u盘启动bootingfailed-(u盘启动booting不动了)

图5

系统启动后，可查看串口中断（131和132）：

root@xiaotianbsp:/# cat proc/interrupts CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 14: 0 0 0 0 0 0 GICv3 29 Edge arch_timer... 35: 16 0 0 0 0 0 GICv3 131 Level serial...222: 301 0 0 0 0 0 GICv3 132 Level debug...Err: 0

3.3、串口使能

配置文件：arch/arm64/boot/dts/rockchip/rockpi-4-linux.dtsi。

UART0 dts使能配置如下：

&uart0 { pinctrl-names = "default"; pinctrl-0 = <&uart0_xfer &uart0_cts>; status = "okay"; ## okay：打开串口功能; disabled:关闭该串口功能。};&uart2 { status = "okay"; ## 使能串口2};

注：

status = "okay"或"ok"，而不能用enable。

内核解析代码如下：

static bool __of_device_is_available(const struct device_node *device){ ... status = __of_get_property(device, "status", &statlen); ... if (statlen > 0) { if (!strcmp(status, "okay") || !strcmp(status, "ok")) return true; } return false;}

3.4、ttyFIQ0

系统使用/dev/ttyFIQ0作为console设备。

配置文件：arch/arm64/boot/dts/rockchip/rockpi-4-linux.dtsi，内容如下：

fiq_debugger: fiq-debugger { status = "disabled"; compatible = "rockchip,fiq-debugger"; rockchip,serial-id = <2>; ## 使用串口号(UART2),修改该属性的值，切换串口，同时切换串口的pinmux rockchip,signal-irq = <182>; rockchip,wake-irq = <0>; rockchip,irq-mode-enable = <1>; /* If enable uart uses irq instead of fiq */ rockchip,baudrate = <1500000>; /* Only 115200 and 1500000 */ pinctrl-names = "default"; pinctrl-0 = <&uart2c_xfer>; ## pinmux必须和serial-id对应 };

RockPI 4A单板使用的Debian系统，在配置文件extlinux.conf中设置console参数。

root@xiaotianbsp:/boot/extlinux# cat extlinux.conftimeout 10menu title select kernellabel kernel-4.4.154-90-rockchip-ga14f6502e045 kernel /vmlinuz-4.4.154-90-rockchip-ga14f6502e045 devicetreedir /dtbs/4.4.154-90-rockchip-ga14f6502e045 ## 使能early printk，ttyFIQ0做为console设备，串口波特率1.5M，8个数据位，1个停止位 append earlyprintk console=ttyFIQ0,1500000n8 init=/sbin/init root=PARTUUID=b921b045-1d rw rootwait rootfstype=ext4

系统启动后，可通过cmdline查看。

root@xiaotianbsp:~# cat /proc/cmdlineearlyprintk console=ttyFIQ0,1500000n8 init=/sbin/init root=PARTUUID=b921b045-1d rw rootwait rootfstype=ext4四、UART驱动

RK3399 Linux4.4内核UART驱动采用8250通用驱动，类型是16550A。主要实现文件：

drivers/tty/serial/8250/8250_dma.c ## UART dma实现drivers/tty/serial/8250/8250_dw.c ## Synopsys DesignWare 8250串口驱动drivers/tty/serial/8250/8250_early.c ## early console实现drivers/tty/serial/8250/8250_port.c ## UART端口配置的相关接口

UART驱动和调试后续介绍。

在嵌入式Linux系统中，最常见的就是使用串口输出内核日志进行功能调试。

5.1、printk

在Linux内核中，可用函数printk()将内核信息输出到内核信息缓冲区中。

内核日志输出分不同的等级，定义文件：include/linux/kern_levels.h，包括：

#define LOGLEVEL_EMERG 0 /* system is unusable */#define LOGLEVEL_ALERT 1 /* action must be taken immediately */#define LOGLEVEL_CRIT 2 /* critical conditions */#define LOGLEVEL_ERR 3 /* error conditions */#define LOGLEVEL_WARNING 4 /* warning conditions */#define LOGLEVEL_NOTICE 5 /* normal but significant condition */#define LOGLEVEL_INFO 6 /* informational */#define LOGLEVEL_DEBUG 7 /* debug-level messages */

