spi驱动分析

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转载的地址：http://www.diybl.com/course/6_system/linux/Linuxjs/200868/123621.html

今天折腾了一天的SPI设备的驱动加载，甚至动用了逻辑分析仪来查看spi总线的波形，主要包括两个SPI设备，at45db321d和mcp2515，一个是串行的dataflash，一个是can总线设备芯片。前者对于我们来说非常重要，我们可以借助该设备对uboot和kernel以及根文件系统进行更新。
??? 预备知识：设备和驱动是如何匹配的？系统的热插拔是如何实现的？
??? 首先一点，设备和驱动是严格区分的，设备是设备，驱动是驱动，设备通过struct device来定义，当然用户也可以将该结构体封装到自己定义的device结构体中，例如，struct platform_device，这是我们采用platform_bus_type总线的设备定义的结构体形式：

include/linux/platform_device.h文件中:
struct platform_device {
??? const char??? * name;
??? u32??? ??? id;
??? struct device??? dev;
??? u32??? ??? num_resources;
??? struct resource??? * resource;
};
只要是9260的外围模块，就像IIC硬件控制器,SPI硬件控制器，都被完全的定义成这种结构体的格式，这种结构体主要包含了硬件资源和名称，硬件资源分为寄存器和IRQ两种。platform_device通过向内核注册struct device dev这个结构体来告诉内核加载这个设备，
??? 方法就是? device_register(&platform_device->dev) ?
内核不关心你使用的是platform_device还是spi_device，内核只关心你的struct device结构体，内核通过这个struct device结构体自然能够顺藤摸瓜找到你是platform_device还是spi_device，这就是linux最引以为傲的contian_of()大法。

驱动通过struct driver这个结构体来定义，与struct device一致，你也可以用自己的结构体去封装：例如，struct platform_driver。
include/linux/platform_device.h文件中:

struct platform_driver {
??? int (*probe)(struct platform_device *);
??? int (*remove)(struct platform_device *);
??? void (*shutdown)(struct platform_device *);
??? int (*suspend)(struct platform_device *,pm_message_t state);
??? int (*suspend_late)(struct platform_device *,pm_message_t state);
??? int (*resume_early)(struct platform_device *);
??? int (*resume)(struct platform_device *);
??? struct device_driver driver;
};
与device一致，应用程序通过driver_register(&platform_driver->driver)向内核中注册你当前的驱动，而内核不关心你封装成的结构，而内核搜索的方法还是同样的contain_of大法。



系统如何将这两者匹配上的？而不会将iic的设备加载到spi的驱动上面？不会将这个iic设备的驱动加载到那个iic设备上，设备和驱动之间是如何联系的？总线，这就是总线的作用！
include/linux/device.h文件中有总线类型的定义。
struct bus_type {
??? const char??? ??? * name;

??? struct subsystem??? 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;

??? 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);
};
这个总线设备中最重要的可能是match成员，由于我们一般很少去建立一个新的总线，所以我们很少涉及总线的编程，我们就只关注我们所关注的。
总线如何将两者关联起来，热插拔大家知道吧，当一个设备被通过device_register注册到内核中时，会导致一个热插拔事件产生，系统会遍历该总线上的所有驱动程序，调用bus的match算法，来寻找与该设备相匹配的驱动程序，当一个驱动注册到内核的时候，处理过程与此相似（这是我理解的阿，大家批评指正），而一般的macth算法都比较简单，例如platform_bus的匹配算法就很简单，就是比较platform_device和platform_driver的name成员，如果匹配成功，就加载相应的设备或者驱动！这就完成了一个连接的过程。。。



那么这两种设备驱动中最重要的类型在linux中如何表现出来，那我们就有必要介绍一下从2.6开始实现的sys文件系统了，

/sys/bus $ cat /etc/fstab
proc??????????? /proc?? proc??? defaults??? 0?? 0
devpts?? /dev/pts?? devpts? defaults?? 0 0
tmpfs?????????? /dev/shm???????? tmpfs? defaults??????? 0?????? 0
sysfs?????????? /sys???????????? sysfs????????? defaults??????? 0?????? 0
/dev/mtdblock2? /mnt/flash2???? yaffs?? defaults??????? 0?????? 0

