一，前言

资源就的利用起来。linux下串口raw驱动(US100超声波)--Apple的学习笔记已经用US100玩了串口，US100还可以用GPIO和中断来玩。原理就是triq发送大于10us的高电平，然后echo脚就会回复高电平，高电平的维持时间，就代表了障碍物的距离。我之前用过gpio但是是老的API，所以本次的其中一个目标很清晰，就是用新的gpiod的API，那么头文件从 #include 要改成 #include 了。另外我对中断其实用的少，正好本次有机会用下，将来再详细了解。过程中觉得延时10us占用cpu而且不准，所以改成pwm来输出10us非常准。这个US100还比较有的玩，将来我还会再玩一次，重新设计驱动，并且将参数都设计到设备树中。工程已经上传我的gitee，见工程14。

二，设备树修改

依然使用上一篇博客的uart引脚，但是mode设置为7，设置为GPIO，然后设备树设置中断为both边缘触发。

ussensor_pins: pinmux_ussensor_pins {

pinctrl-single,pins = <

AM33XX_PADCONF(AM335X_PIN_UART1_RXD, PIN_INPUT_PULLUP, MUX_MODE7) //Echo:gpio0.14

AM33XX_PADCONF(AM335X_PIN_UART1_TXD, PIN_OUTPUT_PULLDOWN, MUX_MODE7) //Triq :gpio0.15

>;

};

ussensor:ussensor0 {

compatible = "applecai,AppleUS100";

interrupt-parent = ;

interrupts = <14 IRQ_TYPE_EDGE_BOTH>; /* input pin:gpio0.14 raise and falling*/

echo-gpios = ; /* input pin */

triq-gpios = ; /* output pin */

pinctrl-names = "default";

pinctrl-0 = ;

status = "okay";

};

三，遇到的问题

insmod产生bt。

对于不复杂的驱动，我倾向于使用misc。而misc的.name没有添加。导致bt。

us2运行第二次后，产生bt

原因request_irq后，free_irq的devid参数传的不正确。后来直接用devm_request_irq就不用free了。另外irqflag参数我之前理解为填写边缘触发等，但是看了源码后才知道理解错误，参考其它driver，我这里改成了shared中断。

[ 38.242019] us100 device id is 10485820

[ 40.143138] genirq: Flags mismatch irq 61. 00000003 (us100-echo-gpio) vs. 00000003 (us100-echo-gpio)

[ 40.156380] ------------[ cut here ]------------

[ 40.161045] WARNING: CPU: 0 PID: 119 at kernel/irq/manage.c:1737 __free_irq+0xc0/0x330

[ 40.168996] Trying to free already-free IRQ 61

[ 40.173457] Modules linked in: US100_drv(O) [last unloaded: US100_drv]

[ 40.180028] CPU: 0 PID: 119 Comm: us2 Tainted: G O 5.4.61 #39

[ 40.187105] Hardware name: Generic AM33XX (Flattened Device Tree)

[ 40.193224] Backtrace:

[ 40.195694] [] (dump_backtrace) from [] (show_stack+0x20/0x24)

[ 40.203300] r7:00000000 r6:60070093 r5:00000000 r4:c0ebd85c

[ 40.208991] [] (show_stack) from [] (dump_stack+0xe8/0x120)

[ 40.216344] [] (dump_stack) from [] (__warn+0xd0/0x108)

[ 40.223340] r10:60070013 r9:c0b255b4 r8:c0e05148 r7:000006c9 r6:00000009 r5:c01a9328

[ 40.231203] r4:c0b2551c r3:00000000

[ 40.234797] [] (__warn) from [] (warn_slowpath_fmt+0x9c/0xc0)

[ 40.242315] r7:00000009 r6:c01a9328 r5:000006c9 r4:c0b2551c

[ 40.248002] [] (warn_slowpath_fmt) from [] (__free_irq+0xc0/0x330)

[ 40.255956] r9:0000003d r8:dd03e0d0 r7:dd03e068 r6:00000000 r5:dd03e000 r4:00000000

[ 40.263734] [] (__free_irq) from [] (free_irq+0x48/0xa8)

[ 40.270816] r10:bf0011c4 r9:c0e9c220 r8:dd25f5d0 r7:dd20e900 r6:00000000 r5:dd03e000

[ 40.278678] r4:00000000

[ 40.281235] [] (free_irq) from [] (AppleUS100_open+0x60/0x94 [US100_drv])

