Linux SPI驱动学习——调用SPI读写函数

博客说明

撰写日期	2019.10.25
完稿日期	未完稿
最近维护	暂无
本文作者	multimicro
联系方式	[email protected]
资料链接	本文无附件资料
GitHub	https://github.com/wifialan/drivers/blob/master/w25q16_spi.c
原文链接	https://blog.csdn.net/multimicro/article/details/102738026

开发环境

环境说明	详细信息	备注信息
操作系统	Ubunut 18.04
开发板	JZ2440-V3
Linux内核	linux-3.4.2

1. 基于W25Q16型FLASH来看SPI的读写函数

这里将w25q16注册为了一个mtd设备，和字符设备最大不同点就是，不同的设备类型中的方法不同，对于flash硬件，注册为mtd设备会更加便于操作。这里给出源码供分析参考:

/*
 *  Driver for S3C2440 base board.
 *
 *  Copyright (C) 2019  Alan NWPU 
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *  MULTIBEANS, NPU Youyi West Ave, Beilin District, Xi'an, China.*/

#include    /* Every Linux kernel module must include this head */
#include      /* Every Linux kernel module must include this head */
#include    /* printk() */
#include        /* struct fops */
#include     /* error codes */
#include 
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#include 
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#include 


#define DRV_NAME "s3c2440_w25q16"
#define DRV_AUTHOR "Alan Tian "
#define DRV_DESC "S3C2440 W25Q16 Driver"


static int w25q16_bus_spi_probe(struct spi_device *spi);
static int w25q16_spi_remove(struct spi_device *spi);


struct spi_master *spi_master_p;
struct spi_device *spi_flash;
struct spi_message *spi_mesg_p;


void SPIFlashReadID(int *pMID, int *pDID)
{
    unsigned char tx_buf[4];
    unsigned char rx_buf[2];
    
    tx_buf[0] = 0x90;
    tx_buf[1] = 0;
    tx_buf[2] = 0;
    tx_buf[3] = 0;

    spi_write_then_read(spi_flash, tx_buf, 4, rx_buf, 2);		//先发送tx_buf数组里面的4个字节，然后在读取2个字节并存入rx_buf中

    *pMID = rx_buf[0];
    *pDID = rx_buf[1];
}

static void SPIFlashWriteEnable(int enable)
{
    unsigned char val = enable ? 0x06 : 0x04;
    spi_write(spi_flash, &val, 1);    
}

static unsigned char SPIFlashReadStatusReg1(void)
{
    unsigned char val;
    unsigned char cmd = 0x05;

    spi_write_then_read(spi_flash, &cmd, 1, &val, 1);
    
    return val;
}

static unsigned char SPIFlashReadStatusReg2(void)
{
    unsigned char val;
    unsigned char cmd = 0x35;

    spi_write_then_read(spi_flash, &cmd, 1, &val, 1);
    
    return val;
}

static void SPIFlashWaitWhenBusy(void)
{
    while (SPIFlashReadStatusReg1() & 1)
    {
        /* 休眠一段时间 */
        /* Sector erase time : 60ms
         * Page program time : 0.7ms
         * Write status reg time : 10ms
         */
		set_current_state(TASK_INTERRUPTIBLE);
        schedule_timeout(HZ/100);  /* 休眠10MS后再次判断 */
    }
}

static void SPIFlashWriteStatusReg(unsigned char reg1, unsigned char reg2)
{    
    unsigned char tx_buf[4];

    SPIFlashWriteEnable(1);  
    
    tx_buf[0] = 0x01;
    tx_buf[1] = reg1;
    tx_buf[2] = reg2;

    spi_write(spi_flash, tx_buf, 3);   

    SPIFlashWaitWhenBusy();
}

static void SPIFlashClearProtectForStatusReg(void)
{
    unsigned char reg1, reg2;

    reg1 = SPIFlashReadStatusReg1();
    reg2 = SPIFlashReadStatusReg2();

    reg1 &= ~(1<<7);
    reg2 &= ~(1<<0);

    SPIFlashWriteStatusReg(reg1, reg2);
}


static void SPIFlashClearProtectForData(void)
{
    /* cmp=0,bp2,1,0=0b000 */
    unsigned char reg1, reg2;

    reg1 = SPIFlashReadStatusReg1();
    reg2 = SPIFlashReadStatusReg2();

    reg1 &= ~(7<<2);
    reg2 &= ~(1<<6);

    SPIFlashWriteStatusReg(reg1, reg2);
}

/* erase 4K */
void SPIFlashEraseSector(unsigned int addr)
{
    unsigned char tx_buf[4];
    tx_buf[0] = 0x20;
    tx_buf[1] = addr >> 16;
    tx_buf[2] = addr >> 8;
    tx_buf[3] = addr & 0xff;

    SPIFlashWriteEnable(1);  

    spi_write(spi_flash, tx_buf, 4);

    SPIFlashWaitWhenBusy();
}

/* program */
void SPIFlashProgram(unsigned int addr, unsigned char *buf, int len)
{
    unsigned char tx_buf[4];   
	struct spi_transfer	t[] = {
            {
    			.tx_buf		= tx_buf,
    			.len		= 4,
        	},
			{
    			.tx_buf		= buf,
    			.len		= len,
			},
		};
	struct spi_message	m;

    tx_buf[0] = 0x02;
    tx_buf[1] = addr >> 16;
    tx_buf[2] = addr >> 8;
    tx_buf[3] = addr & 0xff;

    SPIFlashWriteEnable(1);  

	spi_message_init(&m);
	spi_message_add_tail(&t[0], &m);
	spi_message_add_tail(&t[1], &m);
	spi_sync(spi_flash, &m);

