Linux 2.6下SPI设备模型--------基于AT91RM9200分析

以下转自http://blog.chinaunix.net/u3/96265/showart_1925533.html

 

Linux 2.6下SPI设备模型

--------基于AT91RM9200分析

       Atmel公司的ARM AT系列，其SPI驱动在kernel 2.6.23里已经包含。如果你打了at91-patch补丁的话，则在内核配置时要小心。在Device Drivers---- > Character devices ---- >取消选中SPI Driver(legacy) for at91rm9200 processor 。同时Device Drivers---- >SPI Support ---- > 选中SPI Support ,Atmel SPI Controler,同时选中 User mode SPI device driver support 。

SPI Driver(legacy) for at91rm9200 processor是保留选项，为了兼容以前版本。如果同时选中SPI Driver(legacy) for at91rm9200 processor，则在/sys里无法注册类spidev，也就无法将设备和驱动联系在一起。与现有atmel spi驱动发生冲突。

 

各选项对应的编译情况如下：

       [*]SPI support ---- Config_SPI  开启SPI功能

       [*]Debug support for SPI drivers ---- config SPI_DEBUG   开启SPI debug调试

       ----SPI Master Controller Drivers ---- depends on SPI_MASTER  生成spi.o

       <*>Atmel SPI Controller ---- config SPI_ATMEL 生成atmel_spi.o

       <*>Bitbanging SPI master ---- config SPI_BITBANG 生成spi_bitbang.o

       <*>AT91RM9200 Bitbang SPI Master  ---- CONFIG_SPI_AT91  spi_at91_bitbang.o

       ---- SPI Protocol Masters ---- depends on SPI_MASTER

      < >SPI EEPROMs from most vendors ---- config SPI_AT25 生成at25.o

       <*>User mode SPI device driver support ---- config SPI_SPIDEV 生成spidev.o

总线

注册SPI总线

#spi.c

       struct bus_type spi_bus_type = {

       .name             = "spi",   // spi总线名称

       .dev_attrs       = spi_dev_attrs,

       .match           = spi_match_device,

       .uevent           = spi_uevent,

       .suspend  = spi_suspend,

       .resume          = spi_resume,

};

spi总线将在sysfs/bus下显示。

其bus_type 结构表示总线，它的定义在中，如下

struct bus_type {

       const char             * name;

       struct module         * owner;

 

       struct kset             subsys;

       struct kset             drivers;

       struct kset             devices;

       struct klist             klist_devices;

       struct klist             klist_drivers;

 

       struct blocking_notifier_head bus_notifier;

 

       struct bus_attribute * bus_attrs;

       struct device_attribute    * dev_attrs;

       struct driver_attribute    * drv_attrs;

       struct bus_attribute drivers_autoprobe_attr;

       struct bus_attribute drivers_probe_attr;

 

       int           (*match)(struct device * dev, struct device_driver * drv);

       int           (*uevent)(struct device *dev, char **envp,

                              int num_envp, char *buffer, int buffer_size);

       int           (*probe)(struct device * dev);

       int           (*remove)(struct device * dev);

       void        (*shutdown)(struct device * dev);

 

       int (*suspend)(struct device * dev, pm_message_t state);

       int (*suspend_late)(struct device * dev, pm_message_t state);

       int (*resume_early)(struct device * dev);

       int (*resume)(struct device * dev);

 

       unsigned int drivers_autoprobe:1;

};

其中，当一个总线上的新设备或者新驱动被添加时，*match 函数会被调用。如果指定的驱动程序能够处理指定的设备，该函数返回非零值。

对于spi总线，我们必须调用bus_register(&spi_bus_type)进行注册。调用如果成功，SPI总线子系统将被添加到系统中，在sysfs的/sys/bus目录下可以看到。然后，我们就可以向这个总线添加设备了。代码见下：

static int __init spi_init(void)

{

       int    status;

 

       buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);

       if (!buf) {

              status = -ENOMEM;

              goto err0;

       }

 

       status = bus_register(&spi_bus_type);

       if (status < 0)

              goto err1;

 

       status = class_register(&spi_master_class);

       if (status < 0)

              goto err2;

       return 0;

