基于tiny4412的Linux内核移植 -- SD卡驱动移植（五）

作者信息

作者: 彭东林

邮箱：pengdonglin137@163.com

QQ：405728433

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

SD卡：Kingston SDHC 4GB

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

    移植SD卡比较简单，但是刚开始的时候也出现了不少问题，关键是对设备树的修改、对regulator的理解以及sdcard检测过程。

移植

    下面是tiny4412关于sd卡部分的原理图：

底板：

核心板：

从原理图可以看出，tiny4412用的MMC控制器是SDMMC2。一共用到了7个引脚（CLK、CMD、CDn、DATA0-DATA3），其中CDn的意思是当插入SD卡时，这个引脚的电平会被拉低（可以轮询这个引脚的电平转态或者通过设置这个引脚产生中断来检测sdcard状态）。在之前的移植中我们将sdhc2给disabled了：

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

&sdhci_2 {

    bus-width = <4>;

    pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>;

    pinctrl-names = "default";

    status = "disabled";

};

其中princtrl-0后的作用是设置用到的GPIO的复用功能（一旦复用为sdcard控制器的专用引脚后，就不能作为普通的gpio使用了），这几个标号是在arch/arm/boot/dts/exynos4x12-pinctrl.dtsi中定义的：

sd2_clk: sd2-clk {
    samsung,pins = "gpk2-0";
    samsung,pin-function = <2>;
    samsung,pin-pud = <0>;
    samsung,pin-drv = <3>;
};

sd2_cmd: sd2-cmd {
    samsung,pins = "gpk2-1";
    samsung,pin-function = <2>;
    samsung,pin-pud = <0>;
    samsung,pin-drv = <3>;
};

sd2_cd: sd2-cd {
    samsung,pins = "gpk2-2";
    samsung,pin-function = <2>;
    samsung,pin-pud = <3>;
    samsung,pin-drv = <3>;
};

sd2_bus4: sd2-bus-width4 {
    samsung,pins = "gpk2-3", "gpk2-4", "gpk2-5", "gpk2-6";
    samsung,pin-function = <2>;
    samsung,pin-pud = <3>;
    samsung,pin-drv = <3>;
};

这样只是设置了这几个GPIO的复用功能,并不用在驱动程序中申请这几个GPIO资源,因为这几个引脚已经不是作为普通的GPIO使用了。

如果直接将sdhc2使能的话：

--- a/arch/arm/boot/dts/exynos4412-tiny4412.dts
+++ b/arch/arm/boot/dts/exynos4412-tiny4412.dts
@@ -86,7 +86,7 @@
        bus-width = <4>;
        pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>;
        pinctrl-names = "default";
-       status = "disabled";
+       status = "okay";
 };

