高通SDHCI(SDC)接口，SD卡初始化，检测等

来源：互联网发布：九十年代的事件知乎编辑：程序博客网时间：2024/05/16 01:51

    sdhc_2: sdhci@7864900 {        compatible = "qcom,sdhci-msm";        reg = <0x7864900 0x11c>, <0x7864000 0x800>;        reg-names = "hc_mem", "core_mem";        interrupts = <0 125 0>, <0 221 0>;        interrupt-names = "hc_irq", "pwr_irq";        qcom,bus-width = <4>;        qcom,large-address-bus;        qcom,cpu-dma-latency-us = <701>;        qcom,msm-bus,name = "sdhc2";        qcom,msm-bus,num-cases = <8>;        qcom,msm-bus,num-paths = <1>;        qcom,msm-bus,vectors-KBps = <81 512 0 0>, /* No vote */            <81 512 1046 3200>,    /* 400 KB/s*/            <81 512 52286 160000>, /* 20 MB/s */            <81 512 65360 200000>, /* 25 MB/s */            <81 512 130718 400000>, /* 50 MB/s */            <81 512 261438 800000>, /* 100 MB/s */            <81 512 261438 800000>, /* 200 MB/s */            <81 512 1338562 4096000>; /* Max. bandwidth */        qcom,bus-bw-vectors-bps = <0 400000 20000000 25000000 50000000                        100000000 200000000 4294967295>;        clocks = <&clock_gcc clk_gcc_sdcc2_ahb_clk>,             <&clock_gcc clk_gcc_sdcc2_apps_clk>;        clock-names = "iface_clk", "core_clk";        qcom,clk-rates = <400000 25000000 50000000 100000000 200000000>;        status = "disabled";    };

&sdhc_2 {    vdd-supply = <&pm8950_l11>;    qcom,vdd-voltage-level = <2950000 2950000>;    qcom,vdd-current-level = <15000 800000>;    vdd-io-supply = <&pm8950_l12>;    qcom,vdd-io-voltage-level = <1800000 2950000>;    qcom,vdd-io-current-level = <200 22000>;    pinctrl-names = "active", "sleep";    pinctrl-0 = <&sdc2_clk_on &sdc2_cmd_on &sdc2_data_on &sdc2_cd_on>;    pinctrl-1 = <&sdc2_clk_off &sdc2_cmd_off &sdc2_data_off &sdc2_cd_off>;    #address-cells = <0>;    interrupt-parent = <&sdhc_2>;    interrupts = <0 1 2>;    #interrupt-cells = <1>;    interrupt-map-mask = <0xffffffff>;    interrupt-map = <0 &intc 0 125 0            1 &intc 0 221 0            2 &msm_gpio 52 0>;    interrupt-names = "hc_irq", "pwr_irq", "status_irq";    cd-gpios = <&msm_gpio 52 0x1>;    status = "ok";};

sdhci_msm_probe() [sdhci-msm.c文件]除了读取上面的of内容初始化gpio,reg等之外，比较重要的有以下几个
1. 调用mmc_gpio_request_cd()设置sd卡检测中断，中断回调函数是mmc_rescan()。检测的地方还有一处就是mmc_start_host->mmc_detect_change -> mmc_rescan ->mmc_rescan_try_freq()
2. sdhci_alloc_host()->创建mmc_host赋值，并初始化一个workqueue以便mmc_rescan函数调用。然后调用mmc_add_host(mmc)初始化驱动文件等。

[http://blog.csdn.net/kickxxx/article/details/51130888 # emmc初始化过程]

驱动初始化之后，vold就可以收到uevent消息，并开始mount。中间过程省略，直接到PublicVolume::doMount()函数，这里check_filesystem_format会读/dev/block/vold/public:179,65设备节点检查文件系统类型。我的sd卡是fat类型的，最后vfat::Mount()调到kernel/fs/fat下面对应的mount文件输出如下log。

<6>[73637.264432]  [7:           vold:  462] FAT-fs (mmcblk1p1[179:65]): trying to mount...<6>[73637.283354]  [3:           vold:  462] FAT-fs (mmcblk1p1[179:65]): mounted successfully!<7>[73637.283581]  [3:           vold:  462] SELinux: initialized (dev mmcblk1p1, type vfat), uses genfs_contexts

mount成功后，vold就把vfat文件系统mount到/mnt/media_rw/XXX这个文件夹下面了。

随后vold会再execl(“/system/bin/sdcard”,xxx)，居然运行sdcard再去用sdcardfs文件系统类型(这个在kernel/fs/sdcard里，是三星做的，可以比fuse减少io交互，提高读写性能)，再mount一下。内核的sdcardfs文件系统的内容就不在这里说了。

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