RK3568笔记四十九：W25Q64驱动开发（硬件SPI1)

若该文为原创文章，转载请注明原文出处。

一、SPI介绍

串行外设接口 (Serial Peripheral interface) 简称 SPI，是一种高速的，全双工，同步的通信总线，并 且在芯片的管脚上只占用四根线，节约了芯片的管脚。

而W25Q64是常见的串行闪存器件，W25Q64将8M字节的容量分为128个块，每个块大小为64K字节，每个块又分为16个扇区，每个扇区4K个字节。W25Q64的最小擦除单位为一个扇区，也就是每次必须擦除4K个字节。所以，这需要给W25Q64开辟一个至少4K的缓存区，这样必须要求芯片有4K以上的SRAM才能有很好的操作。

W25Q64的擦写周期多达10W次，可将数据保存达20年之久，支持2.7~3.6V的电压，支持标准的SPI，还支持双输出/四输出的SPI，最大SPI时钟可达80Mhz。

二、spi 基本知识

spi 总线都可以挂载多个设备，spi 支持标准的一主多从，全双工半双工通信等。

其中四根控制线 包括：

• SCK：时钟线，数据收发同步

• MOSI：数据线，主设备数据发送、从设备数据接收

• MISO：数据线，从设备数据发送，主设备数据接收

• NSS：片选信号线

i2c 通过 i2c 设备地址选择通信设备，而 spi 通过片选引脚选中要通信的设备。

spi 接口支持有多个片选引脚，连接多个 SPI 从设备，当然也可以使用外部 GPIO 扩展 SPI 设备的 数量，这样一个 spi 接口可连接的设备数由片选引脚树决定。

• 如果使用 spi 接口提供的片选引脚，spi 总线驱动会处理好什么时候选 spi 设备。

• 如果使用外部 GPIO 作为片选引脚需要我们在 spi 设备驱动中设置什么时候选中 spi。

(或者 在配置 SPI 时指定使用的片选引脚)。

通常情况下无特殊要求我们使用 spi 接口提供的片选引脚。

三、SPI时序

• 起始信号：NSS 信号线由高变低

• 停止信号：NSS 信号由低变高

• 数据传输：在 SCK 的每个时钟周期 MOSI 和 MISO 同时传输一位数据，高/低位传输没有硬 性规定

-- 传输单位：8 位或 16 位

-- 单位数量：允许无限长的数据传输

四、硬件原理分析

ATK-DLRK3568的外设IO有引出SPI1。

对应W25Q64接线如下：

|----------|-----------------------|
| W25Q64引脚 | ATK-DLRK3568 |
| 1-CS | GPIO3_A1 SPI1_CS0_M1 |
| 2-DO | GPIO3_C2 SPI1_MISO_M1 |
| 3-WP | 3.3V |
| 4-GND | GND |
| 5-DI | GPIO3_C1 SPI1_MOSI_M1 |
| 6-CLK | GPIO3_C3 SPI1_CLK_M1 |
| 7-HOLD | NC |
| 8-VCC | 3.3V |

使用杜邦线链接，确保接线正常。

五、创建设备节点

1、设备树节点

修改/home/alientek/rk3568_linux_sdk/kernel/arch/arm64/boot/dts/rockchip/目录下的rk3568-atk-evb1-ddr4-v10.dtsi文件，在文件末添加代码，在spi1设备树下添加w25q64节点。

&spi1 {
	status = "okay";
	pinctrl-names = "default", "high_speed";
	pinctrl-0 = <&spi1m1_cs0 &spi1m1_pins>;
	pinctrl-1 = <&spi1m1_cs0 &spi1m1_pins_hs>;
	
		  
	// 向 spi1 节点追加 w25q64 设备节点
	w25q64: w25q64@0 {
		compatible = "yifeng,w25q64";
		reg = <0>;  // 设置 reg 属性为 0, 表示 spi 连接到 spi1 的通道 0
		spi-max-frequency = <24000000>;  // 设置 SPI 传输的最大频率
		wp-gpio = <&gpio3 RK_PA1 GPIO_ACTIVE_HIGH>;
		pinctrl-0 = <&w25q64_wp>; /*<&w25q64_cs>; */
	};
};

