SPI在linux3.14.78 FS_S5PC100(Cortex A8)和S3C2440上驱动移植(deep dive)
由于工作的原因,对SPI的理解最为深刻,也和SPI最有感情了,之前工作都是基于OSEK操作系统上进行实现,也在US/OS3上实现过SPI驱动的实现和测试,但是都是基于基本的寄存器操作,没有一个系统软件架构的思想,感觉linux SPI驱动很强大,水很深,废话少说,SPI总线上有两类设备:一类是主机端,通常作为SOC系统的一个子模块出现,比如很多嵌入式MPU中都常常包含SPI模块。一类是从机被控端,例如一些SPI接口的Flash、传感器等等。主机端是SPI总线的控制者,通过使用SPI协议主动发起SPI总线上的会话。而受控端则被动接受SPI主控端的指令,并作出响应的响应,本文读者前提是必须熟练掌握linux Platform总线驱动模型 和基本字符设备驱动的实现。
SPI总线由MISO(串行数据输入)、MOSI(串行数据输出)、SCK(串行移位时钟)、CS(使能信号)4个信号线组成。SPI常用四种数据传输模式,主要差别在于:输出串行同步时钟极性(CPOL)和相位(CPHA)可以进行配置。如果CPOL= 0,串行同步时钟的空闲状态为低电平;如果CPOL= 1,串行同步时钟的空闲状态为高电平。如果CPHA= 0,在串行同步时钟的前沿(上升或下降)数据被采样;如果CPHA = 1,在串行同步时钟的后沿(上升或下降)数据被采样。同I2C子系统类似,SPI子系统分为3个部分,分别是SPI核心层、主控制器驱动和协议驱动,通俗一点就是SPI核心层主要完成1.定义并注册SPI总线spi_bus_type和控制器类spi_master_class;2.提供spi_driver,spi_device和spi_master的分配,创建,注册和注销;3.实现SPI通信方法的上层代码。主控制器驱动对应I2C的适配器驱动,SPI用spi_master来描述相应的控制器,通常用spi_bitbang来控制实际的数据传输,功能非常类似与i2c_algorithm。协议驱动类比I2C设备驱动,可以理解成客户端驱动,下面详细分析和实现基于linux3.14.78内核版本 SPI在S3C2440/6410上驱动移植.
Step1,实现SPI控制器的设备接口(相对应有两种方式,一种实现方式是S3c2440纯粹通过配置来实现,另一种实现方式针对m25p10,独立编写单独的spi驱动模块)
首先针对S3C2440,SPI控制器的设备接口在drivers/spi/spidev.c中实现,下图为相应的软件流程图,spidev.c中的spidev_init()作为模块初始化函数,在系统启动或者模块加载是被调用,主要完成以下三种操作:
1、调用register_chrdev()为SPI控制器注册主设备号为153,次设备号范围为0~255,文件操作集合为spidev_fops的字符设备;
2、调用class_create()注册一个名为“spidev”的设备类;
3、调用spi_register_driver()向系统添加SPI控制器的设备驱动spidev_spi;
spi_register_driver()将驱动spidev_spi添加到SPI核心层注册的spi_bus_type总线上,注意,该总线属于spi总线,Spi总线对应的总线类型为spi_bus_type,在内核的drivers/spi/spi.c中定义,对应的匹配规则是(高版本中的匹配规则会稍有变化,引入了id_table,可以匹配多个spi设备名称)详见以下代码。由于spi总线的匹配方式是检查spi_device.modalias与spi_driver.driver.name是否相同,而spidev_spi的driver.name是“spidev”,so 只有spi_bus_type总线上的modalias为“spidev”的设备,才可以与spidev_spi驱动匹配。由于S3C2440拥有两个SPI控制器,对应的平台信息是s3c_device_spi0和s3c_device_spi1,可以将其添加到机器配置文件的My2440_devices数组中,驱动中probe方法中用到的总线编号、片选总数等信息来源于平台数据,这些数据需要用户添加,添加方式有两种,平台设备的平台数据类型是S3C2410_SPI_info,在板级初始化文件中可以为两个SPI平台设备分别定义和添加这些平台数据,此外为了支持SPI控制器设备接口功能,还需要在机器配置文件为SPI控制器设备添加并注册spi_board_info对象,详见下面代码。
设备与驱动匹配后,通过调用spidev_spi的probe方法来绑定工作见代码。SPI控制器设备操作集合是spidev_fops,主要包括spidev_write,spidev_read,spidev_ioctl,spidev_open和spidev_release。下面的代码注释中详尽分析了spidev_read()函数的实现过程,spidev_write()的分析和实现方法与read类似,spidev_open()会遍历device_list链表,找出其中设备号与打开设备文件的inode.i_rdev相等的spidev_data对象,并将该对象记录在文件的私有数据filp->private_data中,以供read和write函数获取,此外要实现全双工的传输需要借助控制器设备的ioctl方法,对应实现函数是spidev_ioctl(),全双工传输也是通过spidev_sync()完成的,与半双工传输唯一不同的是在消息的传输段中,tx_buffer和rx_buffer同时被设置,它还提供获取和修改时钟模式、子宽、最大时钟频率属性的命令。
1 static struct s3c2410_spi_info s3c2410_spi0_platdata = { 2 .pin_cs = S3C2410_GPG2, 3 .num_cs = 2, 4 .bus_num = 0, 5 .gpio_setup = s3c24xx_spi_gpiocfg_bus0_gpe11_12_13, 6 }; 7 static struct spi_board_info s3c2410_spi0_board[] = 8 { 9 [0] = { 10 .modalias = "spidev", 11 .bus_num = 0, 12 .chip_select = 0, 13 .max_speed_hz = 500 * 1000, 14 }, 15 [1] = { 16 .modalias = "at25", 17 .platform_data = &at25_eeprom_data, 18 .bus_num = 0, 19 .chip_select = 1, 20 .max_speed_hz = 500 * 1000, 21 } 22 }; 23 static struct s3c2410_spi_info s3c2410_spi1_platdata = { 24 .pin_cs = S3C2410_GPG3, 25 .num_cs = 1, 26 .bus_num = 1, 27 .gpio_setup = s3c24xx_spi_gpiocfg_bus1_gpg5_6_7, 28 }; 29 static struct spi_board_info s3c2410_spi1_board[] = 30 { 31 [0] = { 32 .modalias = "spidev", 33 .bus_num = 1, 34 .chip_select = 0, 35 .max_speed_hz = 500 * 1000, 36 } 37 }; 38 static void __init My2440_machine_init(void) 39 { 40 s3c24xx_fb_set_platdata(&My2440_fb_info); 41 s3c_i2c0_set_platdata(NULL); 42 i2c_register_board_info(0, i2c_devices, ARRAY_SIZE(i2c_devices)); 43 s3c_device_spi0.dev.platform_data= &s3c2410_spi0_platdata; 44 spi_register_board_info(s3c2410_spi0_board, ARRAY_SIZE(s3c2410_spi0_board)); 45 s3c_device_spi1.dev.platform_data= &s3c2410_spi1_platdata; 46 spi_register_board_info(s3c2410_spi1_board, ARRAY_SIZE(s3c2410_spi1_board)); 47 s3c_device_nand.dev.platform_data = &My2440_nand_info; 48 s3c_device_sdi.dev.platform_data = &My2440_mmc_cfg; 49 platform_add_devices(My2440_devices, ARRAY_SIZE(My2440_devices)); 50 }
1 struct bus_type spi_bus_type = { 2 .name = "spi", 3 .dev_attrs = spi_dev_attrs, 4 .match = spi_match_device, 5 .uevent = spi_uevent, 6 .suspend = spi_suspend, 7 .resume = spi_resume, 8 };
static int spi_match_device(struct device *dev, struct device_driver *drv){const struct spi_device *spi = to_spi_device(dev);return strcmp(spi->modalias, drv->name) == 0;}
static int spidev_probe(struct spi_device *spi) {struct spidev_data *spidev;int status;unsigned long minor;/* Allocate driver data, 分配并初始化一个spidev_data对象,用来描述SPI控制器设备驱动操作的控制器设备,包含它的设备号,传输缓存和内嵌spi_device*/spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);if (!spidev)return -ENOMEM;/* Initialize the driver data ,将与spidev_spi驱动匹配的spi_device赋值给spidev_data.spi,通过find_first_zero_bit()从位图minors中分配到次设备号,与主设备号SPIDEV_MAJOR构成设备号并赋值给spidev_data.devt,然后调用device_create()在/dev下创建名称格式为“spidev%d%d”的字符设备文件,第一个%d表示控制器编号,即spi_device.master.bus_num,第二个对应片选号,即spi_device.chip_select*/spidev->spi = spi;spin_lock_init(&spidev->spi_lock);mutex_init(&spidev->buf_lock);INIT_LIST_HEAD(&spidev->device_entry);/* If we can allocate a minor number, hook up this device.* Reusing minors is fine so long as udev or mdev is working.*/mutex_lock(&device_list_lock);minor = find_first_zero_bit(minors, N_SPI_MINORS);if (minor < N_SPI_MINORS) {struct device *dev;spidev->devt = MKDEV(SPIDEV_MAJOR, minor);dev = device_create(spidev_class, &spi->dev, spidev->devt,spidev, "spidev%d.%d",spi->master->bus_num, spi->chip_select);status = PTR_ERR_OR_ZERO(dev);} else {dev_dbg(&spi->dev, "no minor number available!\n");status = -ENODEV;}if (status == 0) {set_bit(minor, minors); /*将spidev_data对象添加到一个名为device_list的设备列表中,最后将spidev_data对象设置为对应spi_device的驱动数据,将其值赋值给dpi_device.dev.driver_data*/list_add(&spidev->device_entry, &device_list);}mutex_unlock(&device_list_lock);if (status == 0)spi_set_drvdata(spi, spidev);elsekfree(spidev);return status; }
