设置没有 pinctrl-names 的设备树节点时，GPIO 不受控制

编程问答 2022-05-28

问题描述

我正在研究 imx8mm 并使用 Linux 内核 v4.14.98 测试 GPIO。

设备树节点为：

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URL: https://url/dataset/dataset1/resource/0797383e-bac0-4114-943b-87c74d2677a9
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TimeoutError: QueuePool limit of size 5 overflow 10 reached,timeout 30

我写了一个驱动程序来测试这个

&iomuxc {
    pinctrl-names = "default";
    
    ...

    imx8mm-evk {    
        pinctrl_gpio_plural: gpiopluralgrp {
            fsl,pins = <
                MX8MM_IOMUXC_GPIO1_IO11_GPIO1_IO11      0x41
            >;
        };
    };
};

...

plural {
    compatible = "gpio-plural";
    /* pinctrl-names = "default"; */   
    pinctrl-0 = <&pinctrl_gpio_plural>;
    reset-gpios = <&gpio1 11 GPIO_ACTIVE_HIGH>;
};

但是，当我将 pinctrl-names 注释为上面显示的设备树时，我无法控制 GPIO 引脚。 GPIO 引脚始终保持高电平。

在 devicetree.c 中，static int gpio_plural_probe(struct platform_device *pdev) { struct gpio_plural_data *drvdata; drvdata = devm_kzalloc(&pdev->dev,sizeof(*drvdata),GFP_KERNEL); if (drvdata == NULL) return -ENOMEM; drvdata->reset = devm_gpiod_get(&pdev->dev,"reset",GPIOD_OUT_HIGH); if (IS_ERR(drvdata->reset)) { printk("Error: reset not found\n"); return -EINVAL; } gpiod_set_value(drvdata->reset,0); mdelay(100); gpiod_set_value(drvdata->reset,1); mdelay(100); gpiod_set_value(drvdata->reset,1); return 0; } 将替换为 statename 后缀，此处为“0”。但它只是一个常量名称，可以是任何字符串。所以我的问题是为什么我不能在不设置 pinctrl-names 的情况下控制 GPIO 引脚？

解决方法

它不能是任何名称，大多数节点都会有 pinctrl-names = "default";，因为这使 pinctrl-0 成为设备引脚的默认状态。

这实际上非常重要，因为设备核心将在探测设备之前使用它来检索和设置正确的状态，请参阅pinctrl_bind_pins。它确实：

dev->pins->default_state = pinctrl_lookup_state(dev->pins->p,PINCTRL_STATE_DEFAULT);

其中 PINCTRL_STATE_DEFAULT 是 "default"。

然后，它选择状态：

ret = pinctrl_select_state(dev->pins->p,dev->pins->init_state);

如果您不想使用 default 名称，则必须在驱动程序中选择正确的状态。

其他通用状态名称是：

#define PINCTRL_STATE_DEFAULT "default"
#define PINCTRL_STATE_INIT "init"
#define PINCTRL_STATE_IDLE "idle"
#define PINCTRL_STATE_SLEEP "sleep"
device-treegpiolinux-device-driver