2、创建设备的 pinctrl 节点

修改/home/alientek/rk3568_linux_sdk/kernel/arch/arm64/boot/dts/rockchip/目录下的rk3568-pinctrl.dtsi文件，在最后面增加节点

w25q64 {
		/omit-if-no-ref/
		w25q64_wp: w25q64-wp {
			rockchip,pins = <3 RK_PA1 RK_FUNC_GPIO &pcfg_pull_up>;
		};
	};

设备树修改完成以后在 SDK 顶层目录输入如下命令重新编译一下内核：

# 指定 SDK 的板级配置文件
./build.sh lunch
# 编译内核
./build.sh kernel

编译完成以后得到 boot.img, boot.img 就是编译出来的内核+设备树打包在一起的文件

只需要重新烧写boot.img。

烧写完成以后启动开发板。Linux 启动成功以后进入到/proc/device-tree/目录中查看是否有节点

六、编写驱动

1、spi_drv.c

#include <linux/module.h>//模块加载卸载函数
#include <linux/kernel.h>//内核头文件
#include <linux/types.h>//数据类型定义
#include <linux/fs.h>//file_operations结构体
#include <linux/device.h>//class_create等函数
#include <linux/ioctl.h>
#include <linux/kernel.h>/*包含printk等操作函数*/
#include <linux/of.h>/*设备树操作相关的函数*/
#include <linux/gpio.h>/*gpio接口函数*/
#include <linux/of_gpio.h>
#include <linux/platform_device.h>/*platform device*/
#include <linux/spi/spi.h> /*spi相关api*/
#include <linux/delay.h> /*内核延时函数*/
#include <linux/slab.h> /*kmalloc、kfree函数*/
#include <linux/cdev.h>/*cdev_init cdev_add等函数*/
#include <asm/uaccess.h>/*__copy_from_user 接口函数*/

#include <linux/moduleparam.h>
#include <linux/iio/iio.h>
#include <linux/iio/machine.h>
#include <linux/iio/driver.h>
#include <linux/iio/consumer.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/of_gpio.h>
#include <linux/semaphore.h>
#include <linux/timer.h>
#include <linux/irq.h>
#include <linux/wait.h>
#include <linux/poll.h>
#include <linux/fs.h>
#include <linux/fcntl.h>
#include <linux/platform_device.h>
#include <asm/uaccess.h>
#include <asm/io.h>


#define  DEVICE_NAME             "spi"
#define  W25Qxx_PAGE_SIZE        256        /*页 大小256字节*/
#define  W25QXX_SECTOR_SIZE      4096       /*扇区 大小4096*/

/*W25Qxx 指令*/
#define W25X_WriteEnable         0x06 
#define W25X_WriteDisable        0x04 
#define W25X_ReadStatusReg       0x05 
#define W25X_WriteStatusReg      0x01 
#define W25X_ReadData            0x03 
#define W25X_FastReadData        0x0B 
#define W25X_FastReadDual        0x3B 
#define W25X_PageProgram         0x02 
#define W25X_BlockErase          0xD8 
#define W25X_SectorErase         0x20 
#define W25X_ChipErase           0xC7 
#define W25X_PowerDown           0xB9 
#define W25X_ReleasePowerDown    0xAB 
#define W25X_DeviceID            0xAB 
#define W25X_ManufactDeviceID    0x90 
#define W25X_JedecDeviceID       0x9F 

typedef struct
{
   void *tx_buf;
   void *rx_buf;
   unsigned char cmd;            //w25q64指令
   unsigned int address;         //写入或者读取的地址
   unsigned int tx_len;          //需要写入的字节数
   unsigned int rx_len;          //需要读取的字节数

}w25qxx_data_def;

typedef struct
{
      struct device_node *node;//设备树节点
      struct cdev cdev;       //定义一个cdev结构体
      struct class *class;    //创建一个w25q64类
      struct device *device;  //创建一个w25q64设备 该设备是需要挂在w25q64类下面的
      int major;              //主设备号
      dev_t  dev_id;
      struct spi_device *spi; /*spi设备*/
      int cspin;              /*片选脚*/
      int wppin;
      struct mutex lock;
      w25qxx_data_def data;
}w25qxx_typdef;

static w25qxx_typdef w25qxx_dev;//定义一个w25q64设备

/*函数声明*/
static int w25qxx_read_bytes(w25qxx_typdef *w25q64,unsigned int address,unsigned char* buf,int count);