 

err2:

       bus_unregister(&spi_bus_type);

err1:

       kfree(buf);

       buf = NULL;

err0:

       return status;

}

 

设备

spi设备的结构如下：

#spi.h

struct spi_device {

       struct device          dev;

       struct spi_master    *master;

       u32                max_speed_hz;

       u8                  chip_select;

       u8                  mode;

#define    SPI_CPHA     0x01                     /* clock phase */

#define    SPI_CPOL     0x02                     /* clock polarity */

#define    SPI_MODE_0 (0|0)                     /* (original MicroWire) */

#define    SPI_MODE_1 (0|SPI_CPHA)

#define    SPI_MODE_2 (SPI_CPOL|0)

#define    SPI_MODE_3 (SPI_CPOL|SPI_CPHA)

#define    SPI_CS_HIGH       0x04                     /* chipselect active high? */

#define    SPI_LSB_FIRST    0x08                     /* per-word bits-on-wire */

#define    SPI_3WIRE    0x10                     /* SI/SO signals shared */

#define    SPI_LOOP     0x20                     /* loopback mode */

       u8                  bits_per_word;

       int                  irq;

       void               *controller_state;

       void               *controller_data;

       const char             *modalias;

 

       /*

        * likely need more hooks for more protocol options affecting how

        * the controller talks to each chip, like:

        *  - memory packing (12 bit samples into low bits, others zeroed)

        *  - priority

        *  - drop chipselect after each word

        *  - chipselect delays

        *  - ...

        */

};

device结构中包含了设备模型核心用来模拟系统的信息。spidev还有设备的其他信息，因此spi设备结构包含在spidev_data结构里。

struct spidev_data {

       struct device          dev;

       struct spi_device    *spi;

       struct list_head       device_entry;

 

       struct mutex          buf_lock;

       unsigned         users;

       u8                  *buffer;

};

注册spi设备，

#spidev.c

static int spidev_probe(struct spi_device *spi)

{

       …

       …

status = device_register(&spidev->dev);

…

…

}

完成这个调用之后，我们就可以在sysfs中看到它了。

 

SPI设备驱动程序

spi驱动程序结构如下：

struct spi_driver {

       int                  (*probe)(struct spi_device *spi);

       int                  (*remove)(struct spi_device *spi);

       void               (*shutdown)(struct spi_device *spi);

       int                  (*suspend)(struct spi_device *spi, pm_message_t mesg);

       int                  (*resume)(struct spi_device *spi);

       struct device_driver      driver;

};

spi驱动程序注册函数如下：

int spi_register_driver(struct spi_driver *sdrv)

{

       sdrv->driver.bus = &spi_bus_type;

       if (sdrv->probe)

              sdrv->driver.probe = spi_drv_probe;

       if (sdrv->remove)

              sdrv->driver.remove = spi_drv_remove;

       if (sdrv->shutdown)

              sdrv->driver.shutdown = spi_drv_shutdown;

       return driver_register(&sdrv->driver);

}

spidev的驱动名如下：

static struct spi_driver spidev_spi = {

       .driver = {

              .name =          "spidev",

              .owner = THIS_MODULE,

       },

       .probe =  spidev_probe,

       .remove =       __devexit_p(spidev_remove),

};

一个spi_register_driver调用将spidev添加到系统中。一旦初始化完成，就可以在sysfs中看到驱动程序信息。

类

spidev类结构如下:

static struct class spidev_class = {

       .name             = "spidev",

       .owner           = THIS_MODULE,

       .dev_release    = spidev_classdev_release,

};

 

AT91RM9200 SPIDEV初始化

AT91RM9200的spi驱动，对于EK板，原先的SPI是用于dataflash的。其代码如下：

static struct spi_board_info ek_spi_devices[] = {

       {     /* DataFlash chip */

              .modalias = "mtd_dataflash",

              .chip_select    = 0,

              .max_speed_hz      = 15 * 1000 * 1000,

       }，

我们需要将.modalias改成我们自己的spi设备名

在spi设备初始化代码中，class_register(&spidev_class)注册类，spi_register_driver(&spidev_spi)注册spidev驱动。

#drivers/spi/spidev.c

static int __init spidev_init(void)

{

       int status;

 

       /* Claim our 256 reserved device numbers.  Then register a class

        * that will key udev/mdev to add/remove /dev nodes.  Last, register

        * the driver which manages those device numbers.

