平台简介

开发板：tiny4412ADK + S700 + 4GB Flash

要移植的内核版本：Linux-4.4.0 （支持device tree）

u-boot版本：友善之臂自带的 U-Boot 2010.12 （为支持uImage启动，做了少许改动）

busybox版本：busybox 1.25

eMMC：KLMxGxFE3x-x00x

交叉编译工具链： arm-none-linux-gnueabi-gcc

      （gcc version 4.8.3 20140320 (prerelease) (Sourcery CodeBench Lite 2014.05-29)）

概述

    eMMC驱动在内核中也已经支持好了，代码在：drivers/mmc/host/dw_mmc-exynos.c，我们要做的就是修改设备树配置文件。

移植

一、原理图

eMMC这部分电路都在核心板上：

 从上图看到，tiny4412上exynos4412与eMMC传输数据的总线宽度是8位，使用的控制器是Mobile Storage Host，占用了SDMMC0和SDMMC1的资源，即SDMMC0和SDMMC1的引脚被复用为SD_4功能。具体信息请参考Exynos4412的用户手册的 第23节Mobile Storage Host：

 二、修改设备树

这部分我参考了arch/arm/boot/dts/exynos4412-trats2.dts,对arch/arm/boot/dts/exynos4412-tiny4412.dts做了如下修改：

diff --git a/arch/arm/boot/dts/exynos4412-tiny4412.dts b/arch/arm/boot/dts/exynos4412-tiny4412.dts

index bd823eb..585cab7 100644

--- a/arch/arm/boot/dts/exynos4412-tiny4412.dts

+++ b/arch/arm/boot/dts/exynos4412-tiny4412.dts

@@ -106,6 +106,23 @@

     status = "okay";

 };

+&mshc_0 {

+    num-slots = <1>;

+    broken-cd;

+    non-removable;

+    card-detect-delay = <200>;

+    vmmc-supply = <&mmc_reg>;

+    clock-frequency = <400000000>;

+    samsung,dw-mshc-ciu-div = <0>;

+    samsung,dw-mshc-sdr-timing = <2 3>;

+    samsung,dw-mshc-ddr-timing = <1 2>;

+    pinctrl-0 = <&sd4_clk &sd4_cmd &sd4_bus4 &sd4_bus8>;

+    pinctrl-names = "default";

+    status = "okay";

+    bus-width = <8>;

+    cap-mmc-highspeed;

+};

+

 &serial_0 {

     status = "okay";

 };

实际测试时发现不设置vmmc-supply也可以正常工作，上面的这些参数我直接从arch/arm/boot/dts/exynos4412-trats2.dts拷贝过来的，没有做任何改动，其中mshc0是在arch/arm/boot/dts/exynos4x12.dtsi定义的：

mshc_0: mmc@12550000 {

    compatible = "samsung,exynos4412-dw-mshc";

    reg = <0x12550000 0x1000>;

    interrupts = <0 77 0>;

    #address-cells = <1>;

    #size-cells = <0>;

    fifo-depth = <0x80>;

    clocks = <&clock CLK_SDMMC4>, <&clock CLK_SCLK_MMC4>;

    clock-names = "biu", "ciu";

    status = "disabled";

};

三、测试

下面是启动log：

   1: [    2.286502] dwmmc_exynos 12550000.mmc: IDMAC supports 32-bit address mode.

   2: [    2.286613] dwmmc_exynos 12550000.mmc: Using internal DMA controller.

   3: [    2.289979] dwmmc_exynos 12550000.mmc: Version ID is 240a

   4: [    2.295396] dwmmc_exynos 12550000.mmc: DW MMC controller at irq 89,32 bit host data width,128 deep fifo

   5: [    2.304812] dwmmc_exynos 12550000.mmc: No vqmmc regulator found

   6: [    2.340643] dwmmc_exynos 12550000.mmc: 1 slots initialized

   7: [    2.341935] usbcore: registered new interface driver usbhid

   8: [    2.341991] usbhid: USB HID core driver

   9: [    2.344435] NET: Registered protocol family 10

  10: [    2.345015] sit: IPv6 over IPv4 tunneling driver

  11: [    2.345497] NET: Registered protocol family 17

  12: [    2.346734] NET: Registered protocol family 15

  13: [    2.351355] Registering SWP/SWPB emulation handler

  14: [    2.357490] hctosys: unable to open rtc device (rtc0)

  15: [    2.365652] usb 2-2: new high-speed USB device number 2 using exynos-ehci

  16: [    2.380409] ALSA device list:

  17: [    2.380451]   No soundcards found.

  18: [    2.381460] RAMDISK: gzip image found at block 0

  19: [    2.383346] mmc1: MAN_BKOPS_EN bit is not set

  20: [    2.384095] mmc_host mmc1: Bus speed (slot 0) = 50000000Hz (slot req 52000000Hz, actual 50000000HZ div = 0)

  21: [    2.392918] mmc_host mmc1: Bus speed (slot 0) = 100000000Hz (slot req 52000000Hz, actual 50000000HZ div = 1)

  22: [    2.402558] mmc1: new DDR MMC card at address 0001

  23: [    2.407922] mmcblk0: mmc1:0001 M4G1YC 3.64 GiB 

  24: [    2.412049] mmcblk0boot0: mmc1:0001 M4G1YC partition 1 2.00 MiB

  25: [    2.417930] mmcblk0boot1: mmc1:0001 M4G1YC partition 2 2.00 MiB

  26: [    2.424030] mmcblk0rpmb: mmc1:0001 M4G1YC partition 3 128 KiB

  27: [    2.430169]  mmcblk0: p1 p2 p3 p4

查看一下：

   1: [root@tiny4412 ]# ls /dev/mmcblk* -l

   2: brw-rw----    1 0        0         179,   0 Jan  1 00:00 /dev/mmcblk0

   3: brw-rw----    1 0        0         179,  16 Jan  1 00:00 /dev/mmcblk0boot0

   4: brw-rw----    1 0        0         179,  32 Jan  1 00:00 /dev/mmcblk0boot1

   5: brw-rw----    1 0        0         179,   1 Jan  1 00:00 /dev/mmcblk0p1

   6: brw-rw----    1 0        0         179,   2 Jan  1 00:00 /dev/mmcblk0p2

   7: brw-rw----    1 0        0         179,   3 Jan  1 00:00 /dev/mmcblk0p3

   8: brw-rw----    1 0        0         179,   4 Jan  1 00:00 /dev/mmcblk0p4

   9: brw-rw----    1 0        0         179,  48 Jan  1 00:00 /dev/mmcblk0rpmb

  10: brw-rw----    1 0        0         179,  64 Jan  1 00:00 /dev/mmcblk1

  11: brw-rw----    1 0        0         179,  65 Jan  1 00:00 /dev/mmcblk1p1

其中mmcblk1是我们的sdcard，mmcblk0是核心板上的eMMC。 我在eMMC中烧写的是Android系统，可以看到Android系统有7个分区，下面我们挂载一个分区看看：

   1: [root@tiny4412 ]# mount -t ext4 /dev/mmcblk0p2 /mnt

   2: [  287.710063] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null)

   3: [root@tiny4412 ]# ls /mnt/

   4: addon.d     build.prop  fonts       lost+found  tts         xbin

   5: app         busybox     framework   media       usr

   6: bin         etc         lib         priv-app    vendor

代码我已经上传到了github上：

git clone https://github.com/pengdonglin137/linux-4.4_tiny4412.git -b port_to_tiny4412