static int w25q64_spi_read_write(w25qxx_typdef *w25q64)
{
   struct spi_device *spi = w25q64->spi;
   struct spi_transfer xfer[2];
   struct spi_message msg;
   int ret = 0;
   unsigned char *buf,*readbuf;

   memset(&xfer, 0, sizeof(xfer));/*必须清0 否则无法spi_sync函数无法发送数据*/

   xfer[0].tx_buf = w25q64->data.tx_buf;
   xfer[0].len = w25q64->data.tx_len;
   
   buf = (unsigned char *)(w25q64->data.tx_buf);

   xfer[1].rx_buf = w25q64->data.rx_buf;
   xfer[1].len = w25q64->data.rx_len;

   spi_message_init(&msg);
   spi_message_add_tail(&xfer[0], &msg);

   if(w25q64->data.rx_len)
   {
      spi_message_add_tail(&xfer[1], &msg);
   }

   ret = spi_sync(spi, &msg); 
   if(ret != 0)
   {  
      printk("spi_sync failed %d\n", ret);
   }
   
   readbuf = (unsigned char *)(w25q64->data.rx_buf);
   return ret;
}

static void spi_wp_enable(void)
{
    gpio_set_value(w25qxx_dev.wppin, 1); 
}

static void spi_wp_disable(void)
{
   gpio_set_value(w25qxx_dev.wppin, 0); 
}

static void spi_cs_enable(void)
{
   //gpio_set_value(w25qxx_dev.cspin, 0); /* cs = 0 */
}

static void spi_cs_disable(void)
{
   //gpio_set_value(w25qxx_dev.cspin, 1); /* cs = 1 */
}

static void spi_write_enable(void)
{
   int ret;
   unsigned char tx_buf[1];

   spi_cs_enable();
    
   tx_buf[0] = W25X_WriteEnable;/*写使能指令*/
   w25qxx_dev.data.tx_buf= tx_buf; 
   w25qxx_dev.data.tx_len = 1;
   w25qxx_dev.data.rx_len = 0;

   ret = w25q64_spi_read_write(&w25qxx_dev);

   spi_cs_disable();
}

static void spi_write_disable(void)
{

   int ret;
   unsigned char tx_buf[1];
   spi_cs_enable();
    
   tx_buf[0] = W25X_WriteDisable;/*写失能指令*/
   
   w25qxx_dev.data.tx_buf= tx_buf; 
   w25qxx_dev.data.tx_len = 1;
   w25qxx_dev.data.rx_len = 0;

   ret = w25q64_spi_read_write(&w25qxx_dev);

   spi_cs_disable();
}

static int w25qxx_get_sr(w25qxx_typdef *w25q64)
{
   int ret = -EINVAL;
   unsigned char tx_buf[1];
   unsigned char rx_buf[1];
   
   spi_cs_enable();

   tx_buf[0] = W25X_ReadStatusReg;
   
   w25q64->data.tx_buf= tx_buf; 
   w25q64->data.tx_len = 1;

   w25q64->data.rx_buf = rx_buf;
   w25q64->data.rx_len = 1;
 
   ret = w25q64_spi_read_write(w25q64);

   spi_cs_disable();

   if(ret < 0)
   {
      printk("w25qxx_get_sr failed \n");
      return ret;
   }

   return rx_buf[0];
}

static int w25qxx_get_id(w25qxx_typdef *w25q64)
{
   int ret = -EINVAL;
   unsigned char tx_buf[4];
   unsigned char rx_buf[5];
   
   spi_cs_enable();

   tx_buf[0] = W25X_ManufactDeviceID;/*读取ID指令*/
   tx_buf[1] = 0x0;
   tx_buf[2] = 0x0;
   tx_buf[3] = 0x0;
   
   w25q64->data.tx_buf= tx_buf; 
   w25q64->data.tx_len = 4;

   w25q64->data.rx_buf = rx_buf;
   w25q64->data.rx_len = 2;
 
   ret = w25q64_spi_read_write(w25q64);

   spi_cs_disable();

   if(ret != 0)
   {
      printk("w25qxx_get_id failed %d\n",ret);
      return ret;
   }
   printk("rx_buf 0x%x 0x%x 0x%x 0x%x\n\r",rx_buf[0], rx_buf[1], rx_buf[2], rx_buf[3]);
   return (rx_buf[0] << 8 | rx_buf[1]);
}

