從上一篇我們已經知道了SD卡涉及到的結構體以及SD的層次結構。現在首先從控制器驅動入手分析，以三星6410爲例。
以平臺驅動的方式註冊控制器驅動
static int __init sdhci_s3c_init(void)
{
return platform_driver_register(&sdhci_s3c_driver);
}
static void __exit sdhci_s3c_exit(void)
{
platform_driver_unregister(&sdhci_s3c_driver);
}
module_init(sdhci_s3c_init);
module_exit(sdhci_s3c_exit);
static struct platform_driver sdhci_s3c_driver = {
.probe = sdhci_s3c_probe,
.remove = __devexit_p(sdhci_s3c_remove),
.suspend = sdhci_s3c_suspend,
.resume = sdhci_s3c_resume,
.driver = {
.owner = THIS_MODULE,
.name = "s3c-sdhci",
},
};
當匹配成功後，進入sdhci_s3c_probe函數
static int __devinit sdhci_s3c_probe(struct platform_device *pdev)
{
……..
struct sdhci_host *host;
host = sdhci_alloc_host(dev, sizeof(struct sdhci_s3c));
ret = sdhci_add_host(host);//完成SDHCI和MMC相關匹配參數以及sdhci_ops的配置
……..
}
int sdhci_add_host(struct sdhci_host *host)
{
………
tasklet_init(&host->card_tasklet,
sdhci_tasklet_card, (unsigned long)host);
tasklet_init(&host->finish_tasklet,
sdhci_tasklet_finish, (unsigned long)host);
ret = request_irq(host->irq, sdhci_irq, IRQF_SHARED,
mmc_hostname(mmc), host);
if (ret)
goto untasklet;
………
}
在中斷處理例程中，首先讀取SD卡額狀態，根據不同的狀態完成不同的操作
static irqreturn_t sdhci_irq(int irq, void *dev_id)
{
………
intmask = sdhci_readl(host, SDHCI_INT_STATUS);
if (!intmask || intmask == 0xffffffff) {
result = IRQ_NONE;
goto out;
}
DBG("*** %s got interrupt: 0x%08x\n",
mmc_hostname(host->mmc), intmask);
if (intmask & (SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE)) {
sdhci_writel(host, intmask & (SDHCI_INT_CARD_INSERT |
SDHCI_INT_CARD_REMOVE), SDHCI_INT_STATUS);
tasklet_schedule(&host->card_tasklet);
}
intmask &= ~(SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE);
if (intmask & SDHCI_INT_CMD_MASK) {
sdhci_writel(host, intmask & SDHCI_INT_CMD_MASK,
SDHCI_INT_STATUS);
sdhci_cmd_irq(host, intmask & SDHCI_INT_CMD_MASK);
}
if (intmask & SDHCI_INT_DATA_MASK) {
sdhci_writel(host, intmask & SDHCI_INT_DATA_MASK,
SDHCI_INT_STATUS);
sdhci_data_irq(host, intmask & SDHCI_INT_DATA_MASK);
}
intmask &= ~(SDHCI_INT_CMD_MASK | SDHCI_INT_DATA_MASK);
intmask &= ~SDHCI_INT_ERROR;
if (intmask & SDHCI_INT_BUS_POWER) {
printk(KERN_ERR "%s: Card is consuming too much power!\n",
mmc_hostname(host->mmc));
sdhci_writel(host, SDHCI_INT_BUS_POWER, SDHCI_INT_STATUS);
}
……..
}
通過sdhci_cmd_irq和sdhci_data_irq發送命令和數據，如果狀態時有SD卡插入或拔出，我們將進入任務調度host->card_tasklet，調度器的初始化在sdhci_add_host中
static void sdhci_tasklet_card(unsigned long param)
{
struct sdhci_host *host;
unsigned long flags;
host = (struct sdhci_host*)param;
spin_lock_irqsave(&host->lock, flags);
if (!(sdhci_readl(host, SDHCI_PRESENT_STATE) & SDHCI_CARD_PRESENT)) {
if (host->mrq) {
printk(KERN_ERR "%s: Card removed during transfer!\n",
mmc_hostname(host->mmc));
printk(KERN_ERR "%s: Resetting controller.\n",
mmc_hostname(host->mmc));
sdhci_reset(host, SDHCI_RESET_CMD);
sdhci_reset(host, SDHCI_RESET_DATA);
host->mrq->cmd->error = -ENOMEDIUM;
tasklet_schedule(&host->finish_tasklet);
}
}
spin_unlock_irqrestore(&host->lock, flags);
mmc_detect_change(host->mmc, msecs_to_jiffies(200));
}
在任務調度裏面首先還是判斷卡和控制器的狀態，然後調用mmc_detect_change做一個延時操作後調用mmc_schedule_delayed_work
void mmc_detect_change(struct mmc_host *host, unsigned long delay)
{
#ifdef CONFIG_MMC_DEBUG
unsigned long flags;
spin_lock_irqsave(&host->lock, flags);
WARN_ON(host->removed);
spin_unlock_irqrestore(&host->lock, flags);
#endif
mmc_schedule_delayed_work(&host->detect, delay);
}
host->detect工作隊列在mmc_alloc_host中初始化
INIT_DELAYED_WORK(&host->detect, mmc_rescan);
當有卡插入的時候，進入控制器中斷處理函數，處理工作隊列，最後調用mmc_rescan，進入core層。
void mmc_rescan(struct work_struct *work)
{
…….
struct mmc_host *host =
container_of(work, struct mmc_host, detect.work);//得到mmc_host的數據
if (host->rescan_disable)
return;
mmc_bus_get(host);
/*
* if there is a _removable_ card registered, check whether it is
* still present
*/
if (host->bus_ops && host->bus_ops->detect && !host->bus_dead
&& !(host->caps & MMC_CAP_NONREMOVABLE))
host->bus_ops->detect(host);
/*
* Let mmc_bus_put() free the bus/bus_ops if we've found that
* the card is no longer present.
*/
mmc_bus_put(host);
mmc_bus_get(host);
/* if there still is a card present, stop here */
if (host->bus_ops != NULL) {
mmc_bus_put(host);
goto out;
}
/*
* 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)
goto out;
mmc_claim_host(host);
for (i = 0; i < ARRAY_SIZE(freqs); i++) {
if (!mmc_rescan_try_freq(host, max(freqs[i], host->f_min)))
break;
if (freqs[i] < host->f_min)
break;
}
mmc_release_host(host);
out:
if (host->caps & MMC_CAP_NEEDS_POLL)
mmc_schedule_delayed_work(&host->detect, HZ);
}