/*spidev_read(),spidev_write()实现的读写操作都是半双工的传输,要实现全双工传输需要调用spidev_ioctl()操作,在spidev_read()中,通过调用spidev_sync_read()同步读取指定长度数据到spidev_data_buffer中,然后调用copy_to_user()将读取的数据复制到用户空间缓冲*/
static ssize_t spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) {struct spidev_data *spidev;ssize_t status = 0;/* chipselect only toggles at start or end of operation */if (count > bufsiz)return -EMSGSIZE;spidev = filp->private_data;mutex_lock(&spidev->buf_lock);status = spidev_sync_read(spidev, count);if (status > 0) {unsigned long missing;missing = copy_to_user(buf, spidev->buffer, status);if (missing == status)status = -EFAULT;elsestatus = status - missing;}mutex_unlock(&spidev->buf_lock);return status; }
/*spidev_sync_read()中定义一个spi_transfer和spi_message对象,使用spidev_data.buffer初始化spi_transfer.rx_buf,然后将spi_transfer对象添加到spi_message中,调用spidev_sync()传输信息;*/spidev_sync_read(struct spidev_data *spidev, size_t len)
{struct spi_transfer t = {.rx_buf = spidev->buffer,.len = len,};struct spi_message m;spi_message_init(&m);spi_message_add_tail(&t, &m);return spidev_sync(spidev, &m); }
/*spidev_sync()实现同步传输的机制:首先为传入的消息对象的complete和context成员赋值,context被设置为完成接口done,complete被设置成spidev_complete(),然后 调用spi_async()启动异步传输,spi_async()返回后,通过调用wait_for_completion()阻塞调用进程,直到异步传输完成,spi_message的complete方法,即spidev_complete() 被调用来唤醒被阻塞的进程,异步传输接口函数spi_async()属于SPI核心层,在include/linux/spi/spi.h中定义并实现,它只调用了spi_device所属控制器的transfer方法*/ static ssize_t spidev_sync(struct spidev_data *spidev, struct spi_message *message) {DECLARE_COMPLETION_ONSTACK(done);int status;message->complete = spidev_complete;message->context = &done;spin_lock_irq(&spidev->spi_lock);if (spidev->spi == NULL)status = -ESHUTDOWN;elsestatus = spi_async(spidev->spi, message);spin_unlock_irq(&spidev->spi_lock);if (status == 0) {wait_for_completion(&done);status = message->status;if (status == 0)status = message->actual_length;}return status; }
针对FS_S5PC100上的M25P10芯片,
//spi_device对应的含义是挂接在spi总线上的一个设备,所以描述它的时候应该明确它自身的设备特性、传输要求、及挂接在哪个总线上 static struct spi_board_info s3c_spi_devs[] __initdata = {{.modalias = "m25p10", .mode = SPI_MODE_0, //CPOL=0, CPHA=0 此处选择具体数据传输模式.max_speed_hz = 10000000, //最大的spi时钟频率/* Connected to SPI-0 as 1st Slave */.bus_num = 0, //设备连接在spi控制器0上.chip_select = 0, //片选线号,在S5PC100的控制器驱动中没有使用它作为片选的依据,而是选择了下文controller_data里的方法.controller_data = &smdk_spi0_csi[0],},};static struct s3c64xx_spi_csinfo smdk_spi0_csi[] = {[0] = {.set_level = smdk_m25p10_cs_set_level,.fb_delay = 0x3,},};static void smdk_m25p10_cs_set_level(int high) //spi控制器会用这个方法设置cs{u32 val;val = readl(S5PC1XX_GPBDAT);if (high)val |= (1<<3);elseval &= ~(1<<3);writel(val, S5PC1XX_GPBDAT);} spi_register_board_info(s3c_spi_devs, ARRAY_SIZE(s3c_spi_devs));//注册spi_board_info,这个代码会把spi_board_info注册要链表board_list上。 //spi_master的注册会在spi_register_board_info之后,spi_master注册的过程中会调用scan_boardinfo扫描board_list,找到挂接在它上面的spi设备,然后创建并注册spi_device。 