static void w25qxx_Reset(w25qxx_typdef *w25q64)
{
   int ret = -EINVAL;
   unsigned char tx_buf[4];//
   unsigned char rx_buf[5];//

   spi_wp_disable(); 
   spi_cs_enable();

   udelay(2);
   tx_buf[0] = 0x66;/*读取ID指令*/
   tx_buf[1] = 0x99;

   
   w25q64->data.tx_buf= tx_buf; 
   w25q64->data.tx_len = 2;

   w25q64->data.rx_buf = rx_buf;
   w25q64->data.rx_len = 0;
 
   ret = w25q64_spi_read_write(w25q64);

   spi_cs_disable();
   spi_wp_enable();
   udelay(2);

   if(ret < 0)
   {
      printk("w25qxx_get_id failed %d\n",ret);
   }
   else
   {
       printk("w25qxx_ Init Success %d\n",ret); 
   }
}

static int w25qxx_wait_idle(void)
{
   int ret = -EINVAL; 
   do {
        ret = w25qxx_get_sr(&w25qxx_dev);
        if(ret < 0 )
        {
           return ret;/*通信错误*/
        }
        else
        {
            if(!(ret & 0x01))
            {
               return 0;/*w25q64空闲*/
            }
        }  
        /* REVISIT: at HZ=100, this is sloooow */
        msleep(10);
   } while(1);   
   return 1; 
}

static int w25qxx_erase_sector(w25qxx_typdef *w25q64,unsigned int address)
{
   int ret = -EINVAL;
   unsigned char tx_buf[4];//
   
   spi_write_enable();/*写保护关闭*/
   spi_cs_enable();

   tx_buf[0] = W25X_SectorErase;/*扇区擦除指令*/
   tx_buf[1] = (unsigned char)((address>>16) & 0xFF);
   tx_buf[2] = (unsigned char)((address>>8) & 0xFF);
   tx_buf[3] = (unsigned char)(address & 0xFF);
   
   w25q64->data.tx_buf= tx_buf; 
   w25q64->data.tx_len = 4;

   w25q64->data.rx_len = 0;
 
   ret = w25q64_spi_read_write(w25q64);

   spi_cs_disable();

   if(ret != 0)
   {
      printk("erase sector@%d failed %d\n",address,ret);
      return ret;
   }
   ret = w25qxx_wait_idle();/*等待flash内部操作完成*/
   spi_write_disable();/*写保护打开*/

   return ret;
}

static int w25qxx_erase_chip(w25qxx_typdef *w25q64)
{
   int ret = -EINVAL;
   unsigned char tx_buf[1];//
   
   spi_write_enable();/*写保护关闭*/
   spi_cs_enable();

   tx_buf[0] = W25X_ChipErase;/*扇区擦除指令*/

  
   w25q64->data.tx_buf= tx_buf; 
   w25q64->data.tx_len = 1;

   w25q64->data.rx_len = 0;
 
   ret = w25q64_spi_read_write(w25q64);

   spi_cs_disable();

   if(ret != 0)
   {
      printk("erase chip failed %d\n", ret);
      return ret;
   }
   ret = w25qxx_wait_idle();/*等待flash内部操作完成*/
   spi_write_disable();/*写保护打开*/

   return ret;
}

static int w25qxx_need_erase(unsigned char*old,unsigned char*new,int count)
{
   int i;
   unsigned char p;

   for ( i = 0; i < count; i++)
   {
      p = *old++;
      p = ~p; 
      
      if((p &(*new++))!=0)
      {
         return 1;
      }
   }
   return 0;
}

static int w25qxx_read_bytes(w25qxx_typdef *w25q64,unsigned int address,unsigned char* buf,int count)
{
   int ret = -EINVAL;
   unsigned char tx_buf[4];//
   
   spi_cs_enable();

   tx_buf[0] = W25X_ReadData;/*读取数据指令*/
   tx_buf[1] = (unsigned char)((address>>16) & 0xFF);
   tx_buf[2] = (unsigned char)((address>>8) & 0xFF);
   tx_buf[3] = (unsigned char)(address & 0xFF);
   
   w25q64->data.tx_buf= tx_buf; 
   w25q64->data.tx_len = 4;

   w25q64->data.rx_buf = buf;
   w25q64->data.rx_len = count;
 