[ 40.289798] r7:dd20e900 r6:c0e9c234 r5:fffffff0 r4:bf0022c0

[ 40.295488] [] (AppleUS100_open [US100_drv]) from [] (misc_open+0x124/0x17c)

[ 40.304310] r5:0000003c r4:bf002000

[ 40.307911] [] (misc_open) from [] (chrdev_open+0xe8/0x1bc)

[ 40.315255] r10:00000000 r9:00000000 r8:dd20e900 r7:c0e05148 r6:dd25f5d0 r5:c0a5c750

[ 40.323117] r4:de298880 r3:c06563a0

[ 40.326719] [] (chrdev_open) from [] (do_dentry_open+0x134/0x414)

[ 40.334586] r10:dd20e900 r9:00000000 r8:c02f56c8 r7:dd20e908 r6:dd25f5d0 r5:00000000

[ 40.342447] r4:dd20e900

[ 40.344997] [] (do_dentry_open) from [] (vfs_open+0x3c/0x40)

[ 40.352428] r9:00000000 r8:00000000 r7:00000002 r6:00000000 r5:00000000 r4:dd31fe90

[ 40.360211] [] (vfs_open) from [] (path_openat+0x2b4/0x13e0)

[ 40.367642] [] (path_openat) from [] (do_filp_open+0x80/0xec)

[ 40.375160] r10:00000142 r9:dd31e000 r8:00000001 r7:c0e05148 r6:dd31ff50 r5:dd31fe90

[ 40.383023] r4:00000003

[ 40.385571] [] (do_filp_open) from [] (do_sys_open+0x168/0x218)

[ 40.393263] r8:fffff000 r7:de113000 r6:ffffff9c r5:c0e05148 r4:00000003

[ 40.399997] [] (do_sys_open) from [] (sys_openat+0x1c/0x20)

[ 40.407341] r10:00000142 r9:dd31e000 r8:c01011c4 r7:00000142 r6:00085460 r5:00010134

[ 40.415202] r4:00010c30

[ 40.417752] [] (sys_openat) from [] (ret_fast_syscall+0x0/0x28)

[ 40.425441] Exception stack(0xdd31ffa8 to 0xdd31fff0)

[ 40.430518] ffa0: 00010c30 00010134 ffffff9c 0005e160 00000000 00000000

[ 40.438736] ffc0: 00010c30 00010134 00085460 00000142 00000000 00000000 00000000 be9c6d24

[ 40.446950] ffe0: 000858b0 be9c6ce0 000104d0 00027a14

[ 40.452022] ---[ end trace 16d04ba7b422cf72 ]---

/dev/AppleUS100: Device or resource busy

gpio初始化引脚不正确

devm_gpiod_get_optional的第3个参数可以在请求引脚的同时设置电平和方向。一开始不知道，写的是0，所以insmod后不正确。

中断thread下半部进入不了.

中断上半部return的参数不对。

时间采集不准。

采集时间放入上半部后相对正确。

采集时间差偏小

参见如下第七和第八章节的测试。暂时原因未知，猜测为ktime不准。事后网上搜索下了下有用hrtimer是高精度的。将来有机会再了解下原理适用下。

四，第一步驱动加载及probe测试成功

查看设备号

# cd /sys/class/misc/

# ls

AppleUS100 loop-control vga_arbiter

cpu_dma_latency ubi_ctrl

# cd AppleUS100/

# ls

dev power subsystem uevent

# cat dev

10:60

查看驱动

# ls -al

total 0

drwxr-xr-x 3 root root 0 Jan 1 00:03 .

drwxr-xr-x 21 root root 0 Jan 1 00:03 ..

lrwxrwxrwx 1 root root 0 Jan 1 00:03 driver -> ../../../bus/platform/drivers/appleUS100

-rw-r--r-- 1 root root 4096 Jan 1 00:03 driver_override

-r--r--r-- 1 root root 4096 Jan 1 00:03 modalias

lrwxrwxrwx 1 root root 0 Jan 1 00:03 of_node -> ../../../firmware/devicetree/base/ussensor0

drwxr-xr-x 2 root root 0 Jan 1 00:03 power

lrwxrwxrwx 1 root root 0 Jan 1 00:03 subsystem -> ../../../bus/platform

-rw-r--r-- 1 root root 4096 Jan 1 00:03 uevent

驱动框架，irq识别正确，APP open和close正常

# insmod US100_drv.ko

[ 101.155869] irq num is 61

[ 139.464344] us100 probe!