static void scan_boardinfo(struct spi_master *master){struct boardinfo *bi;mutex_lock(&board_lock);list_for_each_entry(bi, &board_list, list) {struct spi_board_info *chip = bi->board_info;unsigned n;for (n = bi->n_board_info; n > 0; n--, chip++) {if (chip->bus_num != master->bus_num)continue;/* NOTE: this relies on spi_new_device to* issue diagnostics when given bogus inputs*/(void) spi_new_device(master, chip); //创建并注册了spi_device}}mutex_unlock(&board_lock);} //spi_driver.c linux内核中的/driver/mtd/devices/m25p80.c驱动为参考 static struct spi_driver m25p80_driver = { //spi_driver的构建.driver = {.name = "m25p80",.bus = &spi_bus_type,.owner = THIS_MODULE,},.probe = m25p_probe,.remove = __devexit_p(m25p_remove),*/}; spi_register_driver(&m25p80_driver);//spi driver的注册 //在有匹配的spi device时,会调用m25p_probe,根据传入的spi_device参数,可以找到对应的spi_master。接下来就可以利用spi子系统为我们完成数据交互了 static int __devinit m25p_probe(struct spi_device *spi)
Step2,实现SPI platform 总线匹配
S3C2440和S5PC100的SPI控制器驱动的实现同样采用了Platform驱动模型,针对S3C2440在drivers/spi/spi_s3c24xx.c中,模块初始化函数s3c24xx_spi_init()完成了platform驱动的注册,名称是“s3c2410-spi”,与该驱动匹配的平台设备在arch/arm/plat-samsung/devs.c中定义,并且与驱动同名,针对S5PC100,详见下面代码,匹配完成后调用相应的probe:
//Platform_device,SPI控制器对应platform_device的定义方式,同样以S5PC100中的SPI控制器为例,参看arch/arm/plat-s5pc1xx/dev-spi.c文件 struct platform_device s3c_device_spi0 = {.name = "s3c64xx-spi", //名称,要和Platform_driver匹配.id = 0, //第0个控制器,S5PC100中有3个控制器.num_resources = ARRAY_SIZE(s5pc1xx_spi0_resource), //占用资源的种类.resource = s5pc1xx_spi0_resource, //指向资源结构数组的指针.dev = {.dma_mask = &spi_dmamask, //dma寻址范围 .coherent_dma_mask = DMA_BIT_MASK(32), //可以通过关闭cache等措施保证一致性的dma寻址范围.platform_data = &s5pc1xx_spi0_pdata, //特殊的平台数据,参看后文},}; static struct s3c64xx_spi_cntrlr_info s5pc1xx_spi0_pdata = {.cfg_gpio = s5pc1xx_spi_cfg_gpio, //用于控制器管脚的IO配置.fifo_lvl_mask = 0x7f,.rx_lvl_offset = 13,}; static int s5pc1xx_spi_cfg_gpio(struct platform_device *pdev){switch (pdev->id) {case 0:s3c_gpio_cfgpin(S5PC1XX_GPB(0), S5PC1XX_GPB0_SPI_MISO0);s3c_gpio_cfgpin(S5PC1XX_GPB(1), S5PC1XX_GPB1_SPI_CLK0);s3c_gpio_cfgpin(S5PC1XX_GPB(2), S5PC1XX_GPB2_SPI_MOSI0);s3c_gpio_setpull(S5PC1XX_GPB(0), S3C_GPIO_PULL_UP);s3c_gpio_setpull(S5PC1XX_GPB(1), S3C_GPIO_PULL_UP);s3c_gpio_setpull(S5PC1XX_GPB(2), S3C_GPIO_PULL_UP);break; case 1:s3c_gpio_cfgpin(S5PC1XX_GPB(4), S5PC1XX_GPB4_SPI_MISO1);s3c_gpio_cfgpin(S5PC1XX_GPB(5), S5PC1XX_GPB5_SPI_CLK1);s3c_gpio_cfgpin(S5PC1XX_GPB(6), S5PC1XX_GPB6_SPI_MOSI1);s3c_gpio_setpull(S5PC1XX_GPB(4), S3C_GPIO_PULL_UP);s3c_gpio_setpull(S5PC1XX_GPB(5), S3C_GPIO_PULL_UP);s3c_gpio_setpull(S5PC1XX_GPB(6), S3C_GPIO_PULL_UP);break; case 2:s3c_gpio_cfgpin(S5PC1XX_GPG3(0), S5PC1XX_GPG3_0_SPI_CLK2);s3c_gpio_cfgpin(S5PC1XX_GPG3(2), S5PC1XX_GPG3_2_SPI_MISO2);s3c_gpio_cfgpin(S5PC1XX_GPG3(3), S5PC1XX_GPG3_3_SPI_MOSI2);s3c_gpio_setpull(S5PC1XX_GPG3(0), S3C_GPIO_PULL_UP);s3c_gpio_setpull(S5PC1XX_GPG3(2), S3C_GPIO_PULL_UP);s3c_gpio_setpull(S5PC1XX_GPG3(3), S3C_GPIO_PULL_UP);break; default:dev_err(&pdev->dev, "Invalid