三星平臺SD/MMC驅動分析

三星平臺SD/MMC驅動主要有兩個文件sdhci.c和sdhci-s3c.c,核心驅動在後者裏面。

我們一步一步分析，先從平臺驅動註冊看起

sdhci-s3c.c:

static int __init sdhci_s3c_init(void)
{
	return platform_driver_register(&sdhci_s3c_driver);
}

註冊了sdhci-s3c-driver，看下該結構體定義：

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",
	},
};

看重點——probe函數：

static int __devinit sdhci_s3c_probe(struct platform_device *pdev)
{
	struct s3c_sdhci_platdata *pdata = pdev->dev.platform_data;
	struct device *dev = &pdev->dev;
	struct sdhci_host *host;
	struct sdhci_s3c *sc;
	struct resource *res;
	int ret, irq, ptr, clks;

	if (!pdata) {
		dev_err(dev, "no device data specified\n");
		return -ENOENT;
	}

	irq = platform_get_irq(pdev, 0);
	if (irq < 0) {
		dev_err(dev, "no irq specified\n");
		return irq;
	}

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		dev_err(dev, "no memory specified\n");
		return -ENOENT;
	}

	host = sdhci_alloc_host(dev, sizeof(struct sdhci_s3c));
	if (IS_ERR(host)) {
		dev_err(dev, "sdhci_alloc_host() failed\n");
		return PTR_ERR(host);
	}

	sc = sdhci_priv(host);

	sc->host = host;
	sc->pdev = pdev;
	sc->pdata = pdata;
	sc->ext_cd_gpio = -1; /* invalid gpio number */

	platform_set_drvdata(pdev, host);

	sc->clk_io = clk_get(dev, "hsmmc");
	if (IS_ERR(sc->clk_io)) {
		dev_err(dev, "failed to get io clock\n");
		ret = PTR_ERR(sc->clk_io);
		goto err_io_clk;
	}

	/* enable the local io clock and keep it running for the moment. */
	clk_enable(sc->clk_io);

	for (clks = 0, ptr = 0; ptr < MAX_BUS_CLK; ptr++) {
		struct clk *clk;
		char *name = pdata->clocks[ptr];

		if (name == NULL)
			continue;

		clk = clk_get(dev, name);
		if (IS_ERR(clk)) {
			dev_err(dev, "failed to get clock %s\n", name);
			continue;
		}

		clks++;
		sc->clk_bus[ptr] = clk;

		/*
		 * save current clock index to know which clock bus
		 * is used later in overriding functions.
		 */
		sc->cur_clk = ptr;

		clk_enable(clk);

		dev_info(dev, "clock source %d: %s (%ld Hz)\n",
			 ptr, name, clk_get_rate(clk));
	}

	if (clks == 0) {
		dev_err(dev, "failed to find any bus clocks\n");
		ret = -ENOENT;
		goto err_no_busclks;
	}

	sc->ioarea = request_mem_region(res->start, resource_size(res),
					mmc_hostname(host->mmc));
	if (!sc->ioarea) {
		dev_err(dev, "failed to reserve register area\n");
		ret = -ENXIO;
		goto err_req_regs;
	}

	host->ioaddr = ioremap_nocache(res->start, resource_size(res));
	if (!host->ioaddr) {
		dev_err(dev, "failed to map registers\n");
		ret = -ENXIO;
		goto err_req_regs;
	}

	/* Ensure we have minimal gpio selected CMD/CLK/Detect */
	if (pdata->cfg_gpio)
		pdata->cfg_gpio(pdev, pdata->max_width);

	host->hw_name = "samsung-hsmmc";
	host->ops = &sdhci_s3c_ops;
	host->quirks = 0;
	host->irq = irq;

	/* Setup quirks for the controller */
	host->quirks |= SDHCI_QUIRK_NO_ENDATTR_IN_NOPDESC;
	host->quirks |= SDHCI_QUIRK_NO_HISPD_BIT;

#ifndef CONFIG_MMC_SDHCI_S3C_DMA

	/* we currently see overruns on errors, so disable the SDMA
	 * support as well. */
	host->quirks |= SDHCI_QUIRK_BROKEN_DMA;

#endif /* CONFIG_MMC_SDHCI_S3C_DMA */

	/* It seems we do not get an DATA transfer complete on non-busy
	 * transfers, not sure if this is a problem with this specific
	 * SDHCI block, or a missing configuration that needs to be set. */
	host->quirks |= SDHCI_QUIRK_NO_BUSY_IRQ;

	if (pdata->cd_type == S3C_SDHCI_CD_NONE ||
	    pdata->cd_type == S3C_SDHCI_CD_PERMANENT)
		host->quirks |= SDHCI_QUIRK_BROKEN_CARD_DETECTION;

	if (pdata->cd_type == S3C_SDHCI_CD_PERMANENT)
		host->mmc->caps = MMC_CAP_NONREMOVABLE;

	if (pdata->host_caps)
		host->mmc->caps |= pdata->host_caps;

	host->quirks |= (SDHCI_QUIRK_32BIT_DMA_ADDR |
			 SDHCI_QUIRK_32BIT_DMA_SIZE);