[ 139.469573] appleUS100 ussensor0: GPIO lookup for consumer triq

[ 139.475713] appleUS100 ussensor0: using device tree for GPIO lookup

[ 139.482121] of_get_named_gpiod_flags: parsed 'triq-gpios' property of node '/ussensor0[0]' - status (0)

[ 139.491590] gpio gpiochip0: Persistence not supported for GPIO 15

[ 139.497749] no flags found for triq

[ 139.501265] miscUS100_dev.cmdpin is 15

[ 139.501273] appleUS100 ussensor0: GPIO lookup for consumer echo

[ 139.511012] appleUS100 ussensor0: using device tree for GPIO lookup

[ 139.517374] of_get_named_gpiod_flags: parsed 'echo-gpios' property of node '/ussensor0[0]' - status (0)

[ 139.526854] gpio gpiochip0: Persistence not supported for GPIO 14

[ 139.533002] no flags found for echo

[ 139.536513] miscUS100_dev.echopin is 14

# ./us2

[ 139.539789] us100 device id min is 60

ok

# ./us2

[ 141.592831] irq num is 61

ok

^C

# ./us2

[ 147.848742] irq num is 61

ok

# cat /proc/interrupts

CPU0

16: 1626 INTC 68 Level gp_timer

18: 0 INTC 3 Level arm-pmu

19: 8 INTC 12 Level 49000000.edma_ccint

21: 0 INTC 14 Level 49000000.edma_ccerrint

28: 0 INTC 96 Level 44e07000.gpio

29: 313 INTC 72 Level 44e09000.serial

30: 146 INTC 70 Level 44e0b000.i2c

42: 0 INTC 98 Level 4804c000.gpio

43: 37 INTC 64 Level mmc0

45: 0 INTC 30 Level 4819c000.i2c

46: 0 INTC 32 Level 481ac000.gpio

47: 0 INTC 62 Level 481ae000.gpio

48: 46 INTC 28 Level mmc1

52: 1273 INTC 41 Level 4a100000.ethernet

53: 763 INTC 42 Level 4a100000.ethernet

56: 0 44e07000.gpio 6 Edge 48060000.mmc cd

57: 0 INTC 7 Level tps65217-irq

IPI0: 0 CPU wakeup interrupts

IPI1: 0 Timer broadcast interrupts

IPI2: 0 Rescheduling interrupts

IPI3: 0 Function call interrupts

IPI4: 0 CPU stop interrupts

IPI5: 0 IRQ work interrupts

IPI6: 0 completion interrupts

Err: 0

# rmmod US100_drv.ko

五，GPIO引脚控制测试通过

在框架中的open添加了GPIOD及申请IRQ的代码，在read函数中添加控制triq引脚电平及延时10us。示波器测试通过，并且echo脚有正确的返回。

# insmod US100_drv1.ko

[ 322.604133] irq num is 61

[ 384.515868] us100 probe!

[ 384.521094] appleUS100 ussensor0: GPIO lookup for consumer triq

[ 384.527249] appleUS100 ussensor0: using device tree for GPIO lookup

[ 384.533660] of_get_named_gpiod_flags: parsed 'triq-gpios' property of node '/ussensor0[0]' - status (0)

[ 384.543162] gpio gpiochip0: Persistence not supported for GPIO 15

[ 384.549298] miscUS100_dev.cmdpin is 15

[ 384.549307] appleUS100 ussensor0: GPIO lookup for consumer echo

[ 384.559046] appleUS100 ussensor0: using device tree for GPIO lookup

[ 384.565426] of_get_named_gpiod_flags: parsed 'echo-gpios' property of node '/ussensor0[0]' - status (0)

[ 384.574912] gpio gpiochip0: Persistence not supported for GPIO 14

[ 384.581043] miscUS100_dev.echopin is 14

# ./us2

[ 384.584160] us100 device id min is 60

ok

# ./us2

[ 390.780167] irq num is 61

ok

image.png

六，将10us的高电平有io控制改为PWM控制通过

用pwm控制就非常准。

image.png

七，用示波器来验证时间差，时间差偏小。

# ./us2

ok

[ 417.304899] last is 417302210883,now is 417302621549,dis:410666

[ 417.307555] dis:69

distance is 69

410666ns，但是示波器显示为424us

image.png

八，用ftrace验证时间差

ftrace硬中断上半部会进入2次，时间差为58.201850-58.200688=1162us。ktime记录的时间为ns，一个为58198435298，另外一个为58199583631，差值为1148us。也说明ktime函数偏小。

# insmod US100_drv6.ko

[ 19.069904] US100_drv6: loading out-of-tree module taints kernel.

