR1.0 16:33:04:508 Model: Forlinx OK62xx-C board 16:33:04:530 DRAM: 1 GiB 16:33:04:593 MMC: mmc@fa10000: 0, mmc@fa00000: 1 16:33:04:640 Loading Environment from MMC... OK 16:33:04:640 In: serial@2800000 16:33:04:640 Out: serial@2800000 16:33:04:640 Err: serial@2800000 16:33:04:654 51701 bytes read in 6 ms (8.2 MiB/s) 16:33:04:654 using kernel dtb display control 16:33:04:685 Saving Environment to MMC... Writing to MMC(0)... OK 16:33:04:701 Net: eth0: ethernet@8000000 16:33:04:701 Autoboot in 0 seconds 16:33:04:748 switch to partitions #0, OK 16:33:04:748 mmc0(part 0) is current device 16:33:04:795 SD/MMC found on device 0 16:33:05:104 3229642 bytes read in 141 ms (21.8 MiB/s) 16:33:05:228 20075008 bytes read in 111 ms (172.5 MiB/s) 16:33:05:228 51701 bytes read in 6 ms (8.2 MiB/s) 16:33:05:244 4575 bytes read in 5 ms (893.6 KiB/s) 16:33:05:285 ## Flattened Device Tree blob at 88000000 16:33:05:285 Booting using the fdt blob at 0x88000000 16:33:05:306 Loading Device Tree to 000000008fef0000, end 000000008fffffff ... OK 16:33:05:306 16:33:05:306 Starting kernel ...