加载这个文件系统对于我们分析设备模型是非常有好处的。
sys文件夹下一般有如下的目录：
/sys $ ls -al
drwxr-xr-x?? 10 root???? root??????????? 0 Jan? 1? 1970 .
drwxrwxrwx?? 11 1000???? tao????????? 4096 May 22 06:56 ..
drwxr-xr-x??? 7 root???? root??????????? 0 Oct 27 14:09 block
drwxr-xr-x??? 8 root???? root??????????? 0 Jan? 1? 1970 bus
drwxr-xr-x?? 21 root???? root??????????? 0 Jan? 1? 1970 class
drwxr-xr-x??? 4 root???? root??????????? 0 Jan? 1? 1970 devices
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 firmware
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 fs
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 kernel
drwxr-xr-x?? 22 root???? root??????????? 0 Oct 27 14:10 module
block是由于历史原因形成的block设备的文件夹。我们关心的是bus文件夹。
我们以spi设备为例：spi部分要包括两种设备，一种是platform_device，一种是spi_device。
在arch/arm/mach-at91/at91sam9260_device.c文件中，定义的SPI硬件控制模块设备，这我们不需要关心。
还有一种是spi_device，定义在arch/arm/mach-at91/board-sam9260ek.c文件中，这就是我们的dataflash和mcp2515设备，
所以如何设备加载成功的话，在bus下面的每个目录里面，都存在devices和drivers两个文件夹，分别对应设备和文件。
/sys/bus/platform/devices $ ls -al
drwxr-xr-x??? 2 root???? root??????????? 0 Oct 27 16:01 .
drwxr-xr-x??? 4 root???? root??????????? 0 Jan? 1? 1970 ..
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 at91_i2c -> ../../../devices/platform/at91_i2c
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 at91_nand -> ../../../devices/platform/at91_nand
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 at91_ohci -> ../../../devices/platform/at91_ohci
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 atmel_spi.0 -> ../../../devices/platform/atmel_spi.0
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 atmel_spi.1 -> ../../../devices/platform/atmel_spi.1
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 atmel_usart.0 -> ../../../devices/platform/atmel_usart.0
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 atmel_usart.1 -> ../../../devices/platform/atmel_usart.1
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 atmel_usart.2 -> ../../../devices/platform/atmel_usart.2
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:01 macb -> ../../../devices/platform/macb
驱动
/sys/bus/platform/drivers/atmel_spi $ ls -al
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 .
drwxr-xr-x??? 8 root???? root??????????? 0 Jan? 1? 1970 ..
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:10 atmel_spi.0 -> ../../../../devices/platform/atmel_spi.0
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 16:10 atmel_spi.1 -> ../../../../devices/platform/atmel_spi.1
--w-------??? 1 root???? root???????? 4096 Oct 27 16:10 bind
--w-------??? 1 root???? root???????? 4096 Oct 27 16:10 unbind
如果出现上面的这个情况，说明你的设备（两路spi总线）和驱动都加载成功了，如果你的devices下面没有spi.0设备和spi.1设备的话，说明
board-sam9260ek.c文件中的这个函数出错：
static void __init ek_board_init(void)
{
??? /* Serial */
??? at91_add_device_serial();
??? /* USB Host */
??? at91_add_device_usbh(&ek_usbh_data);
??? /* USB Device */
??? at91_add_device_udc(&ek_udc_data);
??? /* SPI */
??? at91_add_device_spi(ek_spi_devices,ARRAY_SIZE(ek_spi_devices));
??? /* NAND */
??? at91_add_device_nand(&ek_nand_data);
??? /* Ethernet */
??? at91_add_device_eth(&ek_macb_data);
??? /* MMC */
??? at91_add_device_mmc(0,&ek_mmc_data);
??? /* I2C */
??? at91_add_device_i2c();
}
这里是设备注册的地方，我们还应该在下面这个目录下看到这两个文件。
/sys/bus/spi/devices $ ls -al
drwxr-xr-x??? 2 root???? root??????????? 0 Oct 27 14:09 .
drwxr-xr-x??? 4 root???? root??????????? 0 Jan? 1? 1970 ..
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 14:09 spi0.1 -> ../../../devices/platform/atmel_spi.0/spi0.1
lrwxrwxrwx??? 1 root???? root??????????? 0 Oct 27 14:09 spi1.0 -> ../../../devices/platform/atmel_spi.1/spi1.0
这两个链接说明我们的两个spi设备注册都被接受了，剩下来就是驱动的问题。有人看不懂这个sys文件系统的层次关系，其实这里比较好说明，就是spi0.1是atmel_spi.0设备的子设备嘛，很好理解的。

