OK6410A development board (three) 27 u-boot-2021.01 boot analysis U-boot image running part console

The console has nothing to do with input, only with output

Model

Both the serial port and LCD can be used as output, so it can be used as a console

Output without console mechanism: Serial port

Just use serial_puts to print information to the serial port

Output without console mechanism: lcd

Just use lcd_puts to print information to the LCD

console

Register serial_puts and lcd_puts to the console mechanism

Call console_puts provided by console to print information

Whether to print to the serial port or LCD depends on the configuration of the console.

How does U-boot handle this?

Before board_init_f->console_init_f

gd->have_console is 0

The serial port is also initialized

No output can be done at this time (printf is usually called for output). The information output by printf is in memory.

After board_init_f->console_init_f, before board_init_r->console_init_r

gd->have_console is now 1

gd->flags & GD_FLG_DEVINIT == 0

The serial port has been initialized

The information previously output in the memory has been printed to the serial port

At this time, the information output by printf is on the serial port, and serial_puts is called.

After board_init_r->console_init_r

gd->have_console is now 1

gd->flags & GD_FLG_DEVINIT == 1

The serial port has been initialized and registered (init_sequence_r->stdio_add_devices->drv_system_init->stdio_register) to the console system

The lcd has been initialized and registered (init_sequence_r->stdio_add_devices->drv_lcd_init->stdio_register) to the console system

At this time, the output can be output (the output usually calls printf)

At this time, the information output by printf may be output to the LCD or serial port according to the settings, and console_puts is called

console_puts then calls serial_puts or lcd_puts

Details stage

stdio_register

In fact, it is to mount the struct stdio_dev structure to the end of the global variable static struct stdio_dev devs;

console_init_r

console_init_r has two implementations depending on whether SYS_CONSOLE_IS_IN_ENV is defined

SYS_CONSOLE_IS_IN_ENV // Y if CONSOLE_MUX is Y

This allows multiple input/output devices to be set up at boot time.

For example, if stdout is set to "serial,video" then output will be sent to both the serial and video devices at boot time.

Environment variables can be updated after boot to change input/output devices.

CONSOLE_MUX // VIDEO/DM_VIDEO/LCD is Y, then Y

This allows the use of multiple devices per console "file".

For example, stdout can be set to go to both serial and video.

Similarly, stdin can be set to come from both serial and keyboard.

Input can be provided from any source.

Console multiplexing adds a small amount of size to U-Boot.

Changes to the environment variables stdout, stdin, and stderr take effect immediately.

console_init_r SYS_CONSOLE_IS_IN_ENV when defined

// Problem: outputdev is found, but how to use outputdev in printf

console_init_r

stdinname = env_get("stdin");

stdoutname = env_get("stdout");

// stdoutname can be lcd,serial0@7F005000

// can be lcd

// can be serial0@7F005000

// If there is a comma (,) it means there are two stdout devices

stderrname = env_get("stderr");

iomux_err = iomux_doenv(stdin, stdinname);

iomux_err += iomux_doenv(stdout, stdoutname); 

for_each_consoledevice

console_devices[console] = (struct stdio_dev **)realloc(console_devices[console], cs_idx * sizeof(struct stdio_dev *));

memcpy(console_devices[console], cons_set, cs_idx * sizeof(struct stdio_dev *));

cd_count[console] = cs_idx;

iomux_err += iomux_doenv(stderr, stderrname);

stdio_print_current_devices

gd->flags |= GD_FLG_DEVINIT;

print_pre_console_buffer(flushpoint);

console_init_r SYS_CONSOLE_IS_IN_ENV is not defined

consumer

console_puts

for (i = 0; i < cd_count[file]; i++)

dev = console_devices[file][i];

dev->puts(dev, s);

Console Settings

Correct Setup

Set the environment variables in the u-boot environment to output on the LCD

Only LCD output // When set like this, the serial port also has output, because the program has been modified 8c24d5adfbc43826246716e41f964f0467c1cfd6

// BUG at this time: some miscellaneous data (promot data) will come out on the serial port

env set stdout lcd

s

Only serial output

// No problems at this time

env set stdout serial0@7F005000

s

Both output // When set like this, the serial port prints twice because the program has been modified 8c24d5adfbc43826246716e41f964f0467c1cfd6

// The timing is not satisfied at this time (because the LCD needs to be written immediately after getc from the serial port, and the next character cannot be getc from the serial port at this time)

env set stdout "lcd,serial0@7F005000" // Every time printf/puts is executed, output from lcd first

env set stdout "serial0@7F005000,lcd" // Every time printf/puts is executed, output from serial first

s

Wrong settings

env set stdout bbb

## Error inserting "stdout" variable, errno=22

bbb is not a stdout device and cannot be set like this

env set stdout parsing

It must be something like iomux_doenv

//TODO