        */

       BUILD_BUG_ON(N_SPI_MINORS > 256);

       status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);

       if (status < 0)

              return status;

 

       status = class_register(&spidev_class);

       if (status < 0) {

              unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);

              return status;

       }

 

       status = spi_register_driver(&spidev_spi);

       if (status < 0) {

              class_unregister(&spidev_class);

              unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);

       }

       return status;

}

 

挂载/sys

mount –t sysfs sysfs /sys

可以看到有/sys/class/spidev/spidev0.0，表明设备已经挂载在总线上了，同时与驱动联系起来。

使用mdev –s，可以在/dev下看到spidev0.0这个设备了。

自此，spi设备驱动就可以工作了。

 

测试程序：

 

 

 

#include <stdio.h>

#include <unistd.h>

#include <stdlib.h>

#include <fcntl.h>

#include <string.h>

 

#include <sys/ioctl.h>

#include <sys/types.h>

#include <sys/stat.h>

 

#include <linux/types.h>

#include <linux/spi/spidev.h>

 

 

static int verbose;

 

static void do_read(int fd, int len)

{

       unsigned char buf[32], *bp;

       int status;

 

       /* read at least 2 bytes, no more than 32 */

       if (len < 2)

              len = 2;

       else if (len > sizeof(buf))

              len = sizeof(buf);

       memset(buf, 0, sizeof buf);

 

       status = read(fd, buf, len);

       if (status < 0) {

              perror("read");

              return;

       }

       if (status != len) {

              fprintf(stderr, "short read\n");

              return;

       }

 

       printf("read(%2d, %2d): %02x %02x,", len, status,

              buf[0], buf[1]);

       status -= 2;

       bp = buf + 2;

       while (status-- > 0)

              printf(" %02x", *bp++);

       printf("\n");

}

 

static void do_msg(int fd, int len)

{

       struct spi_ioc_transfer xfer[2];

       unsigned char buf[32], *bp;

       int status;

 

       memset(xfer, 0, sizeof xfer);

       memset(buf, 0, sizeof buf);

 

       if (len > sizeof buf)

              len = sizeof buf;

 

       buf[0] = 0xaa;

       xfer[0].tx_buf = (__u64) buf;

       xfer[0].len = 1;

 

       xfer[1].rx_buf = (__u64) buf;

       xfer[1].len = len;

 

       status = ioctl(fd, SPI_IOC_MESSAGE(2), xfer);

       if (status < 0) {

              perror("SPI_IOC_MESSAGE");

              return;

       }

 

       printf("response(%2d, %2d): ", len, status);

       for (bp = buf; len; len--)

              printf(" %02x", *bp++);

       printf("\n");

}

 

static void dumpstat(const char *name, int fd)

{

       __u8 mode, lsb, bits;

       __u32 speed;

 

       if (ioctl(fd, SPI_IOC_RD_MODE, &mode) < 0) {

              perror("SPI rd_mode");

              return;

       }

       if (ioctl(fd, SPI_IOC_RD_LSB_FIRST, &lsb) < 0) {

              perror("SPI rd_lsb_fist");

              return;

       }

       if (ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits) < 0) {

              perror("SPI bits_per_word");

              return;

       }

       if (ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed) < 0) {

              perror("SPI max_speed_hz");

              return;

       }

 

       printf("%s: spi mode %d, %d bits %sper word, %d Hz max\n",

              name, mode, bits, lsb ? "(lsb first) " : "", speed);

}

 

int main(int argc, char **argv)

{

       int c;

       int readcount = 0;

       int msglen = 0;

       int fd;

       const char *name;

 

       while ((c = getopt(argc, argv, "hm:r:v")) != EOF) {

              switch (c) {

              case 'm':

                     msglen = atoi(optarg);

                     if (msglen < 0)