SPI Controller number!");return -EINVAL;} //platform_driver,参看drivers/spi/spi_s3c64xx.c文件 static struct platform_driver s3c64xx_spi_driver = {.driver = {.name = "s3c64xx-spi", //名称,和platform_device对应.owner = THIS_MODULE,},.remove = s3c64xx_spi_remove,.suspend = s3c64xx_spi_suspend,.resume = s3c64xx_spi_resume,}; platform_driver_probe(&s3c64xx_spi_driver, s3c64xx_spi_probe);//注册s3c64xx_spi_driver //和平台中注册的platform_device匹配后,调用s3c64xx_spi_probe。然后根据传入的platform_device参数,构建一个用于描述SPI控制器的结构体spi_master,并注册。spi_register_master(master)。后续注册的spi_device需要选定自己的spi_master,并利用spi_master提供的传输功能传输spi数据。和I2C类似,SPI也有一个描述控制器的对象叫spi_master,其主要成员是主机控制器的序号(系统中可能存在多个SPI主机控制器)、片选数量、SPI模式和时钟设置用到的函数、数据传输用到的函数等; struct spi_master {struct device dev;s16 bus_num; //表示是SPI主机控制器的编号。由平台代码决定u16 num_chipselect; //控制器支持的片选数量,即能支持多少个spi设备int (*setup)(struct spi_device *spi); //针对设备设置SPI的工作时钟及数据传输模式等。在spi_add_device函数中调用。int (*transfer)(struct spi_device *spi,struct spi_message *mesg); //实现数据的双向传输,可能会睡眠void (*cleanup)(struct spi_device *spi); //注销时调用};
static int s3c24xx_spi_probe(struct platform_device *pdev) {struct s3c2410_spi_info *pdata;struct s3c24xx_spi *hw;struct spi_master *master;struct resource *res;int err = 0;master = spi_alloc_master(&pdev->dev, sizeof(struct s3c24xx_spi));//分配SPI控制器结构及驱动私有数据if (master == NULL) {dev_err(&pdev->dev, "No memory for spi_master\n");return -ENOMEM;}hw = spi_master_get_devdata(master);memset(hw, 0, sizeof(struct s3c24xx_spi));hw->master = master;hw->pdata = pdata = dev_get_platdata(&pdev->dev);hw->dev = &pdev->dev;if (pdata == NULL) {dev_err(&pdev->dev, "No platform data supplied\n");err = -ENOENT;goto err_no_pdata;}platform_set_drvdata(pdev, hw);//将SPI控制器私有数据作为平台设备驱动数据,便于通过相应接口获得init_completion(&hw->done);//初始化完成接口/* initialise fiq handler */s3c24xx_spi_initfiq(hw);/* setup the master state. *//* the spi->mode bits understood by this driver: */master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;master->num_chipselect = hw->pdata->num_cs;//设置控制器片选总数和总线编号master->bus_num = pdata->bus_num;/* setup the state for the bitbang driver 初始化bitbang驱动的相关成员*/hw->bitbang.master = hw->master;hw->bitbang.setup_transfer = s3c24xx_spi_setupxfer;hw->bitbang.chipselect = s3c24xx_spi_chipsel;hw->bitbang.txrx_bufs = s3c24xx_spi_txrx;hw->master->setup = s3c24xx_spi_setup;hw->master->cleanup = s3c24xx_spi_cleanup;dev_dbg(hw->dev, "bitbang at %p\n", &hw->bitbang);/* find and map our resources 这是平台驱动中最常规的工作,找到并映射资源*/res = platform_get_resource(pdev, IORESOURCE_MEM, 0);hw->regs = devm_ioremap_resource(&pdev->dev, res);if (IS_ERR(hw->regs)) {err = PTR_ERR(hw->regs);goto err_no_pdata;}hw->irq = platform_get_irq(pdev, 0);if (hw->irq < 0) {dev_err(&pdev->dev, "No IRQ specified\n");err = -ENOENT;goto err_no_pdata;}err = devm_request_irq(&pdev->dev, hw->irq, s3c24xx_spi_irq, 0,pdev->name, hw);if (err) {dev_err(&pdev->dev, "Cannot