	/* HSMMC on Samsung SoCs uses SDCLK as timeout clock */
	host->quirks |= SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK;

	/*
	 * If controller does not have internal clock divider,
	 * we can use overriding functions instead of default.
	 */
	if (pdata->clk_type) {
		sdhci_s3c_ops.set_clock = sdhci_cmu_set_clock;
		sdhci_s3c_ops.get_min_clock = sdhci_cmu_get_min_clock;
		sdhci_s3c_ops.get_max_clock = sdhci_cmu_get_max_clock;
	}

	/* It supports additional host capabilities if needed */
	if (pdata->host_caps)
		host->mmc->caps |= pdata->host_caps;

	ret = sdhci_add_host(host);
	if (ret) {
		dev_err(dev, "sdhci_add_host() failed\n");
		goto err_add_host;
	}

	/* The following two methods of card detection might call
	   sdhci_s3c_notify_change() immediately, so they can be called
	   only after sdhci_add_host(). Setup errors are ignored. */
	if (pdata->cd_type == S3C_SDHCI_CD_EXTERNAL && pdata->ext_cd_init)
		pdata->ext_cd_init(&sdhci_s3c_notify_change);
	if (pdata->cd_type == S3C_SDHCI_CD_GPIO &&
	    gpio_is_valid(pdata->ext_cd_gpio))
		sdhci_s3c_setup_card_detect_gpio(sc);

	return 0;

 err_add_host:
	release_resource(sc->ioarea);
	kfree(sc->ioarea);

 err_req_regs:
	for (ptr = 0; ptr < MAX_BUS_CLK; ptr++) {
		clk_disable(sc->clk_bus[ptr]);
		clk_put(sc->clk_bus[ptr]);
	}

 err_no_busclks:
	clk_disable(sc->clk_io);
	clk_put(sc->clk_io);

 err_io_clk:
	sdhci_free_host(host);

	return ret;
}

有點長，但可以看出大致流程還是sdhci-alloc-host -> sdhci-add-host。

主機控制器驅動添加完成後，如果platform_data的cd_type值爲EXTERNAL或者GPIO，就是調用相應函數進行檢測。

關於三星對cd_type的定義，可以在platform-samsung/include/plat/sdhci.h找到：

enum cd_types {
	S3C_SDHCI_CD_INTERNAL,	/* use mmc internal CD line */
	S3C_SDHCI_CD_EXTERNAL,	/* use external callback */
	S3C_SDHCI_CD_GPIO,	/* use external gpio pin for CD line */
	S3C_SDHCI_CD_NONE,	/* no CD line, use polling to detect card */
	S3C_SDHCI_CD_PERMANENT,	/* no CD line, card permanently wired to host */
};

幾種卡檢測模式沒有具體研究，但三星在定義platform_data變量的時候並沒有對cd_type成員賦值，也就是說隨機，但在platform_samsung/dev-hsmmc.c中設置平臺數據時有隱性表示：

void s3c_sdhci0_set_platdata(struct s3c_sdhci_platdata *pd)
{
	struct s3c_sdhci_platdata *set = &s3c_hsmmc0_def_platdata;

	set->cd_type = pd->cd_type;
	set->ext_cd_init = pd->ext_cd_init;
	set->ext_cd_cleanup = pd->ext_cd_cleanup;
	set->ext_cd_gpio = pd->ext_cd_gpio;
	set->ext_cd_gpio_invert = pd->ext_cd_gpio_invert;

	if (pd->max_width)
		set->max_width = pd->max_width;
	if (pd->cfg_gpio)
		set->cfg_gpio = pd->cfg_gpio;
	if (pd->cfg_card)
		set->cfg_card = pd->cfg_card;
	if (pd->host_caps)
		set->host_caps |= pd->host_caps;
	if (pd->clk_type)
		set->clk_type = pd->clk_type;
}

可以看到，三星官方驅動認爲cd_type必須給出，而max_width是可選變量。因此cd_type最好是定義下，否則可能導致驅動正常加載，但識別不到卡。

可以看到官方的說明，關於後兩種cd_type，可能是程序一直在執行檢測，我沒有仔細研究，但測試了兩個類型，全部可以識別到卡。

平臺驅動的註冊流程大致就這麼多，只是做了框架性分析，因此內容並不多，下面看下平臺設備是怎麼註冊的。

平臺設備定義mach-s3c64xx/mach-mini6410.c:

static struct platform_device *mini6410_devices[] __initdata = {
	&mini6410_device_eth,
	&s3c_device_hsmmc0,
	&s3c_device_hsmmc1,
	&s3c_device_ohci,
	&s3c_device_nand,
	&s3c_device_fb,
	&mini6410_lcd_powerdev,
	&s3c_device_adc,
	&s3c_device_ts,
};

mmc0設備plat-samsung/dev-hsmmc.c:

struct platform_device s3c_device_hsmmc0 = {
	.name		= "s3c-sdhci",
	.id		= 0,
	.num_resources	= ARRAY_SIZE(s3c_hsmmc_resource),
	.resource	= s3c_hsmmc_resource,
	.dev		= {
		.dma_mask		= &s3c_device_hsmmc_dmamask,
		.coherent_dma_mask	= 0xffffffffUL,
		.platform_data		= &s3c_hsmmc0_def_platdata,
	},
};