                            goto usage;

                     continue;

              case 'r':

                     readcount = atoi(optarg);

                     if (readcount < 0)

                            goto usage;

                     continue;

              case 'v':

                     verbose++;

                     continue;

              case 'h':

              case '?':

usage:

                     fprintf(stderr,

                            "usage: %s [-h] [-m N] [-r N] /dev/spidevB.D\n",

                            argv[0]);

                     return 1;

              }

       }

 

       if ((optind + 1) != argc)

              goto usage;

       name = argv[optind];

 

       fd = open(name, O_RDWR);

       if (fd < 0) {

              perror("open");

              return 1;

       }

 

       dumpstat(name, fd);

 

       if (msglen)

              do_msg(fd, msglen);

 

       if (readcount)

              do_read(fd, readcount);

 

       close(fd);

       return 0;

}


 

 

备注：

如果要设置模式，速率等，则可仿照以下语句：

speed      =10*1000*1000; //10MHz

if (ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed) < 0) {

              perror("SPI max_speed_hz");

              return;

       }

默认spi_io_transfer时，每个字节之间有延时。在atmel_spi_setup.c文件里去掉该延时语句：

              /* TODO: DLYBS and DLYBCT */

       //csr |= SPI_BF(DLYBS, 10);

       //csr |= SPI_BF(DLYBCT, 10);

这样就可以达到无间隙快速传输批量数据。

标准read(),write()两个函数仅适用于半双工传输，。在传输之间不激活片选。而SPI_IOC_MESSAGE(N)则是全双工传输，并且片选始终激活。

SPI_IOC_MESSAGE传输长度有限制，默认是一页的长度，但是可以更改。

spi_ioc_transfer结构的spi长度 是字节长度，16位传输的时候要注意

 

 

 

 

以下转自http://blog.csdn.net/lanmanck/archive/2009/08/18/4459699.aspx

是原作者对上文的补充。

 

但是有的细节没有提到,我补充一下,不对请指出:

1、驱动中有总线和设备的概念。

spi控制器就是总线(spi总线)，对应atmel_spi.c

spi控制器上外接的芯片,比如串行flash、can收发器、时钟芯片等，就是设备。这就涉及到设备驱动的问题.

2、这些spi设备可以对应spidev.c,或者具体的文件.

比如说,我接的是flash芯片,那么可以定义spi_board_info 数组的时候指定:

static struct spi_board_info at_spi_board_info_all_devices[] =
{
    {    /* DataFlash chip mc13783*/
        .modalias    = "mtd_dataflash",   
        .chip_select    = 0,    //表示bus_num spi设备的片选号
        .max_speed_hz    = 20000000,
        .bus_num    = 0,        //表示用第几个spi
        .irq        = INT_NUM_MIX1,

    },

}

注意这个modalias,这里定义为mtd_dataflash,是因为有了mtd_dataflash.c这个文件,里面的probe函数用的名称就是"mtd_dataflash"

 

又比如说我接的的ads7846触摸屏芯片,可以这样定义:

{
        .modalias    = "ads7846",
        .chip_select    = 2,
        .max_speed_hz    = 125000 * 26,    /* (max sample rate @ 3V) * (cmd + data + overhead) */
        .bus_num    = 0,
        .platform_data    = &ads_info,
        .irq        = AT91SAM9261_ID_IRQ0,
},

这里的.modalias    = "ads7846",也因为有了ads7846.c这个文件,否则设备驱动无法probe成功,这样/dev下面就看不到设备了.

3、那如果我不想写具体的芯片驱动，就用自带的spi总线驱动怎么办呢？比如我接了一个can收发器。这就要用到spidev.c了.

打开spidev.c就可以发现标准的ioctl/read/write函数,这就是对应用户层的read write函数了,那么 spi_board_info的modalias需要这样定义:

.modalias    = "spidev",   

//不想写从设备驱动的话,就必须指定为"spidev",因为spidev.c就是这个设备的probe函数,里面有read/write/ioctl函数

这样设备启动后就可以在/dev看到spidev0.0字样. 0.0 就是bus_num.chip_select.

这下各位有点明白了吧.

 

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