claim IRQ\n");goto err_no_pdata;}hw->clk = devm_clk_get(&pdev->dev, "spi");//获取SPI的时钟资源if (IS_ERR(hw->clk)) {dev_err(&pdev->dev, "No clock for device\n");err = PTR_ERR(hw->clk);goto err_no_pdata;}/* setup any gpio we can 设置片选方法并配置片选引脚 */if (!pdata->set_cs) {if (pdata->pin_cs < 0) {dev_err(&pdev->dev, "No chipselect pin\n");err = -EINVAL;goto err_register;}err = devm_gpio_request(&pdev->dev, pdata->pin_cs,dev_name(&pdev->dev));if (err) {dev_err(&pdev->dev, "Failed to get gpio for cs\n");goto err_register;}hw->set_cs = s3c24xx_spi_gpiocs;gpio_direction_output(pdata->pin_cs, 1);} elsehw->set_cs = pdata->set_cs;s3c24xx_spi_initialsetup(hw);//使能SPI时钟,初始化2440 SPI控制器寄存器及片选引脚等/* register our spi controller 注册SPI控制器,进而完成对控制器对象的分配初始化和注册,注册控制器会扫描board_list链表,从中取出spi_board_info创建spi_device设备,因此在执行probe方法时,只要board_list链表上有控制器对应的spi_board_info,就能创建出控制器的设备对象,并与控制器设备驱动匹配,进而创建出用于访问该控制器的设备文件*/err = spi_bitbang_start(&hw->bitbang);if (err) {dev_err(&pdev->dev, "Failed to register SPI master\n");goto err_register;}return 0;err_register:clk_disable(hw->clk);err_no_pdata:spi_master_put(hw->master);return err; }
Step3,分析实现SPI总线通信方法
SPI控制器通常由spi_bitbang来完成实际数据的数据传输,spi_bitbang的定义如下:
struct spi_bitbang {spinlock_t lock; /*操作工作队列时使用的自旋锁*/u8 busy;u8 use_dma;u8 flags; /* extra spi->mode support */struct spi_master *master;/* setup_transfer() changes clock and/or wordsize to match settings* for this transfer; zeroes restore defaults from spi_device.为特定的传输设置时钟、字宽等属性的方法*/int (*setup_transfer)(struct spi_device *spi,struct spi_transfer *t);void (*chipselect)(struct spi_device *spi, int is_on); #define BITBANG_CS_ACTIVE 1 /* normally nCS, active low */ #define BITBANG_CS_INACTIVE 0/* txrx_bufs()为实际的传输方法 may handle dma mapping for transfers that don't* already have one (transfer.{tx,rx}_dma is zero), or use PIO*/int (*txrx_bufs)(struct spi_device *spi, struct spi_transfer *t);/* txrx_word[SPI_MODE_*]()按字传输的方法 just looks like a shift register */u32 (*txrx_word[4])(struct spi_device *spi,unsigned nsecs,u32 word, u8 bits); };
两者的SPI总线通信控制方法不同,在上面spi_bitbang结构可以看出,消息传输启动利用的是spi_bibang_txrx_bufs(),在2440 SPI驱动中是通过s3c24xx_spi_txrx()来实现,他将传输段中请求数据的缓冲区和长度赋值给s3c24xx_spi对象的相关成员,然后主动发送一个字节数据,启动传输过程,之后使用进程阻塞在完成接口s3c24xx_spi.done上,其他数据的传输将在中断处理函数中完成,中断检查到发送完成后,通知完成接口,唤醒之前阻塞在其上的进程(这里特别说明下6410SPI通信方法,与2440不同,采用DMA传输,相应的实现函数为s3c64xx_spi_transfer(),利用工作队列进行延迟调度),m25p80SPI总线通信控制详尽代码如下,说明一点,spi_message的消息可以同步传输也可以异步传输,正常产品中基本上都是异步传输,传输结束时有spi_message.complete()方法完成,下面的例子以同步实现简单实现:
#include <linux/platform_device.h> #include <linux/spi/spi.h> #include <linux/init.h>#include <linux/module.h>#include <linux/device.h>#include <linux/interrupt.h>#include <linux/mutex.h>#include <linux/slab.h> // kzalloc#include <linux/delay.h> #define FLASH_PAGE_SIZE 256 /* Flash Operating Commands */#define CMD_READ_ID 0x9f#define CMD_WRITE_ENABLE 0x06 #define CMD_BULK_ERASE 0xc7#define CMD_READ_BYTES 0x03#define CMD_PAGE_PROGRAM 0x02#define CMD_RDSR 0x05 /* Status Register bits. */#define SR_WIP 1 /* Write in progress */#define SR_WEL 2 /* Write enable latch */ /* ID Numbers */#define MANUFACTURER_ID 0x20#define DEVICE_ID 0x1120 /* Define max times to check status register before we give up. */#define MAX_READY_WAIT_COUNT 100000#define CMD_SZ 4 struct m25p10a {struct spi_device *spi;struct mutex lock;char erase_opcode;char cmd[ CMD_SZ ];}; /** Internal Helper functions */ /** Read the status register, returning its value in the location* Return the status register value.* Returns negative if error occurred.*/static int read_sr(struct m25p10a *flash){ssize_t retval;u8 code = CMD_RDSR;u8 val;retval = spi_write_then_read(flash->spi, &code, 1, &val, 1);if (retval < 0) {dev_err(&flash->spi->dev, "error %d reading SR\n", (int) retval);return retval;}return val;} /** Service routine to read status register until ready, or timeout occurs.* Returns non-zero if error.*/static int wait_till_ready(struct m25p10a *flash){int count;int sr;/* one chip guarantees max 5 msec wait here after page writes,* but potentially three seconds (!) after page erase.*/for (count = 0; count < MAX_READY_WAIT_COUNT; count++) {if ((sr = read_sr(flash)) < 0)break;else if (!(sr & SR_WIP))return 0;/* REVISIT sometimes sleeping would be best */} printk( "in (%s): count = %d\n", count );return 1;} /** Set write enable latch with Write Enable command.* Returns negative if error occurred.*/static inline int write_enable( struct m25p10a *flash ){flash->cmd[0] = CMD_WRITE_ENABLE;return spi_write( flash->spi, flash->cmd, 1 );} /** Erase the whole flash memory** Returns 0 if successful, non-zero otherwise.*/static int erase_chip( struct m25p10a *flash ){/* Wait until finished previous write command. */if (wait_till_ready(flash))return -1;/* Send write enable, then erase commands. */write_enable( flash );flash->cmd[0] = CMD_BULK_ERASE;return spi_write( flash->spi, flash->cmd, 1 );} /** Read an address range from the flash chip. The address range* may be any size provided it is within the physical boundaries.*/static int m25p10a_read( struct m25p10a *flash, loff_t from, size_t len, char *buf ){int r_count = 0, i;flash->cmd[0] = CMD_READ_BYTES;flash->cmd[1] = from >> 16;flash->cmd[2] = from >> 8;flash->cmd[3] = from;#if 1struct spi_transfer st[2];struct spi_message msg;spi_message_init( &msg );memset( st, 0, sizeof(st) );flash->cmd[0] = CMD_READ_BYTES;flash->cmd[1] = from >> 16;flash->cmd[2] = from >> 8;flash->cmd[3] = from;st[ 0 ].tx_buf = flash->cmd;st[ 0 ].len = CMD_SZ;spi_message_add_tail( &st[0], &msg );st[ 1 ].rx_buf = buf;st[ 1 ].len = len;spi_message_add_tail( &st[1], &msg );mutex_lock( &flash->lock );/* Wait until finished previous write command. */if (wait_till_ready(flash)) {mutex_unlock( &flash->lock );return -1;}spi_sync( flash->spi, &msg );r_count = msg.actual_length - CMD_SZ;printk( "in (%s): read %d bytes\n", __func__, r_count );for( i = 0; i < r_count; i++ ) {printk( "0x%02x\n", buf[ i ] );}mutex_unlock( &flash->lock );#endifreturn 0;} /** Write an address range to the flash chip. Data must be written in* FLASH_PAGE_SIZE chunks. The address range may be any size provided* it is within the physical boundaries.