    SPIFlashWaitWhenBusy();    
}

void SPIFlashRead(unsigned int addr, unsigned char *buf, int len)
{
    /* spi_write_then_read规定了tx_cnt+rx_cnt < 32
     * 所以对于大量数据的读取，不能使用该函数
     */
     
    unsigned char tx_buf[4];   
	struct spi_transfer	t[] = {
            {
    			.tx_buf		= tx_buf,
    			.len		= 4,
        	},
			{
    			.rx_buf		= buf,
    			.len		= len,
			},
		};
	struct spi_message	m;

    tx_buf[0] = 0x03;
    tx_buf[1] = addr >> 16;
    tx_buf[2] = addr >> 8;
    tx_buf[3] = addr & 0xff;

	spi_message_init(&m);
	spi_message_add_tail(&t[0], &m);
	spi_message_add_tail(&t[1], &m);
	spi_sync(spi_flash, &m);    
}


static void SPIFlashInit(void)
{
    SPIFlashClearProtectForStatusReg();
    SPIFlashClearProtectForData();
}

/* 构造注册一个mtd_info
 * mtd_device_register(master, parts, nr_parts)
 *
 */

/* 首先: 构造注册spi_driver
 * 然后: 在spi_driver的probe函数里构造注册mtd_info
 */

static struct mtd_info spi_flash_dev;

static int spi_flash_erase(struct mtd_info *mtd, struct erase_info *instr)
{
    unsigned int addr = instr->addr;
    unsigned int len  = 0;

    /* 判断参数 */
    if ((addr & (spi_flash_dev.erasesize - 1)) || (instr->len & (spi_flash_dev.erasesize - 1)))
    {
        printk("addr/len is not aligned\n");
        return -EINVAL;
    }

    for (len = 0; len < instr->len; len += 4096)
    {
        SPIFlashEraseSector(addr);
        addr += 4096;
    }
    
	instr->state = MTD_ERASE_DONE;
	mtd_erase_callback(instr);
	return 0;
}

static int spi_flash_read(struct mtd_info *mtd, loff_t from, size_t len,
		size_t *retlen, u_char *buf)
{
    SPIFlashRead(from, buf, len);
	*retlen = len;
	return 0;
}

static int spi_flash_write(struct mtd_info *mtd, loff_t to, size_t len,
		size_t *retlen, const u_char *buf)
{
    unsigned int addr = to;
    unsigned int wlen  = 0;

    /* 判断参数 */
    if ((to & (spi_flash_dev.erasesize - 1)) || (len & (spi_flash_dev.erasesize - 1)))
    {
        printk("addr/len is not aligned\n");
        return -EINVAL;
    }

    for (wlen = 0; wlen < len; wlen += 256)
    {
        SPIFlashProgram(addr, (unsigned char *)buf, 256);
        addr += 256;
        buf += 256;
    }

	*retlen = len;
	return 0;
}



static struct spi_driver w25q16_spi_driver =
{
    .driver     =
    {
        .name   = "w25q16",
        .owner  = THIS_MODULE,
    },
    .probe      = w25q16_bus_spi_probe,
    .remove     = __devexit_p(w25q16_spi_remove),
};


static int __devinit w25q16_bus_spi_probe(struct spi_device *spi)
{ 
    int mid, did;
    printk("w25q16 probe function\n");
    spi_flash = spi;

    s3c2410_gpio_cfgpin(spi->chip_select, S3C2410_GPIO_OUTPUT);
    SPIFlashInit();
    SPIFlashReadID(&mid, &did);
    printk("SPI Flash ID: %02x %02x\n", mid, did);
    memset(&spi_flash_dev, 0, sizeof(spi_flash_dev));
    /* 构造注册一个mtd_info
     * mtd_device_register(master, parts, nr_parts)
     *
     */

	/* Setup the MTD structure */
	spi_flash_dev.name = "w25q16_flash";
	spi_flash_dev.type = MTD_NORFLASH;
	spi_flash_dev.flags = MTD_CAP_NORFLASH;
	spi_flash_dev.size = 0x200000;  /* 2M */
	spi_flash_dev.writesize = 1;
	spi_flash_dev.writebufsize = 4096; /* 没有用到 */
	spi_flash_dev.erasesize = 4096;  /* 擦除的最小单位 */

	spi_flash_dev.owner = THIS_MODULE;
	spi_flash_dev._erase = spi_flash_erase;
	spi_flash_dev._read  = spi_flash_read;
	spi_flash_dev._write = spi_flash_write;

    mtd_device_register(&spi_flash_dev, NULL, 0);
     
    return 0;

}

static int w25q16_spi_remove(struct spi_device *spi)
{
    mtd_device_unregister(&spi_flash_dev);
    return 0;

}


static int __init w25q16_driver_init(void)
{
    int ret;
    printk("\n************ driver init begin ************\n\n");
    ret = spi_register_driver(&w25q16_spi_driver);
    if(ret)
    {
        spi_unregister_driver(&w25q16_spi_driver);
        printk(DRV_NAME "\tFailed register spi driver. Error: %d\n",ret);
    }
    printk("\n************* driver init end *************\n\n");
    return ret;
}

static void __exit w25q16_driver_exit(void)
{
    printk("Unregister w25q16 flash!\n");
//    misc_deregister(&w25q16_miscdev);
    spi_unregister_driver(&w25q16_spi_driver);
}


module_init(w25q16_driver_init);
module_exit(w25q16_driver_exit);

MODULE_AUTHOR( DRV_AUTHOR );
MODULE_DESCRIPTION(DRV_DESC);
MODULE_LICENSE("GPL");

附录

1. Github： w25q16_spi.c