设备树学习之（四）ADC 又见中断

最新推荐文章于 2025-06-10 13:48:58 发布

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最新推荐文章于 2025-06-10 13:48:58 发布

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分类专栏： Device Tree Tiny4412 DTS之Tiny4412 文章标签： devicetree adc interrupt

本文链接：https://blog.youkuaiyun.com/lizuobin2/article/details/54563985

Tiny4412 同时被 3 个专栏收录

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本文介绍如何在Tiny4412开发板上通过设备树配置实现ADC资源的使用，包括设备树的修改及相应驱动程序的编写，最终完成滑动变阻器电压的采集。

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开发板：tiny4412SDK + S702 + 4GB Flash
要移植的内核版本：Linux-4.4.0 （支持device tree）
u-boot版本：友善之臂自带的 U-Boot 2010.12
busybox版本：busybox 1.25

目标：
在第一篇文章中，学习了在设备树中增加GPIO资源，在代码中转为对应的中断，本文目标学习在设备树中直接使用中断资源，实现ADC采集底板上滑动变阻器的电压。

原理图：
这里写图片描述

设备树参考：

    adc: adc@126C0000 {
        compatible = "samsung,exynos-adc-v1";
        reg = <0x126C0000 0x100>;
        interrupt-parent = <&combiner>;
        interrupts = <10 3>;
        clocks = <&clock CLK_TSADC>;
        clock-names = "adc";
        #io-channel-cells = <1>;
        io-channel-ranges;
        samsung,syscon-phandle = <&pmu_system_controller>;
        status = "disabled";
    };

interrupt combiner 见芯片手册第10章，Interrupt combiner combines several interrupt sources as a group. Several interrupt requests in a group make a group interrupt request and a single request signal。一组中断源公用一个中断请求信号，2440也有类似例子。以ADC为例，它位于组INITG10的number3
这里写图片描述

samsung,exynos4210-combiner.txt
Required properties:
- compatible: should be "samsung,exynos4210-combiner".
- interrupt-controller: Identifies the node as an interrupt controller.
- #interrupt-cells: should be <2>. The meaning of the cells are
    * First Cell: Combiner Group Number.
    * Second Cell: Interrupt number within the group.
也就是：
        interrupt-parent = <&combiner>;
        interrupts = <10 3>;

设备树：

adc_demo@126C0000{
    compatible = "tiny4412,adc_demo";
    reg = <0x126C  0x20>;
    clocks = <&clock CLK_TSADC>;
    clock-names = "timers";
    interrupt-parent = <&combiner>;
    interrupts = <10 3>;
};

在代码中，我们仍可以向平台设备一样，使用

参考：Exynos_adc.c (drivers\iio\adc)   19412   2016/12/17
    irq = platform_get_irq(pdev, 0);
    if (irq < 0) {
        dev_err(&pdev->dev, "no irq resource?\n");
        return irq;
    }
    ...
    ret = request_irq(info->irq, exynos_adc_isr, 0, dev_name(&pdev->dev), info);

代码：

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/gpio.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/export.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/time.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/interrupt.h>

DECLARE_WAIT_QUEUE_HEAD(wait);

static int      major;
static struct   cdev    adc_cdev;
static struct   class   *cls;

struct ADC_BASE
{
    unsigned int ADCCON;    //0
    unsigned int temp0;     //
    unsigned int ADCDLY;    //8
    unsigned int ADCDAT;    //c
    unsigned int temp1;     //10
    unsigned int temp2;     //14
    unsigned int CLRINTADC; //18
    unsigned int ADCMUX;    //1c
};

volatile static struct ADC_BASE *adc_base = NULL;


static int adc_open(struct inode *inode, struct file *file)
{
    printk("adc_open\n");
    return 0;
}

static int adc_release(struct inode *inode, struct file *file)
{
    printk("adc_exit\n");
    return 0;
}

static ssize_t adc_read(struct file *filp, char __user *buf, size_t count, loff_t *off)
{
    int data = 0, ret = 0;
    printk("adc_read\n");
    adc_base->ADCMUX = 0x00;
    adc_base->ADCCON = (1 << 16 | 1 << 14 | 99 << 6 | 1 << 0);
    wait_event_interruptible(wait, ((adc_base->ADCCON >> 15) & 0x01));
    data = adc_base->ADCDAT & 0xfff;
    ret = copy_to_user(buf, &data, count);
    printk("copy_to_user %x\n", data);