 &serial_0 {

内核在启动时会崩溃，信息如下：

[    2.228406] sdhci: Secure Digital Host Controller Interface driver
[    2.233751] sdhci: Copyright(c) Pierre Ossman
[    2.238350] s3c-sdhci 12530000.sdhci: clock source 2: mmc_busclk.2 (100000000 Hz)
[    2.245838] s3c-sdhci 12530000.sdhci: No vmmc regulator found
[    2.251358] s3c-sdhci 12530000.sdhci: No vqmmc regulator found
[    2.257480] ------------[ cut here ]------------
[    2.261686] kernel BUG at drivers/mmc/host/sdhci.c:1304!
[    2.266981] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
[    2.272796] Modules linked in:
[    2.275836] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.4.0-gbd7378b-dirty #33
[    2.283038] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[    2.289115] task: ef078000 ti: ef080000 task.ti: ef080000
[    2.294500] PC is at sdhci_do_set_ios+0x564/0x5e0
[    2.299189] LR is at arm_heavy_mb+0x1c/0x38
[    2.303351] pc : [<c0406f38>]    lr : [<c00198b0>]    psr: 80000093
[    2.303351] sp : ef081cc8  ip : 00000200  fp : 00000001
[    2.314807] r10: 00000003  r9 : ef30e800  r8 : 60000013
[    2.320015] r7 : ef30e800  r6 : ef30ec98  r5 : ef30ea34  r4 : ef30eb80
[    2.326525] r3 : 00000001  r2 : 75004180  r1 : 00000000  r0 : ef30eb80
[    2.333036] Flags: Nzcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
[    2.340240] Control: 10c5387d  Table: 4000404a  DAC: 00000051
[    2.345969] Process swapper/0 (pid: 1, stack limit = 0xef080210)
[    2.351958] Stack: (0xef081cc8 to 0xef082000)
[    2.356300] 1cc0:                   00000000 ef30eb80 00000043 c02d30e8 c02d30e8 00000004
[    2.364460] 1ce0: c0058b5c ef080000 ef1a6ebc c0407168 ef1a6e10 ef1a6e80 c02d30e8 c02d3114
[    2.372619] 1d00: 00000004 c02d465c ef1a6e10 c0852100 c086ea10 c02d46b0 00000000 ef1a6e10
[    2.380778] 1d20: c0852100 c02d54fc eeca0fa0 c00f2934 00000188 eeca0fa0 ef078000 60000013
[    2.388937] 1d40: ef1a6e80 ef1a6e10 ef1a6e80 00000004 60000013 00000000 00000002 ef30ea80
[    2.397096] 1d60: 00000000 c02d56c8 00000000 ef30e800 ef30ea24 60000013 ef080000 c03eff80
[    2.405256] 1d80: eec0b7b8 00000000 ef078000 c0044ee8 00000100 00000200 eec0b6b4 ef30e800
[    2.413415] 1da0: ef30ed2c ef30eb80 ef30e800 00000000 00000200 00000000 ef30ed18 c03f2fd8
[    2.421574] 1dc0: ef30e800 c03f41ac 00000000 c0407ba4 ef264300 ef30eb80 00000808 ef30e800
[    2.429733] 1de0: ef7d3488 00000000 00000000 c03f3dd4 00000000 ef30eb80 00000004 ef1a6e10
[    2.437893] 1e00: ef1a6e00 ef30edec 00000001 ef264110 00000000 c0408be8 05f5e100 c087a810
[    2.446052] 1e20: ef17df50 c087a8a4 5f636d6d 63737562 332e6b6c ee9d9600 00000001 ef1a6e10
[    2.454211] 1e40: fffffffe fffffdfb c087a810 c087a810 00000000 c081683c c0816848 c02ce238
[    2.462370] 1e60: c02ce1e8 ef1a6e10 c08d942c c088e410 00000000 c02cc634 c087a810 ef1a6e44
[    2.470529] 1e80: c088e338 ef1a6e10 c087a810 ef1a6e44 c088e338 00000000 00000000 c02cc8d4
[    2.478688] 1ea0: 00000000 c087a810 c02cc848 c02ca7d4 ef003274 ef17b7c0 c087a810 eebf6f00
[    2.486848] 1ec0: c086ebc8 c02cbb48 c0755dc0 c087a810 c087a810 c0855520 ef267240 c089c000
[    2.495007] 1ee0: c08023cc c02cd0cc c087a7fc c0855520 c0855520 c00097a0 ef15eb00 c0598680
[    2.503166] 1f00: 00000025 0000c000 ef078000 60000013 efffca92 c05aba2c 000000c0 c003da88
