mini2440 sd卡加载过程详解
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最近在研究wifi模组, 是sdio接口的, 而手头刚好有一块mini2440,了解了一下sdio加载的过程, 发现和sd卡加载的过程是类似的。
这里用mini2440的内核源码, 来剖析一下sd卡的加载过程:
首先, mini2440内核加载的时候, 就会指定一部分设备初始化列表:
//---------------------------- arch/arm/mach-s3c2440/mach-mini2440.c ----------------------------///* devices we initialise */static struct platform_device *mini2440_devices[] __initdata = { &s3c_device_usb, &s3c_device_rtc, &s3c_device_lcd, &s3c_device_wdt, &s3c_device_i2c0, &s3c_device_iis, &mini2440_device_eth, &s3c24xx_uda134x, &s3c_device_nand, &s3c_device_sdi, // sd设备 &s3c_device_usbgadget,};/* MMC/SD */static struct s3c24xx_mci_pdata mini2440_mmc_cfg = { .gpio_detect = S3C2410_GPG(8), // 插入检测引脚 .gpio_wprotect = S3C2410_GPH(8), // 写保护引脚 .set_power = NULL, .ocr_avail = MMC_VDD_32_33|MMC_VDD_33_34, // 有效电压范围是3.2~3.3V, 3.3~3.4V};static void __init mini2440_machine_init(void){ s3c_device_sdi.dev.platform_data = &mini2440_mmc_cfg; platform_add_devices(mini2440_devices, ARRAY_SIZE(mini2440_devices)); }来看看s3c_device_sdi的定义:
//---------------------------- arch/arm/plat-s3c24xx/devs.c ----------------------------///* SDI */static struct resource s3c_sdi_resource[] = { [0] = { .start = S3C24XX_PA_SDI, .end = S3C24XX_PA_SDI + S3C24XX_SZ_SDI - 1, .flags = IORESOURCE_MEM, }, [1] = { .start = IRQ_SDI, .end = IRQ_SDI, .flags = IORESOURCE_IRQ, }};struct platform_device s3c_device_sdi = { .name = "s3c2410-sdi", .id = -1, .num_resources = ARRAY_SIZE(s3c_sdi_resource), .resource = s3c_sdi_resource,};有些人会奇怪, 我们这里不是在讲解2440吗, 为什么这里是s3c2410-sdi, 别急, 往下看:
//---------------------------- arch/arm/mach-s3c2440/mach-mini2440.c ----------------------------//static void __init mini2440_machine_init(void){ s3c_device_sdi.dev.platform_data = &mini2440_mmc_cfg; platform_add_devices(mini2440_devices, ARRAY_SIZE(mini2440_devices)); }//---------------------------- arch/arm/plat-s3c24xx/s3c244x.c ----------------------------//void __init s3c244x_map_io(void){ iotable_init(s3c244x_iodesc, ARRAY_SIZE(s3c244x_iodesc)); /* rename any peripherals used differing from the s3c2410 */ s3c_device_sdi.name = "s3c2440-sdi"; // 重命名为s3c2440-sdi s3c_device_i2c0.name = "s3c2440-i2c"; s3c_device_nand.name = "s3c2440-nand"; s3c_device_usbgadget.name = "s3c2440-usbgadget";}理解了吧?
