Beaglebone devm_pwm_get returns ENODEV
Beaglebone devm_pwm_get returns ENODEV
我正在试验 Beaglebone black 的 pwm 驱动程序,基于 this one。
因为我将 Yocto 与 meta-bbb 层一起使用,所以我不得不重写 .dtsi:
&am33xx_pinmux {
bbb_pwm_P8_13_pins: bbb_pwm_P8_13_pins {
pinctrl-single,pins = <0x024 0x4>; /* P8_13 (ZCZ ball T10) | MODE 4 */
};
};
/ {
bbb-pwm@123 {
compatible = "tfe,bbb_pwm-1.00.a";
pwms = <&ehrpwm2 1 0 1>;
pwm-names = "PWM_P8_13";
pinctrl-names = "default";
pinctrl-0 = <&bbb_pwm_P8_13_pins>;
enabled = <0>;
duty = <0>;
status = "okay";
};
};
但是,在驱动程序探测功能期间,调用
pwm_test->pwm = devm_pwm_get(&pdev->dev, NULL);
returns ENODEV:
[ 7.538249] pinctrl-single 44e10800.pinmux: found group selector 15 for bbb_pwm_P8_13_pins
[ 7.538278] pinctrl-single 44e10800.pinmux: request pin 9 (44e10824.0) for bbb-pwm@123
[ 7.538291] pinctrl-single 44e10800.pinmux: enabling bbb_pwm_P8_13_pins function15
[ 7.538366] Loading bbb_pwm
[ 7.541304] bbb-pwm bbb-pwm@123: obtain a copy of previously claimed pinctrl
[ 7.541321] bbb-pwm bbb-pwm@123: Unable to request PWM (err = -19)
我发现错误代码是由 devm_pwm_get 的 sub-call 返回的:
static int pwm_device_request(struct pwm_device *pwm, const char *label)
{
/* .... */
if (!try_module_get(pwm->chip->ops->owner))
return -ENODEV;
/* ... */
}
但是,由于我是 Linux-驱动程序的新手,所以我不明白为什么会这样。有什么线索吗?
事实证明,内核中禁用了较低级别的 PWM 驱动程序 (EHRPWM)。在设备树中使用 menuconfig and ensuring that EHRPWM and EPWMSS 启用它解决了我的问题:
使用meta-bbb层,我只是通过bitbake访问了menuconfig:
bitbake virtual/kernel -c menuconfig
并加载位于 /meta-bbb/recipes-kernel/linux/linux-stable-4.4/beaglebone/defconfig
的 defconfig
我还在 local.conf
中添加了以下行
PREFERRED_VERSION_linux-stable = "4.4"
这是我的 dtsi:
&am33xx_pinmux {
bbb_pwm_P8_13_pins: bbb_pwm_P8_13_pins {
pinctrl-single,pins = <0x024 0x4>; /* P8_13 (ZCZ ball T10) | MODE 4 */
};
};
&ehrpwm2 {
status = "okay";
};
&epwmss2 {
status = "okay";
};
/ {
bbb-pwm@123 {
compatible = "tfe,bbb_pwm-1.00.a";
pwms = <&ehrpwm2 1 0 1>;
pwm-names = "PWM_P8_13";
pinctrl-names = "default";
pinctrl-0 = <&bbb_pwm_P8_13_pins>;
enabled = <0>;
duty = <0>;
status = "okay";
};
};
我正在试验 Beaglebone black 的 pwm 驱动程序,基于 this one。
因为我将 Yocto 与 meta-bbb 层一起使用,所以我不得不重写 .dtsi:
&am33xx_pinmux {
bbb_pwm_P8_13_pins: bbb_pwm_P8_13_pins {
pinctrl-single,pins = <0x024 0x4>; /* P8_13 (ZCZ ball T10) | MODE 4 */
};
};
/ {
bbb-pwm@123 {
compatible = "tfe,bbb_pwm-1.00.a";
pwms = <&ehrpwm2 1 0 1>;
pwm-names = "PWM_P8_13";
pinctrl-names = "default";
pinctrl-0 = <&bbb_pwm_P8_13_pins>;
enabled = <0>;
duty = <0>;
status = "okay";
};
};
但是,在驱动程序探测功能期间,调用
pwm_test->pwm = devm_pwm_get(&pdev->dev, NULL);
returns ENODEV:
[ 7.538249] pinctrl-single 44e10800.pinmux: found group selector 15 for bbb_pwm_P8_13_pins
[ 7.538278] pinctrl-single 44e10800.pinmux: request pin 9 (44e10824.0) for bbb-pwm@123
[ 7.538291] pinctrl-single 44e10800.pinmux: enabling bbb_pwm_P8_13_pins function15
[ 7.538366] Loading bbb_pwm
[ 7.541304] bbb-pwm bbb-pwm@123: obtain a copy of previously claimed pinctrl
[ 7.541321] bbb-pwm bbb-pwm@123: Unable to request PWM (err = -19)
我发现错误代码是由 devm_pwm_get 的 sub-call 返回的:
static int pwm_device_request(struct pwm_device *pwm, const char *label)
{
/* .... */
if (!try_module_get(pwm->chip->ops->owner))
return -ENODEV;
/* ... */
}
但是,由于我是 Linux-驱动程序的新手,所以我不明白为什么会这样。有什么线索吗?
事实证明,内核中禁用了较低级别的 PWM 驱动程序 (EHRPWM)。在设备树中使用 menuconfig and ensuring that EHRPWM and EPWMSS 启用它解决了我的问题:
使用meta-bbb层,我只是通过bitbake访问了menuconfig:
bitbake virtual/kernel -c menuconfig
并加载位于 /meta-bbb/recipes-kernel/linux/linux-stable-4.4/beaglebone/defconfig
的 defconfig我还在 local.conf
中添加了以下行PREFERRED_VERSION_linux-stable = "4.4"
这是我的 dtsi:
&am33xx_pinmux {
bbb_pwm_P8_13_pins: bbb_pwm_P8_13_pins {
pinctrl-single,pins = <0x024 0x4>; /* P8_13 (ZCZ ball T10) | MODE 4 */
};
};
&ehrpwm2 {
status = "okay";
};
&epwmss2 {
status = "okay";
};
/ {
bbb-pwm@123 {
compatible = "tfe,bbb_pwm-1.00.a";
pwms = <&ehrpwm2 1 0 1>;
pwm-names = "PWM_P8_13";
pinctrl-names = "default";
pinctrl-0 = <&bbb_pwm_P8_13_pins>;
enabled = <0>;
duty = <0>;
status = "okay";
};
};