除printk()函数外，还可以使用pr_**()和dev_**()。

pr_**定义文件：include/linux/printk.h，宏定义如下：

#define pr_emerg(fmt, ...) \ printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__)#define pr_alert(fmt, ...) \ printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)#define pr_crit(fmt, ...) \ printk(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__)#define pr_err(fmt, ...) \ printk(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)#define pr_warning(fmt, ...) \ printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)#define pr_warn pr_warning#define pr_notice(fmt, ...) \ printk(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__)#define pr_info(fmt, ...) \ printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)

dev_**定义文件：drivers/base/core.c，函数定义如下：

#define define_dev_printk_level(func, kern_level) \void func(const struct device *dev, const char *fmt, ...) \{ \ struct va_format vaf; \ va_list args; \ \ va_start(args, fmt); \ \ vaf.fmt = fmt; \ vaf.va = &args; \ \ __dev_printk(kern_level, dev, &vaf); \ \ va_end(args); \} \EXPORT_SYMBOL(func);define_dev_printk_level(dev_emerg, KERN_EMERG);define_dev_printk_level(dev_alert, KERN_ALERT);define_dev_printk_level(dev_crit, KERN_CRIT);define_dev_printk_level(dev_err, KERN_ERR);define_dev_printk_level(dev_warn, KERN_WARNING);define_dev_printk_level(dev_notice, KERN_NOTICE);define_dev_printk_level(_dev_info, KERN_INFO);

5.1.1、日志输出等级

通过修改loglevel或/proc/sys/kernel/printk的值可以调整内核日志输出等级。

在系统启动前，通过配置loglevel，可以调整串口日志输出等。

root@xiaotianbsp:~# cat /boot/extlinux/extlinux.conf...label kernel-debug kernel /debug/Image fdt /debug/rk3399-rock-pi-4a.dtb ## 修改loglevel调整串口输出日志等级 append earlyprintk console=ttyFIQ0,1500000n8 loglevel=4 init=/sbin/init root=PARTUUID=b921b045-1d rw rootwait rootfstype=ext4 no_console_suspend initcall_debug

其他系统（如：Ubuntun、Buildroot或Android），一般在bootargs中修改loglevel。

注：

no_console_suspend用于Linux系统电源管理调试，表示系统休眠（suspend）后，串口不休眠，仍可输出。

在系统启动后，也可动态调整串口日志输出等级。

root@xiaotianbsp:/proc/sys/kernel# cat printk7 4 1 7root@xiaotianbsp:/proc/sys/kernel# echo 4 > printkroot@xiaotianbsp:/proc/sys/kernel# cat printk4 4 1 7

printk中的数字对应不同的日志级别，只要修改console口的日志级别即可。

int console_printk[4] = { CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */ ## 控制台的日志级别 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */ ## 默认消息日志级别 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */ ## 最小控制台日志级别 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */ ## 默认控制台日志级别};

5.1.2、日志时间戳

在系统启动后，可以动态调整内核日志时间戳的显示。

## 1.time值为Y，表示显示时间戳root@xiaotianbsp:/# cat /sys/module/printk/parameters/timeY## 2.此时日志显示有时间戳root@xiaotianbsp:/# find . -name time[ 1719.836194] FAT-fs (sda4): error, invalid access to FAT (entry 0x07b03538)[ 1719.836874] FAT-fs (sda4): error, invalid access to FAT (entry 0x07b03538) ## 3.设置time值为Nroot@xiaotianbsp:/# echo N > /sys/module/printk/parameters/time## 4.此时日志显示有时间戳root@xiaotianbsp:/# find . -name timeFAT-fs (sda4): error, invalid access to FAT (entry 0x07b03538)FAT-fs (sda4): error, invalid access to FAT (entry 0x07b03538)