[    2.511325] 1f20: 00000001 00000003 c0746c3c c07b1804 00000000 c088c6b8 00000006 00000006
[    2.519484] 1f40: c0858ec8 c0849e3c c084a108 00000006 c089c000 c089c000 c07e35b0 000000c0
[    2.527643] 1f60: c081683c c07e3dec 00000006 00000006 00000000 c07e35b0 ef078000 c0042518
[    2.535802] 1f80: 000000a2 00000000 c058e6c8 00000000 00000000 00000000 00000000 00000000
[    2.543962] 1fa0: 00000000 c058e6d0 00000000 c0010338 00000000 00000000 00000000 00000000
[    2.552121] 1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    2.560280] 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000 dffffefb f5fbff7f
[    2.568447] [<c0406f38>] (sdhci_do_set_ios) from [<c0407168>] (sdhci_runtime_resume_host+0x60/0x114)
[    2.577557] [<c0407168>] (sdhci_runtime_resume_host) from [<c02d3114>] (pm_generic_runtime_resume+0x2c/0x38)
[    2.587366] [<c02d3114>] (pm_generic_runtime_resume) from [<c02d465c>] (__rpm_callback+0x2c/0x60)
[    2.596216] [<c02d465c>] (__rpm_callback) from [<c02d46b0>] (rpm_callback+0x20/0x80)
[    2.603942] [<c02d46b0>] (rpm_callback) from [<c02d54fc>] (rpm_resume+0x3ac/0x52c)
[    2.611493] [<c02d54fc>] (rpm_resume) from [<c02d56c8>] (__pm_runtime_resume+0x4c/0x64)
[    2.619482] [<c02d56c8>] (__pm_runtime_resume) from [<c03eff80>] (__mmc_claim_host+0x190/0x19c)
[    2.628161] [<c03eff80>] (__mmc_claim_host) from [<c03f2fd8>] (mmc_start_host+0x38/0x98)
[    2.636232] [<c03f2fd8>] (mmc_start_host) from [<c03f41ac>] (mmc_add_host+0x58/0x7c)
[    2.643957] [<c03f41ac>] (mmc_add_host) from [<c0407ba4>] (sdhci_add_host+0x988/0xe80)
[    2.651855] [<c0407ba4>] (sdhci_add_host) from [<c0408be8>] (sdhci_s3c_probe+0x4a8/0x548)
[    2.660016] [<c0408be8>] (sdhci_s3c_probe) from [<c02ce238>] (platform_drv_probe+0x50/0xac)
[    2.668348] [<c02ce238>] (platform_drv_probe) from [<c02cc634>] (driver_probe_device+0x240/0x454)
[    2.677200] [<c02cc634>] (driver_probe_device) from [<c02cc8d4>] (__driver_attach+0x8c/0x90)
[    2.685626] [<c02cc8d4>] (__driver_attach) from [<c02ca7d4>] (bus_for_each_dev+0x60/0x94)
[    2.693780] [<c02ca7d4>] (bus_for_each_dev) from [<c02cbb48>] (bus_add_driver+0x1b8/0x26c)
[    2.702025] [<c02cbb48>] (bus_add_driver) from [<c02cd0cc>] (driver_register+0x78/0xf8)
[    2.710012] [<c02cd0cc>] (driver_register) from [<c00097a0>] (do_one_initcall+0xbc/0x1f4)
[    2.718176] [<c00097a0>] (do_one_initcall) from [<c07e3dec>] (kernel_init_freeable+0x158/0x1f8)
[    2.726855] [<c07e3dec>] (kernel_init_freeable) from [<c058e6d0>] (kernel_init+0x8/0xf0)
[    2.734927] [<c058e6d0>] (kernel_init) from [<c0010338>] (ret_from_fork+0x14/0x3c)
[    2.742474] Code: e3510000 05991010 ebf24b35 eaffff77 (e7f001f2)
[    2.748557] ---[ end trace 6068c23e2cfdffe9 ]---
[    2.753149] note: swapper/0[1] exited with preempt_count 1
[    2.758738] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[    2.758738]
[    2.767732] CPU1: stopping
[    2.770423] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G      D         4.4.0-gbd7378b-dirty #33
[    2.778840] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[    2.784927] [<c0016fc0>] (unwind_backtrace) from [<c0013ab8>] (show_stack+0x10/0x14)
[    2.792652] [<c0013ab8>] (show_stack) from [<c01fa9d8>] (dump_stack+0x80/0xc0)