   ret = w25q64_spi_read_write(w25q64);

   spi_cs_disable();

   if(ret != 0)
   {
      printk("read@%d ,%d bytes failed %d\n",address,count,ret);
      return ret;
   }

   return ret;
}

static int w25qxx_write_page(w25qxx_typdef *w25q64,unsigned int address,unsigned char* buf,int count)
{
   int ret = -EINVAL;
   unsigned char *tx_buf;/*数据缓冲区*/
   
   tx_buf = (unsigned char*)kzalloc(count+4,GFP_KERNEL);
   if(!tx_buf)
       return -ENOMEM;
 

   spi_write_enable();/*写保护关闭*/
   spi_cs_enable();

   tx_buf[0] = W25X_PageProgram;/*页写指令*/
   tx_buf[1] = (unsigned char)((address>>16) & 0xFF);
   tx_buf[2] = (unsigned char)((address>>8) & 0xFF);
   tx_buf[3] = (unsigned char)(address & 0xFF);
   
   memcpy(&tx_buf[4],buf,count);

   w25q64->data.tx_buf= tx_buf; 
   w25q64->data.tx_len = count+4;

   w25q64->data.rx_len = 0;/*不需要读*/
   
   //printk("tx_data:%d-%d-%d-%d,count=%d\n",tx_buf[4],tx_buf[5],tx_buf[6],tx_buf[7],w25q64->data.tx_len);

   ret = w25q64_spi_read_write(w25q64);

   spi_cs_disable();

   if(ret != 0)
   {
      printk("write page@%d ,%d bytes failed %d\n",address,count,ret);
      kfree(tx_buf);
      spi_write_disable();/*写保护打开*/
      return ret;
   }
   ret = w25qxx_wait_idle();
   kfree(tx_buf); 
   spi_write_disable();/*写保护打开*/
   return ret;
}

static int w25qxx_write_pages(w25qxx_typdef *w25q64,unsigned int address,unsigned char* buf,int count)
{
   int ret = -EINVAL;
   unsigned int remain_of_page,need_to_write;
   unsigned int sector_first_address,sector_offset;
   unsigned char *write_buf;/*数据缓冲区*/

   write_buf = (unsigned char*)kzalloc(4096,GFP_KERNEL);
   if(!write_buf)
       return -ENOMEM;

   /*获取指定地址所在扇区的扇区首地址*/    
   sector_first_address = address & (~(W25Qxx_PAGE_SIZE-1)) ;

   /*获取指定地址在所在扇区内的偏移量*/
   sector_offset = address % 4096;

   ret = w25qxx_read_bytes(w25q64,sector_first_address,write_buf,4096);//读出整个扇区
   if(ret < 0 )
   {
      return ret;
   }
   
   /*判断是否需要擦除*/
   if(w25qxx_need_erase(&write_buf[sector_offset],buf,count))
   {
      printk("erase\n");
      w25qxx_erase_sector(w25q64,sector_first_address);
   }
   
   kfree(write_buf);

   remain_of_page = W25Qxx_PAGE_SIZE - address%W25Qxx_PAGE_SIZE;//获取本页还剩多少个字节空间可写入
   need_to_write = remain_of_page;/*下一次最多可写remain_of_page个字节*/
   
   printk("sector_first_address=%d,sector_offset=%d\n",sector_first_address,sector_offset);

   printk("address=%d,count=%d\n",address,count);

   if(count <= need_to_write) 
   {
      /*需要写入的字节数少于剩余空间  直接写入实际字节数*/
      ret = w25qxx_write_page(w25q64,address,buf,count);
      return ret;
   }
   else
   {    
      do
      {
         printk("address=%d\n,need_to_write=%d\n",address,need_to_write); 
         ret = w25qxx_write_page(w25q64,address,buf,need_to_write);
         if(ret !=0)
         {
            return ret;
         }
         if(need_to_write == count)
         {
             break;
         }
         else
         {
            buf+=need_to_write;
            address+=need_to_write;
            count-=need_to_write;         
            if(count > W25Qxx_PAGE_SIZE)
            {
               need_to_write = W25Qxx_PAGE_SIZE;
            }
            else
            {
               need_to_write = count;
            }
         }        
      } while (1);  
   }
   return ret;
}