接下来讲sd驱动的加载:
//---------------------------- drivers/mmc/host/s3cmci.c ----------------------------//static struct platform_device_id s3cmci_driver_ids[] = { { .name= "s3c2410-sdi", .driver_data= 0, }, { .name= "s3c2412-sdi", .driver_data= 1, }, { .name= "s3c2440-sdi", .driver_data= 1, // 下面会用到!!! }, { }};static struct platform_driver s3cmci_driver = { .driver= { .name= "s3c-sdi", .owner= THIS_MODULE, .pm= s3cmci_pm_ops, }, .id_table= s3cmci_driver_ids, .probe= s3cmci_probe, .remove= __devexit_p(s3cmci_remove), .shutdown= s3cmci_shutdown,};static int __init s3cmci_init(void){ return platform_driver_register(&s3cmci_driver);}module_init(s3cmci_init);驱动和设备匹配上的话,就会调用驱动的probe函数:
static int __devinit s3cmci_probe(struct platform_device *pdev){struct s3cmci_host *host;struct mmc_host*mmc; is2440 = platform_get_device_id(pdev)->driver_data; // 是否是2440, 这里就用到上面提到的driver_data, mmc = mmc_alloc_host(sizeof(struct s3cmci_host), &pdev->dev); // 分配mmc_host结构体 for (i = S3C2410_GPE(5); i <= S3C2410_GPE(10); i++) { // SDCLK SDCMD DATA0~DATA3 ret = gpio_request(i, dev_name(&pdev->dev)); // 申请gpio资源 if (ret) { dev_err(&pdev->dev, "failed to get gpio %d\n", i); for (i--; i >= S3C2410_GPE(5); i--) gpio_free(i); goto probe_free_host; } }host = mmc_priv(mmc); // 获取private域host->mmc = mmc;host->pdev= pdev;host->is2440= is2440;host->pdata = pdev->dev.platform_data; // 即上面提到的mini2440_mmc_cfgif (!host->pdata) {pdev->dev.platform_data = &s3cmci_def_pdata;host->pdata = &s3cmci_def_pdata;}if (is2440) {host->sdiimsk= S3C2440_SDIIMSK;host->sdidata= S3C2440_SDIDATA;host->clk_div= 1;} else {host->sdiimsk= S3C2410_SDIIMSK;host->sdidata= S3C2410_SDIDATA;host->clk_div= 2;} // 申请内存host->mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); // 这里会读取IORESOURCE_MEM域host->mem = request_mem_region(host->mem->start, resource_size(host->mem), pdev->name);host->base = ioremap(host->mem->start, resource_size(host->mem));host->irq = platform_get_irq(pdev, 0); // 这里会读取IORESOURCE_IRQ域, 返回start地址if (host->irq == 0) {dev_err(&pdev->dev, "failed to get interrupt resouce.\n");ret = -EINVAL;goto probe_iounmap;} // 申请中断,该中断为读写SD卡数据时所产生的中断if (request_irq(host->irq, s3cmci_irq, 0, DRIVER_NAME, host)) {dev_err(&pdev->dev, "failed to request mci interrupt.\n");ret = -ENOENT;goto probe_iounmap;} // 禁止上面所申请的中断 disable_irq(host->irq); host->irq_state = false;if (!host->pdata->no_detect) { // 如果SD控制器具有检测SD卡插拔状态的功能 ret = gpio_request(host->pdata->gpio_detect, "s3cmci detect"); // 申请插入检测io host->irq_cd = s3c2410_gpio_getirq(host->pdata->gpio_detect); if (host->irq_cd >= 0) { if (request_irq(host->irq_cd, s3cmci_irq_cd, // 注册插入检测中断处理函数, 申请中断,当有SD卡插入或拔出时,则进入该中断 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, DRIVER_NAME, host)) { dev_err(&pdev->dev, "can't get card detect irq.\n"); ret = -ENOENT; goto probe_free_gpio_cd; } } else { dev_warn(&pdev->dev, "host detect has no irq available\n"); gpio_direction_input(host->pdata->gpio_detect); } }if (!host->pdata->no_wprotect) { // 如果SD控制器具有写保护的功能ret = gpio_request(host->pdata->gpio_wprotect, "s3cmci wp"); // 申请写保护ioif (ret) {dev_err(&pdev->dev, "failed to get writeprotect\n");goto probe_free_irq_cd;}gpio_direction_input(host->pdata->gpio_wprotect);} if (s3cmci_host_usedma(host)) { // 如果使用dma ... } host->clk = clk_get(&pdev->dev, "sdi");ret = clk_enable(host->clk); // 使能clkhost->clk_rate = clk_get_rate(host->clk); // 通过时钟信号源获取时钟频率mmc->ops = &s3cmci_ops;mmc->ocr_avail= MMC_VDD_32_33 | MMC_VDD_33_34; // 默认是支持3.2~3.3V和3.3~3.4V#ifdef CONFIG_MMC_S3C_HW_SDIO_IRQmmc->caps= MMC_CAP_4_BIT_DATA | MMC_CAP_SDIO_IRQ; #elsemmc->caps= MMC_CAP_4_BIT_DATA;#endifmmc->f_min = host->clk_rate / (host->clk_div * 256);mmc->f_max = host->clk_rate / host->clk_div;if (host->pdata->ocr_avail)mmc->ocr_avail = host->pdata->ocr_avail; // 如果用户自定义了ocr_avail,即支持的工作电压,则使用自定义mmc->max_blk_count= 4095; // 一次请求的最大block数mmc->max_blk_size= 4095; // block的最大值mmc->max_req_size= 4095 * 512; // 一次请求的最大字节数mmc->max_seg_size= mmc->max_req_size; // 最大块大小mmc->max_phys_segs= 128;mmc->max_hw_segs= 128; ret = s3cmci_cpufreq_register(host); ret = mmc_add_host(mmc); // 将mmc_host添加进系统s3cmci_debugfs_attach(host); platform_set_drvdata(pdev, mmc); }其中:static struct mmc_host_ops s3cmci_ops = {.request= s3cmci_request, // 实现命令和数据的传输.set_ios= s3cmci_set_ios, // 设置硬件的IO, 包括工作电压等 .get_ro= s3cmci_get_ro, // 读取写保护的状态.get_cd= s3cmci_card_present, // 获取卡是否还存在的状态.enable_sdio_irq = s3cmci_enable_sdio_irq,};从对s3cmci_probe函数的分析可以看出,该函数除了对s3cmci_host和mmc_host这两个结构体赋值外,
最重要的工作就是调用了mmc_alloc_host函数和mmc_add_host函数。前者分配一个mmc_host,后者添加一个mmc_host。
下面我们就来介绍这两个函数,这两个函数都在drivers/mmc/core/host.c文件内。
//---------------------------- drivers/mmc/core/host.c ----------------------------//struct mmc_host *mmc_alloc_host(int extra, struct device *dev){ host = kzalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL); err = idr_get_new(&mmc_host_idr, host, &host->index); // 分配新的idr入口 dev_set_name(&host->class_dev, "mmc%d", host->index); // 设置设备的名字 host->parent = dev; host->class_dev.parent = dev; host->class_dev.class = &mmc_host_class; // 初始化设备结构体 device_initialize(&host->class_dev); spin_lock_init(&host->lock); init_waitqueue_head(&host->wq); // 初始化等待队列,工作队列 INIT_DELAYED_WORK(&host->detect, mmc_rescan); // 添加到等待队列 INIT_DELAYED_WORK_DEFERRABLE(&host->disable, mmc_host_deeper_disable); /* * By default, hosts do not support SGIO or large requests. * They have to set these according to their abilities. */ host->max_hw_segs = 1; host->max_phys_segs = 1; host->max_seg_size = PAGE_CACHE_SIZE; host->max_req_size = PAGE_CACHE_SIZE; host->max_blk_size = 512; host->max_blk_count = PAGE_CACHE_SIZE / 512; return host;}int mmc_add_host(struct mmc_host *host){ ...err = device_add(&host->class_dev);mmc_start_host(host); ...}在mmc_add_host函数内,调用mmc_start_host函数来启动SD:
//---------------------------- drivers/mmc/core/core.c ----------------------------//void mmc_start_host(struct mmc_host *host){ mmc_power_off(host); mmc_detect_change(host, 0);} static void mmc_power_off(struct mmc_host *host){ host->ios.clock = 0; host->ios.vdd = 0; if (!mmc_host_is_spi(host)) { host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN; host->ios.chip_select = MMC_CS_DONTCARE; } host->ios.power_mode = MMC_POWER_OFF; host->ios.bus_width = MMC_BUS_WIDTH_1; // 单线模式 host->ios.timing = MMC_TIMING_LEGACY; mmc_set_ios(host); // 设置工作电压和模式}void mmc_detect_change(struct mmc_host *host, unsigned long delay){ mmc_schedule_delayed_work(&host->detect, delay);}static int mmc_schedule_delayed_work(struct delayed_work *work, unsigned long delay){ return queue_delayed_work(workqueue, work, delay);}在mmc_start_host函数内调用mmc_detect_change函数来检测是否有SD卡已经插入。mmc_detect_change函数又调用mmc_schedule_delayed_work函数,mmc_schedule_delayed_work函数又调用了queue_delayed_work函数。