[    2.799851] [<c01fa9d8>] (dump_stack) from [<c0016030>] (handle_IPI+0x1ac/0x1c0)
[    2.807227] [<c0016030>] (handle_IPI) from [<c00094d0>] (gic_handle_irq+0x90/0x94)
[    2.814778] [<c00094d0>] (gic_handle_irq) from [<c0014594>] (__irq_svc+0x54/0x90)
[    2.822240] Exception stack(0xef0aff88 to 0xef0affd0)
[    2.827277] ff80:                   00000001 00000000 ef0affe0 c001c860 c05977c8 00000000
[    2.835437] ffa0: 00000000 c084e3c0 c08524b4 c084b2e4 ef0ae000 c08524bc 00000001 ef0affd8
[    2.843594] ffc0: c0010da8 c0010dac 60000013 ffffffff
[    2.848631] [<c0014594>] (__irq_svc) from [<c0010dac>] (arch_cpu_idle+0x38/0x3c)
[    2.856015] [<c0010dac>] (arch_cpu_idle) from [<c0059018>] (cpu_startup_entry+0x1b0/0x26c)
[    2.864256] [<c0059018>] (cpu_startup_entry) from [<4000956c>] (0x4000956c)
[    2.871196] CPU3: stopping
[    2.873888] CPU: 3 PID: 0 Comm: swapper/3 Tainted: G      D         4.4.0-gbd7378b-dirty #33
[    2.882305] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[    2.888389] [<c0016fc0>] (unwind_backtrace) from [<c0013ab8>] (show_stack+0x10/0x14)
[    2.896113] [<c0013ab8>] (show_stack) from [<c01fa9d8>] (dump_stack+0x80/0xc0)
[    2.903315] [<c01fa9d8>] (dump_stack) from [<c0016030>] (handle_IPI+0x1ac/0x1c0)
[    2.910692] [<c0016030>] (handle_IPI) from [<c00094d0>] (gic_handle_irq+0x90/0x94)
[    2.918243] [<c00094d0>] (gic_handle_irq) from [<c0014594>] (__irq_svc+0x54/0x90)
[    2.925706] Exception stack(0xef0b3f88 to 0xef0b3fd0)
[    2.930743] 3f80:                   00000001 00000000 ef0b3fe0 c001c860 c05977c8 00000000
[    2.938902] 3fa0: 00000000 c084e3c0 c08524b4 c084b2e4 ef0b2000 c08524bc 00000001 ef0b3fd8
[    2.947060] 3fc0: c0010da8 c0010dac 60000013 ffffffff
[    2.952096] [<c0014594>] (__irq_svc) from [<c0010dac>] (arch_cpu_idle+0x38/0x3c)
[    2.959476] [<c0010dac>] (arch_cpu_idle) from [<c0059018>] (cpu_startup_entry+0x1b0/0x26c)
[    2.967720] [<c0059018>] (cpu_startup_entry) from [<4000956c>] (0x4000956c)
[    2.974661] CPU2: stopping
[    2.977354] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D         4.4.0-gbd7378b-dirty #33
[    2.985771] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[    2.991854] [<c0016fc0>] (unwind_backtrace) from [<c0013ab8>] (show_stack+0x10/0x14)
[    2.999578] [<c0013ab8>] (show_stack) from [<c01fa9d8>] (dump_stack+0x80/0xc0)
[    3.006781] [<c01fa9d8>] (dump_stack) from [<c0016030>] (handle_IPI+0x1ac/0x1c0)
[    3.014158] [<c0016030>] (handle_IPI) from [<c00094d0>] (gic_handle_irq+0x90/0x94)
[    3.021709] [<c00094d0>] (gic_handle_irq) from [<c0014594>] (__irq_svc+0x54/0x90)
[    3.029171] Exception stack(0xef0b1f88 to 0xef0b1fd0)
[    3.034208] 1f80:                   00000001 00000000 ef0b1fe0 c001c860 c05977c8 00000000
[    3.042368] 1fa0: 00000000 c084e3c0 c08524b4 c084b2e4 ef0b0000 c08524bc 00000001 ef0b1fd8
[    3.050525] 1fc0: c0010da8 c0010dac 60000013 ffffffff
[    3.055562] [<c0014594>] (__irq_svc) from [<c0010dac>] (arch_cpu_idle+0x38/0x3c)
[    3.062942] [<c0010dac>] (arch_cpu_idle) from [<c0059018>] (cpu_startup_entry+0x1b0/0x26c)
[    3.071185] [<c0059018>] (cpu_startup_entry) from [<4000956c>] (0x4000956c)
[    3.078130] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[    3.078130]