    if (ret < 0)
    {
        printk("copy_to_user error\n");
        return -EFAULT;
    }

    return count;
}

static struct file_operations adc_fops =
{
    .owner              = THIS_MODULE,
    .open               = adc_open,
    .read               = adc_read,
    .release            = adc_release,
};

static irqreturn_t adc_demo_isr(int irq, void *dev_id)
{
    printk("enter irq now to wake up\n");
    wake_up(&wait);
    /* clear irq */
    adc_base->CLRINTADC = 1;
    return IRQ_HANDLED;
}

struct clk *base_clk;
int irq;
static int adc_probe(struct platform_device *pdev)
{
    dev_t devid;
    struct device *dev = &pdev->dev;
    struct resource *res = NULL;
    int ret;
    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

    if (res == NULL)
    {
        printk("platform_get_resource error\n");
        return -EINVAL;
    }

    base_clk = devm_clk_get(&pdev->dev, "timers");

    if (IS_ERR(base_clk))
    {
        dev_err(dev, "failed to get timer base clk\n");
        return PTR_ERR(base_clk);
    }

    ret = clk_prepare_enable(base_clk);

    if (ret < 0)
    {
        dev_err(dev, "failed to enable base clock\n");
        return -EINVAL;
    }

    printk("res: %x\n", (unsigned int)res->start);
    adc_base = devm_ioremap_resource(&pdev->dev, res);

    if (adc_base == NULL)
    {
        printk("devm_ioremap_resource error\n");
        goto err_clk;
    }

    printk("adc_base: %x\n", (unsigned int)adc_base);
    irq = platform_get_irq(pdev, 0);

    if (irq < 0)
    {
        dev_err(&pdev->dev, "no irq resource?\n");
        goto err_clk;
    }

    ret = request_irq(irq, adc_demo_isr, 0, "adc", NULL);

    if (ret < 0)
    {
        dev_err(dev, "failed to request_irq\n");
        goto err_clk;
    }

    if (alloc_chrdev_region(&devid, 0, 1, "adc") < 0)
    {
        printk("%s ERROR\n", __func__);
        goto err_req_irq;
    }

    major = MAJOR(devid);
    cdev_init(&adc_cdev, &adc_fops);
    cdev_add(&adc_cdev, devid, 1);
    cls = class_create(THIS_MODULE, "myadc");
    device_create(cls, NULL, MKDEV(major, 0), NULL, "adc");
    return 0;

err_req_irq:
    free_irq(irq, NULL);
err_clk:
    clk_disable(base_clk);
    clk_unprepare(base_clk);
    return -EINVAL;
}

static int adc_remove(struct platform_device *pdev)
{
    printk("enter %s\n", __func__);
    device_destroy(cls, MKDEV(major, 0));
    class_destroy(cls);
    cdev_del(&adc_cdev);
    unregister_chrdev_region(MKDEV(major, 0), 1);
    clk_disable(base_clk);
    clk_unprepare(base_clk);
    free_irq(irq, NULL);
    printk("%s enter.\n", __func__);
    return 0;
}

static const struct of_device_id adc_dt_ids[] =
{
    { .compatible = "tiny4412,adc_demo", },
    {},
};

MODULE_DEVICE_TABLE(of, adc_dt_ids);

static struct platform_driver adc_driver =
{
    .driver        = {
        .name      = "adc_demo",
        .of_match_table    = of_match_ptr(adc_dt_ids),
    },
    .probe         = adc_probe,
    .remove        = adc_remove,
};

static int adc_init(void)
{
    int ret;
    printk("enter %s\n", __func__);
    ret = platform_driver_register(&adc_driver);

    if (ret)
    {
        printk(KERN_ERR "adc demo: probe faiadc: %d\n", ret);
    }

    return ret;
}

static void adc_exit(void)
{
    printk("enter %s\n", __func__);
    platform_driver_unregister(&adc_driver);
}

module_init(adc_init);
module_exit(adc_exit);
MODULE_LICENSE("GPL");