5.2、dmesg

在系统启动后，如果已经错过内核启动阶段或使用非串口（例：adb/ssh登录）连接调试板，可以使用dmesg查看内核日志。

dmesg用法如下：

root@xiaotianbsp:/# dmesg -hUsage: dmesg [options]Display or control the kernel ring buffer.Options: -C, --clear clear the kernel ring buffer -c, --read-clear read and clear all messages -D, --console-off disable printing messages to console -E, --console-on enable printing messages to console -F, --file <file> use the file instead of the kernel log buffer -f, --facility <list> restrict output to defined facilities -H, --human human readable output -k, --kernel display kernel messages -L, --color[=<when>] colorize messages (auto, always or never) colors are enabled by default -l, --level <list> restrict output to defined levels -n, --console-level <level> set level of messages printed to console -P, --nopager do not pipe output into a pager -r, --raw print the raw message buffer -S, --syslog force to use syslog(2) rather than /dev/kmsg -s, --buffer-size <size> buffer size to query the kernel ring buffer -u, --userspace display userspace messages -w, --follow wait for new messages -x, --decode decode facility and level to readable string -d, --show-delta show time delta between printed messages -e, --reltime show local time and time delta in readable format -T, --ctime show human-readable timestamp (may be inaccurate!) -t, --notime don't show any timestamp with messages --time-format <format> show timestamp using the given format: [delta|reltime|ctime|notime|iso]Suspending/resume will make ctime and iso timestamps inaccurate. -h, --help display this help and exit -V, --version output version information and exitSupported log facilities: kern - kernel messages user - random user-level messages mail - mail system daemon - system daemons auth - security/authorization messages syslog - messages generated internally by syslogd lpr - line printer subsystem news - network news subsystemSupported log levels (priorities): emerg - system is unusable alert - action must be taken immediately crit - critical conditions err - error conditions warn - warning conditions notice - normal but significant condition info - informational debug - debug-level messagesFor more details see dmesg(1).

5.2.1、显示内核日志

root@xiaotianbsp:/# dmesg[ 0.000000] Booting Linux on physical CPU 0x0[ 0.000000] Initializing cgroup subsys cpuset[ 0.000000] Initializing cgroup subsys cpu[ 0.000000] Initializing cgroup subsys cpuacct[ 0.000000] Linux version 4.4.154-90-rockchip-ga14f6502e045 (root@2705a206000b) (gcc version 7.3.1 20180425 [linaro-7.3-2018.05 revision d29120a424ecfbc167ef90065c0eeb7f91977701] (Linaro GCC 7.3-2018.05) ) #22 SMP Tue Jul 30 10:32:28 UTC 2019

5.2.2、限制日志输出等级

## 仅输出error信息root@xiaotianbsp:/# dmesg -l err[ 2.170152] rockchip-pcie f8000000.pcie: PCIe link training gen1 timeout![ 2.175658] rk-vcodec ff650000.vpu_service: could not find power_model node[ 2.180010] rk-vcodec ff660000.rkvdec: could not find power_model node[ 2.200359] rockchip-vop ff900000.vop: missing rockchip,grf property[ 2.201913] rockchip-vop ff8f0000.vop: missing rockchip,grf property[ 2.203632] i2c i2c-9: of_i2c: modalias failure on /hdmi@ff940000/ports[ 2.240381] mali ff9a0000.gpu: Failed to get regulator[ 2.240839] mali ff9a0000.gpu: Power control initialization failed[ 2.260317] rk_gmac-dwmac fe300000.ethernet: cannot get clock clk_mac_speed

## 同时输出error和warning信息root@xiaotianbsp:/# dmesg -l err,warn[ 0.000000] rockchip_clk_register_frac_branch: could not find dclk_vop0_frac as parent of dclk_vop0, rate changes may not work[ 0.000000] rockchip_clk_register_frac_branch: could not find dclk_vop1_frac as parent of dclk_vop1, rate changes may not work[ 0.000000] rockchip_cpuclk_pre_rate_change: limiting alt-divider 33 to 31[ 1.589058] thermal thermal_zone1: power_allocator: sustainable_power will be estimated[ 1.637902] phy phy-ff770000.syscon:usb2-phy@e450.1: Failed to get VBUS supply regulator[ 1.639962] phy phy-ff770000.syscon:usb2-phy@e460.3: Failed to get VBUS supply regulator[ 2.170152] rockchip-pcie f8000000.pcie: PCIe link training gen1 timeout!

5.2.3、查找某条信息

root@xiaotianbsp:~# dmesg | grep 电脑rockchip-vop[ 2.197270] rockchip-vop ff900000.vop: missing rockchip,grf property[ 2.198853] rockchip-vop ff8f0000.vop: missing rockchip,grf propertyroot@xiaotianbsp:~# dmesg | grep xiaotianbsproot@xiaotianbsp:~#

5.2.4、清空环形缓冲区信息

root@xiaotianbsp:/# dmesg -c[ 0.000000] Booting Linux on physical CPU 0x0[ 0.000000] Initializing cgroup subsys cpuset[ 0.000000] Initializing cgroup subsys cpu[ 0.000000] Initializing cgroup subsys cpuacct...root@xiaotianbsp:/# dmesgroot@xiaotianbsp:/#

dmesg更多用法大家可以自行测试。

注：转载请注明作者和出处。