在第4和第5行可以看到：

[    2.245838] s3c-sdhci 12530000.sdhci: No vmmc regulator found
[    2.251358] s3c-sdhci 12530000.sdhci: No vqmmc regulator found

再结合打印出的栈信息，可以确定就是由于没有为sdhc2设置vmmc或者vqmmc导致的，这两个是关于regulator的，但是从开发板的原理图上看到，sdcard这部分的供电完全是在设计原理图时就固定死了，根本不需要什么regulator，但是经过分析drivers/mmc/host/sdhci-s3c.c文件中host的注册过程，还必须设置regulator信息。通过对比其他平台的设备树文件（主要是：arch/arm/boot/dts/exynos4412-origen.dts和arch/arm/boot/dts/exynos4412-trats2.dts），我对tiny4412的设备树文件进行了如下修改：

diff --git a/arch/arm/boot/dts/exynos4412-tiny4412.dts b/arch/arm/boot/dts/exynos4412-tiny4412.dts
index 69a0d5d..b82e303 100644
--- a/arch/arm/boot/dts/exynos4412-tiny4412.dts
+++ b/arch/arm/boot/dts/exynos4412-tiny4412.dts
@@ -75,7 +75,21 @@
         compatible = "smsc,usb4640";
         reset-gpios = <&gpm2 4 GPIO_ACTIVE_LOW>;
         initial-mode = <USB4640_MODE_HUB>;
-    };
+    };
+
+    regulators {
+        compatible = "simple-bus";
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        mmc_reg: regulator@0{
+            compatible = "regulator-fixed";
+            reg = <0>;
+            regulator-name = "VMEM_VDD_2.8V";
+            regulator-min-microvolt = <2800000>;
+            regulator-max-microvolt = <2800000>;
+        };
+    };
 };

 &rtc {
@@ -86,7 +100,10 @@
     bus-width = <4>;
     pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>;
     pinctrl-names = "default";
-    status = "disabled";
+    vmmc-supply = <&mmc_reg>;
+    cd-gpios = <&gpk2 2 GPIO_ACTIVE_HIGH>;
+    cd-inverted;
+    status = "okay";
 };

 &serial_0 {

在参考文件arch/arm/boot/dts/exynos4412-origen.dts中的mmc_reg配置中：

regulators {
    compatible = "simple-bus";
    #address-cells = <1>;
    #size-cells = <0>;

    mmc_reg: regulator@0 {
        compatible = "regulator-fixed";
        reg = <0>;
        regulator-name = "VMEM_VDD_2.8V";
        regulator-min-microvolt = <2800000>;
        regulator-max-microvolt = <2800000>;
        gpio = <&gpx1 1 GPIO_ACTIVE_HIGH>;
        enable-active-high;
    };
};

    可以看到，origen平台还配置有gpio资源（应该是用于控制板子上的某个LDO芯片的开关，目的是给sdcard供电，在开始测试的时候发现，如果也给tiny4412配置上gpio的话，在插入sdcard会，这个gpio电平会被控制器拉高，当拔出sdcard后，这个gpio的电平会被拉低，证明了我的猜想。感觉tiny4412做的有点不好的是板子上没有PMIC，因此不利于学习电源管理，因为一般的手机或者平板产品上都是有PMIC的），但是我们的tiny4412并不需要，所以我把gpio属性删去了，这里的电压2800000不要乱动，尽管对于tiny4412没什么用，但是如果设置不当，在内核启动log中会打印错误信息。

