NanoPi NEO小试牛刀（二）_allwinner drm

你好！这里是风筝的博客，

欢迎和我一起交流。

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前面写了NanoPi NEO的启动过程：NanoPi NEO小试牛刀（一）
但是我发现NanoPi NEO启动Linux内核时加载的东西太多了，Linux内核是没有经过剪裁的，我们可以试着剪裁优化下：

make menuconfig ARCH=arm CROSS_COMPILE=arm-linux-
1

Networking support —>Networking options—> Network packet filtering framework (Netfilter)    我不打算使用防火墙，要用到时再编译进去

Networking support—> < >CAN bus subsystem support     我不打算使用CAN总线

Networking support —> < > RF switch subsystem support     我没有RF 切换设备

Device Drivers —>< >Serial ATA and Parallel ATA drivers (libata)     SATA或PATA接口的硬盘或光驱等设备

Device Drivers —>[ ] Multiple devices driver support (RAID and LVM)     暂时没有要使用Raid （磁盘阵列）和LVM （逻辑卷管理器，添加，删除逻辑分区）的需求

Device Drivers —> <> Sound card support      暂时没有无声卡

Device Drivers —> Graphics support –>< > DRM Support for Allwinner A10 Display Engine      没有视频播放

[ ] Virtualization      不需要

把这些都取消掉，然后选择支持nfs，这个好用：
File systems —> Network File Systems     支持nfs

最后保存退出，编译出来的zImage文件就小好多了

现在可以试着写一个简单的驱动试一下效果：
led.c：

/*
 Port A(PA): 22 input/output port ? 
 Port C(PC): 19 input/output port ? 
 Port D(PD): 18 input/output port ? 
 Port E(PE) : 16 input/output port ? 
 Port F(PF) : 7 input/output port ? 
 Port G(PG) : 14 input/output port ? 
 Port L(PL) : 12 input/output port 

 PIO 0x01C20800 
 Pn_CFG0 n*0x24+0x00 Port n Configure Register 0 (n from 0 to 6)
 Pn_CFG1 n*0x24+0x04 Port n Configure Register 1 (n from 0 to 6)
 Pn_CFG2 n*0x24+0x08 Port n Configure Register 2 (n from 0 to 6)
 Pn_CFG3 n*0x24+0x0C Port n Configure Register 3 (n from 0 to 6)
 Pn_DAT n*0x24+0x10 Port n Data Register (n from 0 to 6)
 Pn_DRV0 n*0x24+0x14 Port n Multi-Driving Register 0 (n from 0 to 6)
 Pn_DRV1 n*0x24+0x18 Port n Multi-Driving Register 1 (n from 0 to 6)
 Pn_PUL0 n*0x24+0x1C Port n Pull Register 0 (n from 0 to 6)
 Pn_PUL1 n*0x24+0x20 Port n Pull Register 1 (n from 0 to 6)
*/

#include <linux/cdev.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/device.h>


//#include <linux/of_address.h>
//#include <linux/of_platform.h>


static volatile unsigned long *gpacon1;
static volatile unsigned long *gpadat;//a10



/*CFG0_REG Default Value: 0x7777777
 * [30:28] Pn7_SELECT
 * [26:24] Pn6_SELECT
 * [22:20] Pn5_SELECT
 * [18:16] Pn4_SELECT
 * [14:12] Pn3_SELECT
 * [10: 8] Pn2_SELECT
 * [ 6: 4] Pn1_SELECT
 * [ 2: 0] Pn0_SELECT
 *000:Input                001:Output  111:disable
 */

/*CFG1_REG Default Value: 0x7777777
 * [30:28] Pn15_SELECT
 * [26:24] Pn14_SELECT
 * [22:20] Pn13_SELECT
 * [18:16] Pn12_SELECT
 * [14:12] Pn11_SELECT
 * [10: 8] Pn10_SELECT
 * [ 6: 4] Pn9_SELECT
 * [ 2: 0] Pn8_SELECT
 *000:Input             001:Output 
 */

/*CFG2_REG Default Value: 0x7777777
 * [22:20] Pn21_SELECT
 * [18:16] Pn20_SELECT
 * [14:12] Pn19_SELECT
 * [10: 8] Pn18_SELECT
 * [ 6: 4] Pn17_SELECT
 * [ 2: 0] Pn16_SELECT
 *000:Input              001:Output  
*/

/*Pn_DAT Default Value: 0x0
 * [21:0] if input :read pin state; if outport : pin state is same bit
*/

static int led_open(struct inode *inode, struct file *file)   
{
    printk("this is nanopi neo led \n");
    *gpacon1 |= (0x01<<(8));//PA10=Output

    return 0;
}

static ssize_t led_read(struct file * file, char __user *buf, size_t count, loff_t *off)
{
    printk("read nanopi neo led \n");
    //*gpadat &= ~(0x01<<(10));//PA10=0
    *gpadat |= (0x01<<(10));//PA10=1


    return 0;
}

static ssize_t led_write(struct file *file, const char __user *buf,size_t count, loff_t *ppos)
{
    //*gpadat

    return 0;
}


static struct file_operations led10_fops = {
    .owner  = THIS_MODULE,
    .open   = led_open,
    .read   = led_read, 
    .write  = led_write,
};

/* 1. 确定主设备号 */
static int major;
static struct cdev led10_cdev;
static struct class *cls;

static int led_drv_init(void)
{
    int res;
    struct device * led_res;
    dev_t devid;

    /* 3. 告诉内核 */
#if 0
    major = register_chrdev(0, "hello", &hello_fops); /* (major,  0), (major, 1), ..., (major, 255)都对应hello_fops */
#else /*仅仅是注册设备号*/
    if (major) {
        devid = MKDEV(major, 0);
        register_chrdev_region(devid, 1, "led_blue");  /* (major,0) 对应 pwm_fops, (major, 1~255)都不对应pwm_fops */
    } else {
        alloc_chrdev_region(&devid, 0, 1, "led_blue"); /* (major,0) 对应 pwm_fops, (major, 1~255)都不对应pwm_fops */
        major = MAJOR(devid);                     
    }

    cdev_init(&led10_cdev, &led10_fops);
    res=cdev_add(&led10_cdev, devid, 1);
    if(res)
    {
        printk("cdev_add failed\n");
        unregister_chrdev_region(MKDEV(major, 0), 1);
        return 0;
    }
#endif

    cls = class_create(THIS_MODULE, "led_blue");
    led_res = device_create(cls, (struct device *)NULL, MKDEV(major, 0), (void *)NULL, (const char *)"led_blue"); /* /dev/xxx */
    if (IS_ERR((const void *)res)) 
    {
        printk("device_create failed\n");
        return 0;
    }

    gpacon1 = ioremap(0x01C20800+0*0x24+0x04 , 0x4*4);
    gpadat  = gpacon1+3;
    if (!gpacon1)
    {
        printk("ioremap failed\n");
        return -EIO;
    }

    return 0;
}

static void led_drv_exit(void)
{
    unregister_chrdev(major, "led_blue"); // 卸载
    device_destroy(cls,MKDEV(major, 0));
    class_destroy(cls);
    iounmap(gpacon1);
}

module_init(led_drv_init);
module_exit(led_drv_exit);

MODULE_LICENSE("GPL");

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这就是一个简单的控制PA10管脚的程序，测试了下，可以使用。