static int w25qxx_write_more_bytes(w25qxx_typdef *w25q64,unsigned int address,unsigned char* buf,int count)
{
   int ret = -EINVAL;
   unsigned int num_of_sector,remain_of_sector,sector_offset;
   unsigned int need_to_write;//sector_first_address
   unsigned char *write_buf;/*数据缓冲区*/
   
   write_buf = (unsigned char*)kzalloc(4096,GFP_KERNEL);
   if(!write_buf)
       return -ENOMEM;
   
   num_of_sector = address / W25QXX_SECTOR_SIZE;
   sector_offset = address % W25QXX_SECTOR_SIZE;
   remain_of_sector = W25QXX_SECTOR_SIZE - address % W25QXX_SECTOR_SIZE;/*当前地址所在扇区 还剩下多少空间*/
   
   need_to_write = remain_of_sector;

   if(count <= need_to_write)
   {
      ret = w25qxx_write_pages(w25q64,address,buf,count);
      return ret;
   }
   else
   {
       do
      {
         ret = w25qxx_write_pages(w25q64,address,buf,need_to_write);
         if(ret !=0)
         {
            return ret;
         }
         if(need_to_write == count)
         {
             break;
         }
         else
         {
            buf+=need_to_write;
            address+=need_to_write;
            count-=need_to_write;         
            if(count > W25QXX_SECTOR_SIZE)
            {
               need_to_write = W25QXX_SECTOR_SIZE;
            }
            else
            {
               need_to_write = count;
            }
         }        
      } while (1);  
   }
   return ret;
}

static int w25qxx_open(struct inode *inode, struct file *filp)
{
   filp->private_data = &w25qxx_dev;

   return 0;
}

static int w25qxx_release(struct inode* inode ,struct file *filp)
{
   // w25qxx_typdef *dev = (w25qxx_typdef *) filp->private_data;
   return 0;
}

static ssize_t w25qxx_write(struct file *filp, const char __user *buf, size_t count,loff_t *f_pos)
{  
  int ret;  
  unsigned char *write_buf;/*数据缓冲区*/
  w25qxx_typdef * dev = (w25qxx_typdef *) filp->private_data;
  unsigned char address = filp->f_pos;

  write_buf = (unsigned char*)kzalloc(count,GFP_KERNEL);
  if(!write_buf )
       return -ENOMEM;
  spi_wp_enable();

  if (copy_from_user(write_buf, buf, count))
  {
      kfree(write_buf);
      return -EFAULT;
  }

  printk("write = %d,count = %d\n", address, (int)count);
  
  ret = w25qxx_write_more_bytes(dev,address,write_buf,count);
  spi_wp_disable();
  kfree(write_buf);
  return ret;
}

static ssize_t w25qxx_read(struct file *filp,char __user *buf, size_t count,loff_t *f_pos)
{
  int ret;  
  unsigned char *read_buf;/*数据缓冲区*/
  w25qxx_typdef * dev = (w25qxx_typdef *) filp->private_data;
  unsigned char address = filp->f_pos;
  
  read_buf = (unsigned char*)kzalloc(count,GFP_KERNEL);
  if(!read_buf )
       return -ENOMEM;

  printk("read@%d,count:%d\n",address, (int)count);

  ret = w25qxx_read_bytes(dev,address,read_buf,count);
  
  if (copy_to_user(buf, read_buf, count))
  {
      ret = -EFAULT;
  }

  kfree(read_buf);
  return ret;
}

loff_t w25qxx_llseek(struct file *file, loff_t offset, int whence)
{
   loff_t ret,pos,oldpos;
   oldpos = file->f_pos;
   switch (whence) 
   {
      case SEEK_SET:
           pos = offset; 
         break;
      case SEEK_CUR:
           pos = oldpos + offset;
         break;
      case SEEK_END:
           pos = W25Qxx_PAGE_SIZE - offset;
         break;   
      default:
          printk("cmd not supported\n");
         break;
   }
   
   if(pos < 0 || pos > W25Qxx_PAGE_SIZE)
   {  
      printk("error: pos > W25Qxx_PAGE_SIZE !\n");
      ret = -EINVAL;
      return ret;
   }
   file->f_pos = pos;
   ret = offset;  
   return ret;
}

static struct file_operations w25qxx_fops={
   .owner      = THIS_MODULE,
   .open       = w25qxx_open,
   .write      = w25qxx_write,
   .read       = w25qxx_read,
   .release    = w25qxx_release,
   .llseek     = w25qxx_llseek,
};

static int w25qxx_probe(struct spi_device *spi)
{
   int ret = -1;
   const char *string = NULL;

    w25qxx_typdef *dev = &w25qxx_dev;
   
   printk("w25q64 probe!\n"); 
   /*获取设备节点*/
   w25qxx_dev.node = of_find_node_by_path("/spi@fe620000/w25q64@0");
   if(w25qxx_dev.node == NULL)
   {
     printk("device-tree:not found w25q64!\r\n"); 
     return -1;
   }
   