驱动：
platform_driver驱动：
/sys/bus/platform/drivers $ ls -al
drwxr-xr-x??? 8 root???? root??????????? 0 Jan? 1? 1970 .
drwxr-xr-x??? 4 root???? root??????????? 0 Jan? 1? 1970 ..
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 at91_i2c
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 at91_nand
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 at91_ohci
drwxr-xr-x??? 2 root???? root??????????? 0 Oct 27 16:10 atmel_spi
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 atmel_usart
drwxr-xr-x??? 2 root???? root??????????? 0 Jan? 1? 1970 macb
我们可以看到这个驱动只有一个atmel_spi，这个驱动是在哪加载的？
driver/spi/atmel_spi.c文件加载的。

spi_driver驱动：
/sys/bus/spi/drivers $ ls -al
drwxr-xr-x??? 4 root???? root??????????? 0 Oct 27 14:10 .
drwxr-xr-x??? 4 root???? root??????????? 0 Jan? 1? 1970 ..
drwxr-xr-x??? 2 root???? root??????????? 0 Oct 27 14:10 mcp2515
drwxr-xr-x??? 2 root???? root??????????? 0 Oct 27 14:09 mtd_dataflash
这是我们加载的两个驱动，说明驱动也加载正常了。

下面我们来说说我们遇到的问题吧。
在设备和驱动都加载正常之后，出现与dataflash设备通信不上的情况，驱动加载的时候，读取芯片的状态字读出是0xff，说明工作不正常，动用逻辑分析仪监控spi总线的通信，意外的发现，sck信号和cs信号正常，但是mosi无信号输出，开始觉得可能是spi总线适配器有问题，后来仔细观察原理图之后，发现dataflash和mmc／sd是使用同样的io口的，即pa0,pa1,pa2，而我的内核配置中打开了对mmc的支持，所以导致mosi不正常，所以可能9260的mmc与dataflash不能同时使用，但9263的可以。
解决办法：make menuconfig
Device Drivers--->MMC/SD card support，取消其支持，问题解决！

?

