内核日志

zcat /proc/config.gz | grep -E "CONFIG_SERIAL_QCOM_GENI"
# Expected:
# CONFIG_SERIAL_QCOM_GENI=y
# CONFIG_SERIAL_QCOM_GENI_CONSOLE=y

KERNEL_CMDLINE_EXTRA ?= "root=/dev/disk/by-partlabel/system rw rootwait \
                          console=ttyMSM0,115200n8 pcie_pme=nomsi earlycon"

Device UART header → USB-UART adapter → Host USB port

# Linux example
minicom -D /dev/ttyUSB0 -b 115200

earlycon

# Read current log level
cat /proc/sys/kernel/printk
# Example output: 7  4  1  7

# Set console log level to 4 (warnings and above only)
echo "4" > /proc/sys/kernel/printk

# Suppress all but emergencies (useful for release/performance tests)
echo "1" > /proc/sys/kernel/printk

loglevel=4      # warnings and above
quiet           # equivalent to loglevel=4 with reduced output
loglevel=0      # silence all output (only KERN_EMERG passes)

dmesg                         # full buffer
dmesg | head -50              # first 50 lines (early boot)
dmesg | tail -50              # most recent 50 lines
dmesg --level=err,warn        # errors and warnings only
dmesg -T                      # human-readable timestamps
dmesg -w                      # follow (like tail -f)

cat /proc/kmsg   # streams kernel log (Ctrl+C to stop)

journalctl -k           # kernel messages from the current boot
journalctl -k -b -1     # kernel messages from the previous boot

cat /var/log/kern.log    # Debian/Ubuntu style
cat /var/log/messages    # RHEL/embedded style

# Kernel command-line options (choose one):
quiet                    # suppress informational messages
console=null             # discard all console output
loglevel=0               # only KERN_EMERG messages pass

# CONFIG_SERIAL_EARLYCON is not set
# CONFIG_SERIAL_MSM_CONSOLE is not set

# Inside the kas shell
DEBUG_BUILD=1 bitbake qcom-multimedia-image

DEBUG_BUILD = "1"