这样经过一段延时后,会执行在mmc_alloc_host函数中定义的工作队列(INIT_DELAYED_WORK(&host->detect,mmc_rescan);)所指向的mmc_rescan函数。
为什么要延时,这和按键去抖延时相类似。
下面我们来介绍mmc_rescan函数,它用来具体执行扫描并检测是否有SD卡插入的:
void mmc_rescan(struct work_struct *work){ struct mmc_host *host = container_of(work, struct mmc_host, detect.work);/* if there is a card registered, check whether it is still present */if ((host->bus_ops != NULL) && host->bus_ops->detect && !host->bus_dead)host->bus_ops->detect(host); // 如果已经注册过该卡,则检测卡是否还在/* if there still is a card present, stop here */ // host->bus_ops != NULL,说明这次mmc_rescan不是在上电初始化时调用的 // 所以不需要执行if后面的内容,要直接执行mmc_schedule_delayed_work函数if (host->bus_ops != NULL) { // 如果卡还在, 则直接退出mmc_bus_put(host);goto out;}/* detect a newly inserted card */ // 检测新插入的卡/* * Only we can add a new handler, so it's safe to * release the lock here. */mmc_bus_put(host);if (host->ops->get_cd && host->ops->get_cd(host) == 0) // 如果有插入检测引脚, 但是检测该引脚的状态是无卡,则退出goto out; // 判断当前mmc控制器是否被占用mmc_claim_host(host);mmc_power_up(host); // 上电mmc_go_idle(host); // 发送命令CMD0,使其处于IDLE状态mmc_send_if_cond(host, host->ocr_avail); // 发送SD_SEND_IF_COND命令,以支持SD2.0卡 // 依次探测SDIO、SD、MMC/* * First we search for SDIO... */err = mmc_send_io_op_cond(host, 0, &ocr);if (!err) {if (mmc_attach_sdio(host, ocr))mmc_power_off(host);goto out;}/* * ...then normal SD... */err = mmc_send_app_op_cond(host, 0, &ocr);if (!err) {if (mmc_attach_sd(host, ocr))mmc_power_off(host);goto out;}/* * ...and finally MMC. */err = mmc_send_op_cond(host, 0, &ocr);if (!err) {if (mmc_attach_mmc(host, ocr))mmc_power_off(host);goto out;}mmc_release_host(host);mmc_power_off(host);}我们以SDIO卡为例,因此会调用mmc_attach_sdio函数,它实现了SDIO卡的初始化:
//---------------------------- drivers/mmc/core/sd.c ----------------------------///* * Starting point for SD card init. */int mmc_attach_sd(struct mmc_host *host){int err;u32 ocr, rocr;err = mmc_send_app_op_cond(host, 0, &ocr);if (err)return err;mmc_sd_attach_bus_ops(host);if (host->ocr_avail_sd)host->ocr_avail = host->ocr_avail_sd;/* * We need to get OCR a different way for SPI. */if (mmc_host_is_spi(host)) {mmc_go_idle(host);err = mmc_spi_read_ocr(host, 0, &ocr);if (err)goto err;} // 设置电压,最终调用的是s3cmci_set_ios函数rocr = mmc_select_voltage(host, ocr);/* * Can we support the voltage(s) of the card(s)? */if (!rocr) {err = -EINVAL;goto err;} /* 检测和初始化卡 * Detect and init the card. * 在mmc_sd_init_card函数内,会通过发送一系列命令来启动SD卡,并得到寄存器CID,CSD,SCR,RCA等的数据。 */err = mmc_sd_init_card(host, rocr, NULL);if (err)goto err;mmc_release_host(host); /* 添加卡, 它通过调用device_add函数把mmc_card设备添加进系统中,并通知mmc块设备驱动。 * First add the card to the driver model... */err = mmc_add_card(host->card);mmc_claim_host(host);if (err)goto remove_card;return 0;remove_card:mmc_release_host(host);mmc_remove_card(host->card);host->card = NULL;mmc_claim_host(host);err:mmc_detach_bus(host);pr_err("%s: error %d whilst initialising SD card\n",mmc_hostname(host), err);return err;}static void mmc_sd_attach_bus_ops(struct mmc_host *host){const struct mmc_bus_ops *bus_ops;if (!mmc_card_is_removable(host))bus_ops = &mmc_sd_ops_unsafe;elsebus_ops = &mmc_sd_ops;mmc_attach_bus(host, bus_ops);}static const struct mmc_bus_ops mmc_sd_ops = {.remove = mmc_sd_remove, // 拔出sd卡的操作.detect = mmc_sd_detect, // 探测sd卡的操作.suspend = NULL,.resume = NULL,.power_restore = mmc_sd_power_restore,.alive = mmc_sd_alive,.shutdown = mmc_sd_suspend,};至此,mmc子系统的启动及检测SD卡设备就完成了。这个SD卡的检测是在上电之前就已插入插槽的,那么如果上电以后再把SD卡插入插槽中,系统又是如何检测的呢?