資源定義：

#define S3C_SZ_HSMMC	(0x1000)

static struct resource s3c_hsmmc_resource[] = {
	[0] = {
		.start = S3C_PA_HSMMC0,
		.end   = S3C_PA_HSMMC0 + S3C_SZ_HSMMC - 1,
		.flags = IORESOURCE_MEM,
	},
	[1] = {
		.start = IRQ_HSMMC0,
		.end   = IRQ_HSMMC0,
		.flags = IORESOURCE_IRQ,
	}
};

platform_data定義：

struct s3c_sdhci_platdata s3c_hsmmc0_def_platdata = {
	.max_width	= 4,
	.host_caps	= (MMC_CAP_4_BIT_DATA |
			   MMC_CAP_MMC_HIGHSPEED | MMC_CAP_SD_HIGHSPEED),
	.clk_type	= S3C_SDHCI_CLK_DIV_INTERNAL,
};

設備數據在平臺初始化的過程中會做修改，文件mach-s3c64xx/mach-mini6410.c：

static void __init mini6410_machine_init(void)
{
	// mmc platdata - remme
	s3c_sdhci0_set_platdata(&mini6410_hsmmc0_pdata);

	u32 cs1;
	struct mini6410_features_t features = { 0 };

	printk(KERN_INFO "MINI6410: Option string mini6410=%s\n",
			mini6410_features_str);

	/* Parse the feature string */
	mini6410_parse_features(&features, mini6410_features_str);

	mini6410_lcd_pdata.win[0] = &mini6410_fb_win[features.lcd_index];

	printk(KERN_INFO "MINI6410: selected LCD display is %dx%d\n",
		mini6410_lcd_pdata.win[0]->win_mode.xres,
		mini6410_lcd_pdata.win[0]->win_mode.yres);

	s3c_nand_set_platdata(&mini6410_nand_info);
	s3c_fb_set_platdata(&mini6410_lcd_pdata);
	s3c24xx_ts_set_platdata(&s3c_ts_platform);

	/* configure nCS1 width to 16 bits */

	cs1 = __raw_readl(S3C64XX_SROM_BW) &
		~(S3C64XX_SROM_BW__CS_MASK << S3C64XX_SROM_BW__NCS1__SHIFT);
	cs1 |= ((1 << S3C64XX_SROM_BW__DATAWIDTH__SHIFT) |
		(1 << S3C64XX_SROM_BW__WAITENABLE__SHIFT) |
		(1 << S3C64XX_SROM_BW__BYTEENABLE__SHIFT)) <<
			S3C64XX_SROM_BW__NCS1__SHIFT;
	__raw_writel(cs1, S3C64XX_SROM_BW);

	/* set timing for nCS1 suitable for ethernet chip */

	__raw_writel((0 << S3C64XX_SROM_BCX__PMC__SHIFT) |
		(6 << S3C64XX_SROM_BCX__TACP__SHIFT) |
		(4 << S3C64XX_SROM_BCX__TCAH__SHIFT) |
		(1 << S3C64XX_SROM_BCX__TCOH__SHIFT) |
		(13 << S3C64XX_SROM_BCX__TACC__SHIFT) |
		(4 << S3C64XX_SROM_BCX__TCOS__SHIFT) |
		(0 << S3C64XX_SROM_BCX__TACS__SHIFT), S3C64XX_SROM_BC1);

	gpio_request(S3C64XX_GPF(15), "LCD power");
	gpio_request(S3C64XX_GPE(0), "LCD power");

	platform_add_devices(mini6410_devices, ARRAY_SIZE(mini6410_devices));
}

函數第一行有一句設置平臺數據，平臺數據定義如下：

static struct s3c_sdhci_platdata mini6410_hsmmc0_pdata = {
	.max_width      = 4,
	.cd_type        = S3C_SDHCI_CD_NONE,
};

由於該部分數據可能因爲板子設計不一樣而不相同，因此，三星並沒有把該部分數據納入到平臺設備文件中，需要沒個平臺自己配置好參數，並調用設置平臺數據函數進行設置。

這也是爲什麼新下載的內核配置好SD/MMC驅動後編譯運行，SD卡驅動和平臺設備均正常加載，但缺識別不到SD卡。就是因爲默認情況下cd_type類型是不確定的，因此，卡無法被檢測到，應該根據平臺設置爲相應的模式sd驅動程序纔可以檢測到。

至此，大致的流程全部分析完畢，在這個過程中我自己遇到的問題和需要注意的問題也用紅色加粗很明確的標識了出來。

爲了解決無法識別到SD卡的問題，下載編譯了2.6.38、3.0.8、3.4的內核，並一一和官方比較，由於驅動加載都正常，導致整個查找過程可謂大海撈針，最終確定爲平臺啓動文件中需要配置mmc設備數據。前後花了差不多2天時間，就等着搞定這個驅動了，下一步應該就可以將自己編譯的安卓4.3啓動了。等4.3成功啓動了，下次再好好做個總結。