?/* setup spi core then atmel-specific driver state */ ??? ret = -ENOMEM; ??? master = spi_alloc_master(&pdev->dev,sizeof *as); ??? if (!master) ??? ??? goto out_free; ??? master->bus_num = pdev->id; ??? master->num_chipselect = 4; ??? master->setup = atmel_spi_setup; ??? master->transfer = atmel_spi_transfer; ??? master->cleanup = atmel_spi_cleanup; ??? platform_set_drvdata(pdev,master); ??? as = spi_master_get_devdata(master); ??? as->buffer = dma_alloc_coherent(&pdev->dev,BUFFER_SIZE,??? ??? ??? ??? ??? &as->buffer_dma,GFP_KERNEL); ??? if (!as->buffer) ??? ??? goto out_free; ??? spin_lock_init(&as->lock); ??? INIT_LIST_HEAD(&as->queue); ??? as->pdev = pdev; ??? as->regs = ioremap(regs->start,(regs->end - regs->start) + 1); ??? if (!as->regs) ??? ??? goto out_free_buffer; ??? as->irq = irq; ??? as->clk = clk; #ifdef CONFIG_ARCH_AT91 ??? if (!cpu_is_at91rm9200()) ??? ??? as->new_1 = 1; #endif ??? ret = request_irq(irq,atmel_spi_interrupt,??? ??? ??? pdev->dev.bus_id,master); ??? if (ret) ??? ??? goto out_unmap_regs; ??? /* Initialize the hardware */ ??? clk_enable(clk); ??? spi_writel(as,CR,SPI_BIT(SWRST)); ??? spi_writel(as,MR,SPI_BIT(MSTR) | SPI_BIT(MODFDIS)); ??? spi_writel(as,PTCR,SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS)); ??? spi_writel(as,SPI_BIT(SPIEN)); ??? /* go! */ ??? dev_info(&pdev->dev,"Atmel SPI Controller at 0x%08lx (irq %d)n",??? ??? ??? (unsigned long)regs->start,irq); ??? /*spi注册这个主控制器*/ ??? ret = spi_register_master(master); ??? if (ret) ??? ??? goto out_reset_hw; ??? return 0; out_reset_hw: ??? spi_writel(as,SPI_BIT(SWRST)); ??? clk_disable(clk); ??? free_irq(irq,master); out_unmap_regs: ??? iounmap(as->regs); out_free_buffer: ??? dma_free_coherent(&pdev->dev,as->buffer,??? ??? ??? as->buffer_dma); out_free: ??? clk_put(clk); ??? spi_master_put(master); ??? return ret; } 而这个spi_register_master位于driver/spi/spi.c文件中，该函数调用了scan_boardinfo(master)，扫描该spi master下面设备。该函数就存在于该文件下：该函数调用了spi_new_device(master,chip)，这个chip就是一个spi_board_info结构体，这就是at91_add_device_spi第一个作用的用处：向内核的链表注册spi_board_info结构体的用处所在。我们来看函数的调用过程： atmel_spi_probe----->spi_register_master----->scan_boardinfo ---->spi_new_device 我们来看这个spi_new_device函数： struct spi_device *spi_new_device(struct spi_master *master,??? ??? ??? ??? ? struct spi_board_info *chip) { ??? struct spi_device??? *proxy; ??? struct device??? ??? *dev = master->cdev.dev; ??? int??? ??? ??? status; ??? /* NOTE:? caller did any chip->bus_num checks necessary */ ??? if (!spi_master_get(master)) ??? ??? return NULL; ??? /*靠，终于找到你了，先暴打一顿，舒服了。。这里就分配了我们重要的spi_device结构体*/ ??? proxy = kzalloc(sizeof *proxy,GFP_KERNEL); ??? if (!proxy) { ??? ??? dev_err(dev,"can't alloc dev for cs%dn",??? ??? ??? chip->chip_select); ??? ??? goto fail; ??? } /*这就是将我们的信息体中的数据转化为spi_device识别的数据*/ ??? proxy->master = master; ??? proxy->chip_select = chip->chip_select; ??? proxy->max_speed_hz = chip->max_speed_hz; ??? proxy->mode = chip->mode; ??? proxy->irq = chip->irq; ??? proxy->modalias = chip->modalias; ??? snprintf(proxy->dev.bus_id,sizeof proxy->dev.bus_id,??? ??? ??? "%s.%u",master->cdev.class_id,??? ??? ??? chip->chip_select); ??? proxy->dev.parent = dev; ??? proxy->dev.bus = &spi_bus_type; ??? /*这里很重要，如果你的spi设备是dataflash的话，保存的就是你的分区表！！！所以我们要返回去修改我们的spi_boardinfo结构体*/ ??? proxy->dev.platform_data = (void *) chip->platform_data; ??? /*片选信号*/ ??? proxy->controller_data = chip->controller_data; ??? proxy->controller_state = NULL; ??? proxy->dev.release = spidev_release; ??? /* drivers may modify this default i/o setup */ ??? status = master->setup(proxy); ??? if (status < 0) { ??? ??? dev_dbg(dev,"can't %s %s,status %dn",??? ??? ??? ??? "setup",proxy->dev.bus_id,status); ??? ??? goto fail; ??? } ??? /* driver core catches callers that misbehave by defining ??? ?* devices that already exist. ??? ?*/ ??? /*看到这句话，大家放心了吧，大家也就知道怎么找到spi_driver驱动的。。。