*/static int m25p10a_write( struct m25p10a *flash, loff_t to, size_t len, const char *buf ){int w_count = 0, i, page_offset;struct spi_transfer st[2];struct spi_message msg;#if 1if (wait_till_ready(flash)) { //读状态,等待readymutex_unlock( &flash->lock );return -1;}#endifwrite_enable( flash ); //写使能 spi_message_init( &msg );memset( st, 0, sizeof(st) );flash->cmd[0] = CMD_PAGE_PROGRAM;flash->cmd[1] = to >> 16;flash->cmd[2] = to >> 8;flash->cmd[3] = to;st[ 0 ].tx_buf = flash->cmd;st[ 0 ].len = CMD_SZ;spi_message_add_tail( &st[0], &msg );st[ 1 ].tx_buf = buf;st[ 1 ].len = len;spi_message_add_tail( &st[1], &msg );mutex_lock( &flash->lock );/* get offset address inside a page */page_offset = to % FLASH_PAGE_SIZE; /* do all the bytes fit onto one page? */if( page_offset + len <= FLASH_PAGE_SIZE ) { // yesst[ 1 ].len = len; printk("%d, cmd = %d\n", st[ 1 ].len, *(char *)st[0].tx_buf);//while(1){spi_sync( flash->spi, &msg );}w_count = msg.actual_length - CMD_SZ;}else { // no}printk( "in (%s): write %d bytes to flash in total\n", __func__, w_count );mutex_unlock( &flash->lock );return 0;}static int check_id( struct m25p10a *flash ) { char buf[10] = {0}; flash->cmd[0] = CMD_READ_ID;spi_write_then_read( flash->spi, flash->cmd, 1, buf, 3 ); printk( "Manufacture ID: 0x%x\n", buf[0] );printk( "Device ID: 0x%x\n", buf[1] | buf[2] << 8 );return buf[2] << 16 | buf[1] << 8 | buf[0]; } static int m25p10a_probe(struct spi_device *spi) { int ret = 0;struct m25p10a *flash;char buf[ 256 ];printk( "%s was called\n", __func__ );flash = kzalloc( sizeof(struct m25p10a), GFP_KERNEL );if( !flash ) {return -ENOMEM;}flash->spi = spi;mutex_init( &flash->lock );/* save flash as driver's private data */spi_set_drvdata( spi, flash );check_id( flash ); //读取ID#if 1ret = erase_chip( flash ); //擦除 if( ret < 0 ) {printk( "erase the entirely chip failed\n" );}printk( "erase the whole chip done\n" );memset( buf, 0x7, 256 );m25p10a_write( flash, 0, 20, buf); //0地址写入20个7memset( buf, 0, 256 );m25p10a_read( flash, 0, 25, buf ); //0地址读出25个数 #endifreturn 0; } static int m25p10a_remove(struct spi_device *spi) { return 0; } static struct spi_driver m25p10a_driver = { .probe = m25p10a_probe, .remove = m25p10a_remove, .driver = { .name = "m25p10a", }, }; static int __init m25p10a_init(void) { return spi_register_driver(&m25p10a_driver); } static void __exit m25p10a_exit(void) { spi_unregister_driver(&m25p10a_driver); } module_init(m25p10a_init); module_exit(m25p10a_exit); MODULE_DESCRIPTION("m25p10a driver for FS_S5PC100"); MODULE_LICENSE("GPL");
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