[ 19.078024] us100 probe!

[ 19.080617] appleUS100 ussensor0: GPIO lookup for consumer triq

[ 19.086760] appleUS100 ussensor0: using device tree for GPIO lookup

[ 19.093172] of_get_named_gpiod_flags: parsed 'triq-gpios' property of node '/ussensor0[0]' - status (0)

[ 19.102676] gpio gpiochip0: Persistence not supported for GPIO 15

[ 19.108812] miscUS100_dev.cmdpin is 15

[ 19.108822] appleUS100 ussensor0: GPIO lookup for consumer echo

[ 19.118563] appleUS100 ussensor0: using device tree for GPIO lookup

[ 19.124945] of_get_named_gpiod_flags: parsed 'echo-gpios' property of node '/ussensor0[0]' - status (0)

[ 19.134430] gpio gpiochip0: Persistence not supported for GPIO 14

[ 19.140561] miscUS100_dev.echopin is 14

# mount -t debugfs nodev /sys/kernel/debug

# cd /sys/kernel/debug/tracing

# echo 0 > tracing_on

# echo us100_irq_handler > set_ftrace_filter

# echo function > current_tracer

# echo 1 > tracing_on

# cd /usr/study/

# ./us2

ok

[ 19.142810] us100 device id min is 60

[ 58.201906] last is 58198435298,now is 58199583631,dis:1148333

distance is 195

# cd /sys/kernel/debug/tracing

# cat trace | head -20

# tracer: function

#

# entries-in-buffer/entries-written: 2/2 #P:1

#

# _-----=> irqs-off

# / _----=> need-resched

# | / _---=> hardirq/softirq

# || / _--=> preempt-depth

# ||| / delay

# TASK-PID CPU# |||| TIMESTAMP FUNCTION

# | | | |||| | |

-0 [000] d.h. 58.200688: us100_irq_handler

-0 [000] d.h. 58.201850: us100_irq_handler

九，多进程验证

今天在昨天的基础上将自定义的设备结构体从全局变量，改成了通过指针传递，然后在open函数通过struct miscUS100 *dev = container_of(filp->private_data,struct miscUS100, miscdev);来获取，依然放入工程14，文件名为US100_drv8.c。并且添加了锁，当一个进程打开文件处理后，其它进程不能打开此文件。测试通过。

Welcome to Buildroot

buildroot login: root

# cd /usr/study/

# insmod US100_drv8.ko

[ 13.282705] US100_drv8: loading out-of-tree module taints kernel.

[ 13.290724] appleUS100 ussensor0: GPIO lookup for consumer echo

[ 13.296902] appleUS100 ussensor0: using device tree for GPIO lookup

[ 13.303306] of_get_named_gpiod_flags: parsed 'echo-gpios' property of node '/ussensor0[0]' - status (0)

[ 13.312806] gpio gpiochip0: Persistence not supported for GPIO 14

# ./us2

[ 13.318939] miscUS100_dev.echopin is 14

[ 14.755360] appleUS100 ussensor0: irq num is 61

[ 14.772369] appleUS100 ussensor0: last is 14768965835,now is 14770115335,dis:1149500

distance is 195

# ./us2 &

# [ 22.226804] appleUS100 ussensor0: irq num is 61

[ 22.291166] appleUS100 ussensor0: last is 22288684127,now is 22288873502,dis:189375

distance is 32

./us2

[ 23.939970] US100 is busy

/dev/AppleUS100: Device or resource busy

# ./us2

[ 25.143762] US100 is busy

/dev/AppleUS100: Device or resource busy

# ./us2

[ 27.298167] US100 is busy

/dev/AppleUS100: Device or resource busy

[1]+ Done ./us2

# ./us2

[ 32.293119] appleUS100 ussensor0: irq num is 61

[ 32.358104] appleUS100 ussensor0: last is 32355629628,now is 32355829503,dis:199875

distance is 33

^C

# ./us2

[ 36.579675] appleUS100 ussensor0: irq num is 61

[ 36.644860] appleUS100 ussensor0: last is 36642381796,now is 36642584587,dis:202791

distance is 34

^C

# ./us2

[ 39.601888] appleUS100 ussensor0: irq num is 61

[ 39.667097] appleUS100 ussensor0: last is 39664613254,now is 39664820879,dis:207625

distance is 35