   /*读取w25q64设备节点的compatible属性值*/
   ret = of_property_read_string(w25qxx_dev.node,"compatible",&string);
   if(ret == 0)
   {
      printk("%s\n",string);
   }
   
   /*申请gpio 用作片选*/
   w25qxx_dev.wppin = of_get_named_gpio(w25qxx_dev.node,"wp-gpio",0);
   if(!gpio_is_valid(w25qxx_dev.wppin))
   {
     printk("get gpio error\n");
     ret = -EINVAL;
     return ret;
   }
   
   printk("gpio = %d\n",w25qxx_dev.wppin);

   ret = gpio_request(w25qxx_dev.wppin,"spi-wp");
   if(ret < 0) 
   {
      printk("gpio_request %d failed\n",w25qxx_dev.wppin);
      return ret;
   }
   gpio_direction_output(w25qxx_dev.wppin, 1);

   gpio_export(w25qxx_dev.wppin, 1);

   /*申请gpio 用作片选*/
   // w25qxx_dev.cspin = of_get_named_gpio(w25qxx_dev.node,"cs-gpios",0);
   // if(!gpio_is_valid(w25qxx_dev.cspin))
   // {
   //   printk("get gpio error\n");
   //   ret = -EINVAL;
   //   return ret;
   // }
   
   // printk("gpio = %d\n",w25qxx_dev.cspin);

   // ret = gpio_request(w25qxx_dev.cspin,"spi-cs");
   // if(ret < 0) 
   // {
   //    printk("gpio_request %d failed\n",w25qxx_dev.cspin);
   //    return ret;
   // }
   // gpio_direction_output(w25qxx_dev.cspin, 1);

   // gpio_export(w25qxx_dev.cspin, 1);
   
   /*申请设备号*/
   alloc_chrdev_region(&w25qxx_dev.dev_id,0,1,DEVICE_NAME);

   /*初始化一个cdev*/
   cdev_init(&w25qxx_dev.cdev,&w25qxx_fops);

   
   /*向cdev中添加一个设备*/
   cdev_add(&w25qxx_dev.cdev,w25qxx_dev.dev_id,1);

   /*创建一个norflash_class类*/
   w25qxx_dev.class = class_create(THIS_MODULE, "norflash_class");
   if(w25qxx_dev.class == NULL)
   {
      printk("class_create failed\r\n");
     return -1;
   }

   /*在eeprom_class类下创建一个eeprom_class设备*/
   w25qxx_dev.device = device_create(w25qxx_dev.class, NULL, w25qxx_dev.dev_id, NULL, DEVICE_NAME);

   /*获取与本驱动匹配的spi设备*/
   w25qxx_dev.spi = spi;

   //w25qxx_dev.spi->mode = SPI_MODE_3; /*spi flash对应的模式*/

   spi_setup(w25qxx_dev.spi);

   mutex_init(&dev->lock);

   w25qxx_Reset(&w25qxx_dev);

   mdelay(200);

   ret = w25qxx_erase_chip(&w25qxx_dev);
   if(ret < 0)
   {
       printk("w25qxx_erase_chip failed\r\n");
   }   

   ret = w25qxx_get_id(&w25qxx_dev);
   
   printk("id=%04x\n",ret);

   return  0;
}

static int w25qxx_remove(struct spi_device *spi)
{
   
    printk("w25qxx remove!\n"); 

    /*删除w25q64类*/
   cdev_del(&w25qxx_dev.cdev);

   /*释放w25q64设备号*/
   unregister_chrdev_region(w25qxx_dev.dev_id, 1);

   /*注销w25q64设备*/
   device_destroy(w25qxx_dev.class, w25qxx_dev.dev_id);