    还要说明的一点是：

cd-gpios = <&gpk2 2 GPIO_ACTIVE_HIGH>;
cd-inverted;

cd-gpios用于设置sdcard插入拔出检测引脚，从原理图中可以看到tiny4412的sdcard检测引脚(Xmmc2CDn)使用的是GPIOK2_2，这样在注册sd卡控制器(drivers/mmc/host/sdhci-s3c.c[sdhci_s3c_probe->sdhci_add_host]、drivers/mmc/host/sdhci.c[sdhci_add_host->mmc_add_host]、drivers/mmc/core/host.c[mmc_add_host->mmc_start_host]、drivers/mmc/core/core.c[mmc_start_host -> mmc_gpiod_request_cd_irg]、drivers/mmc/core/slot-gpio.c[mmc_gpiod_request_cd_irq])的时候就会在这个引脚上申请一个中断资源（实际中发现触发类型是上下沿触发 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | IRQF_ONESHOT ），如果这里设置了用gpio中断检测sdcard状态的属性，就可以把

pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>; 

改为

pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_bus4>;

 即删除对sdcard检测引脚的功能复用的设置，即不需要sdcard控制器这个硬件（结合exynos4412的用户手册发现，也需要驱动程序的配合才行）来检测sdcard状态。此时的patch如下：

diff --git a/arch/arm/boot/dts/exynos4412-tiny4412.dts b/arch/arm/boot/dts/exynos4412-tiny4412.dts
index 69a0d5d..bd823eb 100644
--- a/arch/arm/boot/dts/exynos4412-tiny4412.dts
+++ b/arch/arm/boot/dts/exynos4412-tiny4412.dts
@@ -75,7 +75,21 @@
         compatible = "smsc,usb4640";
         reset-gpios = <&gpm2 4 GPIO_ACTIVE_LOW>;
         initial-mode = <USB4640_MODE_HUB>;
-    };
+    };
+
+    regulators {
+        compatible = "simple-bus";
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        mmc_reg: regulator@0{
+            compatible = "regulator-fixed";
+            reg = <0>;
+            regulator-name = "VMEM_VDD_2.8V";
+            regulator-min-microvolt = <2800000>;
+            regulator-max-microvolt = <2800000>;
+        };
+    };
 };

 &rtc {
@@ -84,9 +98,12 @@

 &sdhci_2 {
     bus-width = <4>;
-    pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>;
+    pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_bus4>;
     pinctrl-names = "default";
-    status = "disabled";
+    vmmc-supply = <&mmc_reg>;
+    cd-gpios = <&gpk2 2 GPIO_ACTIVE_HIGH>;
+    cd-inverted;
+    status = "okay";
 };

 &serial_0 {

在测试时发现，如果使用sdcard控制器内部检测sdcard状态，那么在发生sdcard插拔动作时，Linux系统并不能识别到，不知道是不是Samsung的SDMMC控制器驱动的问题，这个得以后看看，此时的patch如下：

diff --git a/arch/arm/boot/dts/exynos4412-tiny4412.dts b/arch/arm/boot/dts/exynos4412-tiny4412.dts
index 69a0d5d..ad8b2ba 100644
--- a/arch/arm/boot/dts/exynos4412-tiny4412.dts
+++ b/arch/arm/boot/dts/exynos4412-tiny4412.dts
@@ -75,7 +75,21 @@
         compatible = "smsc,usb4640";
         reset-gpios = <&gpm2 4 GPIO_ACTIVE_LOW>;
         initial-mode = <USB4640_MODE_HUB>;
-    };
+    };
+
+    regulators {
+        compatible = "simple-bus";
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        mmc_reg: regulator@0{
+            compatible = "regulator-fixed";
+            reg = <0>;
+            regulator-name = "VMEM_VDD_2.8V";
+            regulator-min-microvolt = <2800000>;
+            regulator-max-microvolt = <2800000>;
+        };
+    };
 };

 &rtc {
@@ -86,7 +100,8 @@
     bus-width = <4>;
     pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>;
     pinctrl-names = "default";
-    status = "disabled";
+    vmmc-supply = <&mmc_reg>;
+    status = "okay";
 };