在前面介绍s3cmci_probe函数的时候,申请了两个中断,一个用于数据传输,另一个就是用于检测SD卡的。也就是当SD卡插入时,会引起相关引脚的电平变化,从而触发该中断,进入中断处理函数s3cmci_irq_cd:
//---------------------------- drivers\mmc\host/s3cmci.c ----------------------------//static irqreturn_t s3cmci_irq_cd(int irq, void *dev_id){ struct s3cmci_host *host = (struct s3cmci_host *)dev_id; dbg(host, dbg_irq, "card detect\n"); mmc_detect_change(host->mmc, msecs_to_jiffies(500)); return IRQ_HANDLED;}mmc_detect_change函数前面介绍过,它是用来检测是否存在SD卡。它的第二个参数表示延时的时间。在这里一定是要有延时的。
调用mmc_detect_change函数后所执行的内容与前面介绍的一样,这里就不再重复了。
无论是上电之前还是上电之后,SD卡的插入检测我们在上面都详细介绍完了,那么SD卡的拔出是如何检测的呢?当然一定是带电状态下才能检测SD卡的拔出的。
是回到mmc_rescan函数中:
void mmc_rescan(struct work_struct *work){ ... struct mmc_host *host = container_of(work, struct mmc_host, detect.work);/* if there is a card registered, check whether it is still present */if ((host->bus_ops != NULL) && host->bus_ops->detect && !host->bus_dead)host->bus_ops->detect(host); // 如果已经注册过该卡,则检测卡是否还在 ...}上面的语句就是用来检测SD卡的拔出的。我们在前面也已经介绍过了,在mmc_attach_bus函数内,把mmc_sd_ops赋给了host->bus_ops,
所以host->bus_ops->detect(host);实际回调的是mmc_sd_detect函数。
这里可能会有一个疑问:mmc_attach_bus函数是在mmc_rescan函数之后被调用的,那么就是说在mmc_rescan函数内,mmc_host->bus_ops还没有被赋值,
所以就不会回调mmc_sd_detect函数了。
我们要注意一点的是,mmc_rescan函数是在上电初始化过程中会被执行一次,因此在初始化的过程中完成了mmc_host->bus_ops的赋值。
而检测SD卡的拔出一定是在完成初始化以后,这时mmc_host->bus_ops已经被赋值,所以执行mmc_rescan函数中的
host->bus_ops->detect(host);语句不会出现任何问题。
我们来看看回调函数mmc_sd_detect,它定义在drivers/mmc/core/sd.c文件内:
/* * Card detection callback from host. */static void mmc_sd_detect(struct mmc_host *host){int err = 0;#ifdef CONFIG_MMC_PARANOID_SD_INITint retries = 5;#endifBUG_ON(!host);BUG_ON(!host->card);mmc_get_card(host->card);/* * Just check if our card has been removed. */#ifdef CONFIG_MMC_PARANOID_SD_INITwhile(retries) {err = mmc_send_status(host->card, NULL);if (err) {retries--;udelay(5);continue;}break;}if (!retries) {printk(KERN_ERR "%s(%s): Unable to re-detect card (%d)\n", __func__, mmc_hostname(host), err);}#elseerr = _mmc_detect_card_removed(host);#endifmmc_put_card(host->card);if (err) {mmc_sd_remove(host);mmc_claim_host(host);mmc_detach_bus(host);mmc_power_off(host);mmc_release_host(host);}}为什么要用给SD卡发送状态信息来判断SD卡是否存活(即是否被拔出)?因为当把SD卡拔出时,当然是得不到任何SD卡的信息,所以会出错。
我们再回到mmc_sdio_detect函数内,如果SD卡已拔出,mmc_select_card函数返回非零值,则执行下面的if里的内容。
下面我们来验证一下SD驱动。把SD卡插入开发板的插槽中,上电启动开发板,如果系统能够打印出类似下面的信息,则说明开发板能够识别出SD卡:
s3c-sdi s3c2440-sdi: running at 0kHz (requested: 0kHz).s3c-sdi s3c2440-sdi: running at 398kHz (requested: 400kHz).s3c-sdi s3c2440-sdi: running at 398kHz (requested: 400kHz).s3c-sdi s3c2440-sdi: running at 398kHz (requested: 400kHz).s3c-sdi s3c2440-sdi: running at 398kHz (requested: 400kHz).s3c-sdi s3c2440-sdi: running at 398kHz (requested: 400kHz).s3c-sdi s3c2440-sdi: running at 398kHz (requested: 400kHz).s3c-sdi s3c2440-sdi: running at 398kHz (requested: 400kHz).s3c-sdi s3c2440-sdi: running at 16875kHz (requested: 25000kHz).s3c-sdi s3c2440-sdi: running at 16875kHz (requested: 25000kHz).mmc0: new SDHC card at address aaaammcblk0: mmc0:aaaa SS08G 7.40 GiB mmcblk0: p1
如果先把开发板上电,然后再把SD卡插入插槽中,则系统也会自动打印出上面的信息。如果我们在带电的情况下把SD卡拔出,则系统会自动打印出类似下面的信息:
mmc0: card aaaa removeds3c-sdis3c2440-sdi: powered down.
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