gpiod无法检测部分引脚上升沿但sysfs可正常检测的问题

我正将基于sysfs的事件轮询上升沿检测实现升级为gpiod，以利用内核事件时间戳功能。测试中发现gpiod无法检测部分引脚的上升沿，通过命令行工具gpiomon验证后确认，该工具也只能检测到这些引脚的下降沿，但sysfs实现却能正常检测两种边沿。

环境信息 #

• 内核版本：v4.19.94-ti-r73
• libgpiod版本：v1.4.1
• 处理器：TI AM33xx
• 系统：Debian buster

设备树配置 #

设备树基于基础dtsi文件组合，并添加以下自定义配置：

&am33xx_pinmux {
    ecap0_pins_default: ecap0_pins_default {
        pinctrl-single,pins = <
            AM33XX_IOPAD(0x964, PIN_INPUT | MUX_MODE0) /* gpio0[7] */
        >;
    };
    gpio3_pins_default: gpio3_pins_default {
        pinctrl-single,pins = <
            AM33XX_IOPAD(0x99c, PIN_INPUT | MUX_MODE7) /* gpio3[17] */
        >;
    };
};

测试结果 #

gpiochip0引脚7测试 #

运行gpiomon gpiochip0 7可同时检测上升沿和下降沿：

gpiomon gpiochip0 7
event:  RISING EDGE offset: 7 timestamp: [1709072918.200972377]
event: FALLING EDGE offset: 7 timestamp: [1709072918.700979793]
event:  RISING EDGE offset: 7 timestamp: [1709072919.200997043]
event: FALLING EDGE offset: 7 timestamp: [1709072919.701002002]
event:  RISING EDGE offset: 7 timestamp: [1709072920.201015460]
event: FALLING EDGE offset: 7 timestamp: [1709072920.701029335]
event:  RISING EDGE offset: 7 timestamp: [1709072921.201066377]

gpiochip3引脚17测试 #

运行gpiomon gpiochip3 17仅能检测到下降沿：

gpiomon gpiochip3 17
event: FALLING EDGE offset: 17 timestamp: [1709073108.897098295]
event: FALLING EDGE offset: 17 timestamp: [1709073109.897153795]
event: FALLING EDGE offset: 17 timestamp: [1709073110.897172545]
event: FALLING EDGE offset: 17 timestamp: [1709073111.897198629]
event: FALLING EDGE offset: 17 timestamp: [1709073112.897222629]
event: FALLING EDGE offset: 17 timestamp: [1709073113.897253671]

GPIO调试信息 #

查看/sys/kernel/debug/gpio确认引脚已配置为IRQ：

gpiochip0: GPIOs 0-31, parent: platform/44e07000.gpio, gpio-0-31:
gpio-7   (ECAP0_IN_PWM0_OUT   |gpiomon             ) in  hi IRQ
gpiochip3: GPIOs 96-127, parent: platform/481ae000.gpio, gpio-96-127:
gpio-113 (MCASP0_AHCLKR       |gpiomon             ) in  lo IRQ

基于sysfs的监控工具可正常检测两个引脚的上升沿和下降沿。目前无法随意升级内核或软件版本，请问：为何gpiod无法检测部分引脚的上升沿却能检测下降沿？

内容的提问来源于stack exchange，提问作者Dan