*/ ??? status = device_register(&proxy->dev); ??? if (status < 0) { ??? ??? dev_dbg(dev,??? ??? ??? ??? "add",status); ??? ??? goto fail; ??? } ??? dev_dbg(dev,"registered child %sn",proxy->dev.bus_id); ??? return proxy; fail: ??? spi_master_put(master); ??? kfree(proxy); ??? return NULL; } 下面我们要解决最后的一个问题，dataflash的分区的问题，看了这么多，大家应该知道怎么解决了吧！ 我们看mtd_dataflash.c文件中驱动加载函数调用了下面这个函数来添加flash设备。。 static int __devinit add_dataflash(struct spi_device *spi,char *name,??? ??? int nr_pages,int pagesize,int pageoffset) { ??? struct dataflash??? ??? *priv; ??? struct mtd_info??? ??? ??? *device; ??? /*这里就告诉我们要在spi_boardinfo结构体的platform_data成员指向一个我们需要的flash_platform_data数据！*/ ??? struct flash_platform_data??? *pdata = spi->dev.platform_data; ??? priv = kzalloc(sizeof *priv,GFP_KERNEL); ??? if (!priv) ??? ??? return -ENOMEM; ??? init_MUTEX(&priv->lock); ??? priv->spi = spi; ??? priv->page_size = pagesize; ??? priv->page_offset = pageoffset; ??? /* name must be usable with cmdlinepart */ ??? sprintf(priv->name,"spi%d.%d-%s",??? ??? ??? spi->master->bus_num,spi->chip_select,??? ??? ??? name); ??? device = &priv->mtd; ??? device->name = (pdata && pdata->name) ? pdata->name : priv->name; ??? device->size = nr_pages * pagesize; ??? device->erasesize = pagesize; ??? device->writesize = pagesize; ??? device->owner = THIS_MODULE; ??? device->type = MTD_DATAFLASH; ??? device->flags = MTD_WRITEABLE; ??? device->erase = dataflash_erase; ??? device->read = dataflash_read; ??? device->write = dataflash_write; ??? device->priv = priv; ??? dev_info(&spi->dev,"%s (%d KBytes)n",name,device->size/1024); ??? dev_set_drvdata(&spi->dev,priv); ??? if (mtd_has_partitions()) { ??? ??? struct mtd_partition??? *parts; ??? ??? int??? ??? ??? nr_parts = 0; ??? /*我们这里没有定义该宏，所以不会在命令行传递分区表*/ #ifdef CONFIG_MTD_CMDLINE_PARTS ??? ??? static const char *part_probes[] = { "cmdlinepart",NULL,}; ??? ??? nr_parts = parse_mtd_partitions(device,part_probes,&parts,0); #endif ??? ??? if (nr_parts <= 0 && pdata && pdata->parts) { ??? ??? ??? parts = pdata->parts; ??? ??? ??? nr_parts = pdata->nr_parts; ??? ??? } ??? ??? if (nr_parts > 0) { ??? ??? ??? priv->partitioned = 1; ??? ??? ??? return add_mtd_partitions(device,parts,nr_parts); ??? ??? } ??? } else if (pdata && pdata->nr_parts) ??? ??? dev_warn(&spi->dev,"ignoring %d default partitions on %sn",??? ??? ??? ??? pdata->nr_parts,device->name); ??? return add_mtd_device(device) == 1 ? -ENODEV : 0; } 所以我们需要修改这个文件： arch/arm/mach-at91/board-sam9260ek.c文件： 添加如下： #if? !defined(CONFIG_MMC_AT91) #define??? SIZE_1PAGE??? 528 #define??? SIZE_1M (unsigned long)(1024*1024) static struct mtd_partition ek_dataflash_partition[] = { ??? { ??? ??? .name??? = "U-boot ENV",??? ??? .offset??? = 0,??? ??? .size??? = 64*SIZE_1PAGE,??? { ??? ??? .name??? = "U-BOOT",??? ??? .offset??? = 64*SIZE_1PAGE,??? ??? .size??? = 400*SIZE_1PAGE,??? { ??? ??? .name ="Kernel",??? ??? .offset=464*SIZE_1PAGE,??? ??? .size??? = 4000*SIZE_1PAGE,??? { ??? ??? .name ="Root fs",??? ??? .offset=4464*SIZE_1PAGE,??? ??? .size??? = (8192-4464)*SIZE_1PAGE,}; struct flash_platform_data dataflash_atmel={ ??? .name="AT45DB321",??? .parts=ek_dataflash_partition,??? .nr_parts=ARRAY_SIZE(ek_dataflash_partition),}; #endif 修改spi_boardinfo结构体： static struct spi_board_info ek_spi_devices[] = { #if !defined(CONFIG_MMC_AT91) ??? {??? /* DataFlash chip */ ??? ??? .modalias??? = "mtd_dataflash",??? ??? .platform_data=&dataflash_atmel,添加platform_data结构成员。 这里我们建立mtd_partition结构体要注意，由于dataflash是以528字节每页的，其实，at45db321x芯片可以设置为512字节每页，这个操作是不可以逆转的，那个位是一个otp位，用过的人就应该知道，但是出厂的时候默认的528字节每页。 如果我们不是以528个字节为单位的话，内核将出警告，强制将分区加载为readonly格式。 到此，分区加载成功，dmesg输出如下信息： <6>mtd_dataflash spi0.1: AT45DB321x (4224 KBytes) <5>Creating 4 MTD partitions on "AT45DB321": <5>0x00000000-0x00008400 : "U-boot ENV" <5>0x00008400-0x0003bd00 : "U-BOOT" <5>0x0003bd00-0x0023f700 : "Kernel" <5>0x0023f700-0x00420000 : "Root fs" linux简直太伟大了，使用得越多，就越能体会到其思想的伟大！灵活！?