   /*注销w25q64类*/
   class_destroy(w25qxx_dev.class);

   gpio_free(w25qxx_dev.wppin);
   //gpio_free(w25qxx_dev.cspin);

   return 0;
}

static const struct of_device_id w25qxx_of_match[] = {
   {.compatible = "yifeng,w25q64"},
   {},
};

static const struct spi_device_id w25q64_id[] = {
   { "xxxx", 0 },
   {},
};

static struct spi_driver w25qxx_driver = {

   .driver = {
     .owner = THIS_MODULE,
      .name = "w25q64",
      .of_match_table = w25qxx_of_match,
   },
   .probe = w25qxx_probe,
   .remove  = w25qxx_remove,  
   .id_table   = w25q64_id,      
};

static int __init w25qxx_init(void)
{
   printk("module init ok\n");
   return spi_register_driver(&w25qxx_driver);
}

static void w25qxx_exit(void)
{
   spi_unregister_driver(&w25qxx_driver);
   printk("module exit ok\n");
}

module_init(w25qxx_init);
module_exit(w25qxx_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("w25q64 driver");
MODULE_AUTHOR("yifeng");

代码中获取设备节点需要注意：

w25qxx_dev.node = of_find_node_by_path("/spi@fe620000/w25q64@0");

这里的**/spi@fe620000/w25q64@0**需要先在开发板上确定。

片选引脚也需要指定。

2、makefile

KERNELDIR := /home/alientek/rk3568_linux_sdk/kernel
ARCH=arm64
CROSS_COMPILE=/opt/atk-dlrk356x-toolchain/usr/bin/aarch64-buildroot-linux-gnu-

export  ARCH  CROSS_COMPILE

CURRENT_PATH := $(shell pwd)
obj-m := spi_drv.o

build: kernel_modules

kernel_modules:
	$(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) modules
clean:
	$(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) clean

编译生成ko文件

七、应用程序编写

// APP应用 
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <limits.h>
#include <asm/ioctls.h>
#include <time.h>
#include <pthread.h>
#include<string.h>

#define  num 128

void print_data(const char *title, char *dat, int count)
{
   int i = 0; 

   printf(title);

   for(i = 0; i < count; i++) 
   {
      printf(" 0x%x", dat[i]);
   }
   printf("\n");
}

int main(int argc, char *argv[])
{
   int fd,ret,i;
   int count = num;
   int offset = 0;   
   char write_buf[num],read_buf[num];

   /*判断传入的参数是否合法*/
   if(argc != 2)
   {
      printf("Usage:error\n");
      return -1;
   }
  
   /*解析传入的参数*/
   offset =atoi(argv[1]);
   printf("offset = %d\n", offset);
 
    /*打开设备文件*/
   fd = open("/dev/spi", O_RDWR);
   if(fd < 0)
   {
      printf("open dev fail fd=%d\n",fd); 
      close(fd);
      return fd;
   }

   /*缓存数组赋值*/
   //memset(write_buf, 0x55, num);
   for(i = 0; i < num; i++)
   {
      write_buf[i] = i;
   }

    /*写入数据*/ 
   lseek(fd,offset,SEEK_SET);

   ret = write(fd,write_buf,num);

   if(ret < 0)
   {
      printf("write to w25qxx error\n");
      close(fd);
      return ret;
   }

   /*打印数据*/
   print_data("write to w25qxx: \n\r", write_buf, count);

   /*读取数据*/
   ret = lseek(fd,offset,SEEK_SET);
   printf("lseek = %d\n",ret);
   
   ret = read(fd, read_buf, count);
   if(ret < 0)
   {
      printf("read from w25qxx error\n");
      close(fd);
      return ret;
   }
   
   /*打印数据*/
   print_data("read from w25qxx: \n\r",read_buf, count);

   ret = memcmp(write_buf, read_buf, count);
   if(ret)
   {
      printf("Writing data is different from reading data...\n");
   }
   else
   {
      printf("Write data is the same as read data...\n");
   }
   close(fd);
   return 0;   
}

编译

/opt/atk-dlrk356x-toolchain/bin/aarch64-buildroot-linux-gnu-gcc spiApp.c -o spiApp

八、测试

测试比较简单，写入128个数，在读出来比较。

到此测试完成，使用硬件SPI正常。

但有个疑问使用ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);是怎么处理的，留个问题。

如有侵权，或需要完整代码，请及时联系博主。