首先，先修復上一個篇文章遺留下來的問題，即uboot起來後顯示內容容量只有512M的問題，後來查看了4412的晶片手冊，發現是有暫存器沒有設定正確，所以才導致記憶體容量識別有問題，按照下面的修改，我們的uboot就能識別到1G的記憶體容量了！

diff --git a/arch/arm/mach-exynos/exynos4_setup.h b/arch/arm/mach-exynos/exynos4_setup.h
index 9e252ad..b3477e7 100644
--- a/arch/arm/mach-exynos/exynos4_setup.h
+++ b/arch/arm/mach-exynos/exynos4_setup.h
@@ -385
 
,7 +385,7 @@ struct mem_timings {
 #define ADD_LAT_PALL           (1 << 6)
 #define MEM_TYPE_DDR3          (0x6 << 8)
 #define MEM_WIDTH_32           (0x2 << 12)
-#define NUM_CHIP_2             (1 << 16)
+#define NUM_CHIP_2             (0 << 16)
 #define BL_8                   (0x3 << 20)
 

 #define MEMCONTROL_VAL         (CLK_STOP_DISABLE | DPWRDN_DISABLE\
                                | DPWRDN_TYPE | TP_DISABLE | DSREF_DIABLE\
@@ -394,16 +394,16 @@ struct mem_timings { 
 #define CHIP_BANK_8            (0x3 << 0)
-#define CHIP_ROW_14            (0x2 << 4)
+#define CHIP_ROW_14            (0x3 << 4)
 

 #define CHIP_COL_10            (0x3 << 8)
 #define CHIP_MAP_INTERLEAVED   (1 << 12)
-#define CHIP_MASK              (0xe0 << 16)
+#define CHIP_MASK              (0xC0 << 16)
 #ifdef CONFIG_MIU_LINEAR
 #define CHIP0_BASE             (0x40 << 24)
 #define CHIP1_BASE             (0x60 << 24)
 #else
-#define CHIP0_BASE             (0x20 << 24)
-#define CHIP1_BASE             (0x40 << 24)
+#define CHIP0_BASE             (0x40 << 24)
+#define CHIP1_BASE             (0x80 << 24)
 #endif
 #define MEMCONFIG0_VAL         (CHIP_BANK_8 | CHIP_ROW_14 | CHIP_COL_10\
                                | CHIP_MAP_INTERLEAVED | CHIP_MASK | CHIP0_BASE)

上面就是簡單的將暫存器的值修改一下，設定開發板的最大記憶體定址範圍。這樣就OK了。重新編譯燒寫啟動後，輸出如下：

U-Boot 2016.11-gbf241c8 (Mar 04 2017 - 06:46:50 +0800) for TINY4412

CPU:   Exynos4412 @ 1.4 GHz
Model: Insignal Tiny4412 evaluation board based on Exynos4412
Board: Insignal Tiny4412 evaluation board based on Exynos4412
DRAM:  1 GiB
WARNING: Caches not enabled
MMC:   DWMMC56: Can't get the dev index
exynos_dwmci_process_node: failed to decode dev 0
SAMSUNG SDHCI: 0
sdhci_transfer_data: Error detected in status(0x208002)!
sdhci_transfer_data: Error detected in status(0x208002)!
sdhci_transfer_data: Error detected in status(0x208000)!
*** Warning - read failed, using default environment

Hit any key to stop autoboot:  0 
sdhci_transfer_data: Error detected in status(0x208002)!
sdhci_transfer_data: Error detected in status(0x208002)!
sdhci_transfer_data: Error detected in status(0x208000)!
SD/MMC found on device 0
 ** ext4fs_devread read error - block
Failed to mount ext2 filesystem...
** Unrecognized filesystem type **
 ** ext4fs_devread read error - block
Failed to mount ext2 filesystem...
** Unrecognized filesystem type **
 ** ext4fs_devread read error - block
Failed to mount ext2 filesystem...
** Unrecognized filesystem type **
Wrong Image Format for bootm command
ERROR: can't get kernel image!

上面有兩處需要修復的：
第一點是：
DWMMC56: Can’t get the dev index
exynos_dwmci_process_node: failed to decode dev 0

第二點是：
sdhci_transfer_data: Error detected in status(0x208002)!
sdhci_transfer_data: Error detected in status(0x208002)!
sdhci_transfer_data: Error detected in status(0x208000)!

首先解決第一點，看輸出是因為沒有給EMMC新增相應的節點，導致在解析的時候出問題了，檢視Tiny4412的裝置樹檔案，會發現確實沒有給EMMC新增裝置描述，我們新增下面的資訊就可以解決找不到節點的問題了。

diff --git a/arch/arm/dts/exynos4210-tiny4412.dts b/arch/arm/dts/exynos4210-tiny4412.dts
index a4fe14f..77934e5 100644
--- a/arch/arm/dts/exynos4210-tiny4412.dts
+++ b/arch/arm/dts/exynos4210-tiny4412.dts
@@ -49,4 +49,14 @@
        [email protected] {
                status = "disabled";
        };
+
+       [email protected] {
+               samsung,bus-width = <8>;
+               samsung,timing = <2 1 0>;
+               samsung,removable = <0>;
+               fifoth_val = <0x203f0040>;
+               bus_hz = <400000000>;
+               div = <0x3>;
+               index = <4>;
+       };
 };

diff --git a/arch/arm/mach-exynos/clock.c b/arch/arm/mach-exynos/clock.c
index 3d31f9d..a8fc72a 100644
--- a/arch/arm/mach-exynos/clock.c
+++ b/arch/arm/mach-exynos/clock.c
@@ -1688,8 +1688,8 @@ unsigned long get_mmc_clk(int dev_index)
 void set_mmc_clk(int dev_index, unsigned int div)
 {
        /* If want to set correct value, it needs to substract one from div.*/
-       if (div > 0)
-               div -= 1;
+//     if (div > 0)
+//             div -= 1;

        if (cpu_is_exynos5()) {
                if (proid_is_exynos5420() || proid_is_exynos5422())

然後上面顯示的error都沒有顯示了，而且執行saveenv，顯示done，執行mmc read/write顯示的都是done，但是驗證的時候發現都沒有效果，我是通過執行mmc read 0x43E00000 0x800 0x100，意思是將mmc裝置中第2048個block開始，讀取256個block到記憶體0x43E00000，即u-boot執行的首地址處，然後在執行go 0x43E00000，如果mmc裝置正常的話，通過上面的操作，0x43E00000位置的內容應該要被覆蓋，那麼go 0x43E00000操作後，開發板應該是宕機才對的，但是開發板是重新執行了uboot的初始化過程，因此看起來像是mmc裝置還是沒有初始化成功啊，起碼mmc write/read都不能正常執行。

所以如果有哪位朋友也遇到過這種情況，還請和大家分享一下啊，謝謝！