 &serial_0 {

可以下面的两个参考文件，其中对设置mmc控制器的设备树属性进行了介绍。

Documentation/devicetree/bindings/mmc/samsung-sdhci.txt

Documentation/devicetree/bindings/mmc/mmc.txt

下面是Linux启动时检测到sdcard的log：

[    2.238481] s3c-sdhci 12530000.sdhci: clock source 2: mmc_busclk.2 (100000000 Hz)
[    2.245749] s3c-sdhci 12530000.sdhci: Got CD GPIO
[    2.250721] s3c-sdhci 12530000.sdhci: No vqmmc regulator found
[    2.285341] mmc0: SDHCI controller on samsung-hsmmc [12530000.sdhci] using ADMA
[    2.285548] Synopsys Designware Multimedia Card Interface Driver
[    2.287669] usbcore: registered new interface driver usbhid
[    2.287723] usbhid: USB HID core driver
[    2.290841] NET: Registered protocol family 10
[    2.291451] sit: IPv6 over IPv4 tunneling driver
[    2.295264] NET: Registered protocol family 17
[    2.299165] NET: Registered protocol family 15
[    2.303746] Registering SWP/SWPB emulation handler
[    2.309720] hctosys: unable to open rtc device (rtc0)
[    2.325428] ALSA device list:
[    2.325464]   No soundcards found.
[    2.326127] RAMDISK: gzip image found at block 0
[    2.360265] usb 2-2: new high-speed USB device number 2 using exynos-ehci
[    2.468324] EXT4-fs (ram0): mounted filesystem witdered data mode. Opts: (null)
[    2.468418] VFS: Mounted root (ext4 filesystem) on device 1:0.
[    2.468545] devtmpfs: mounted
[    2.468819] Freeing unused kernel memory: 436K (c07e3000 - c0850000)
[    2.490598] usb 2-2: New USB device found, idVendor=0424, idProduct=2640
[    2.490671] usb 2-2: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[    2.491880] hub 2-2:1.0: USB hub found
[    2.492094] hub 2-2:1.0: 3 ports detected
[    2.519078] mmc0: new high speed SDHC card at address b368
[    2.524690] mmcblk0: mmc0:b368 SMI   3.71 GiB
[    2.526964]  mmcblk0: p1

查看系统gpio资源分配情况

[root@tiny4412 ]# cat /sys/kernel/debug/gpio 
......
GPIOs 90-96, platform/11000000.pinctrl, gpk1:

GPIOs 97-103, platform/11000000.pinctrl, gpk2:
 gpio-99  (                    |cd                  ) in  lo IRQ

......
GPIOs 143-147, platform/11000000.pinctrl, gpm2:
 gpio-147 (                    |usb4640 reset       ) out hi    

GPIOs 148-155, platform/11000000.pinctrl, gpm3:

GPIOs 156-163, platform/11000000.pinctrl, gpm4:
 gpio-156 (                    |?                   ) out lo    
 gpio-157 (                    |?                   ) out hi    
 gpio-158 (                    |?                   ) out hi    
 gpio-159 (                    |?                   ) out hi    

......

查看系统interrupt资源使用情况

[root@tiny4412 ]# cat /proc/interrupts 
           CPU0       CPU1       CPU2       CPU3       
 36:          0          0          0          0       GIC  89 Edge      mct_comp_irq
 37:       4039       1439       1133       2185       GIC  28 Edge      MCT
 44:         34          0          0          0       GIC 107 Edge      mmc0
 45:          1          0          0          0       GIC 103 Edge      12480000.hsotg, 12480000.hsotg, dwc2_hsotg:usb1
 46:        266          0          0          0       GIC 102 Edge      ehci_hcd:usb2, ohci_hcd:usb3
 47:         77          0          0          0       GIC  84 Edge      13800000.serial
 51:          1          0          0          0       GIC  67 Edge      12680000.pdma
 52:          0          0          0          0       GIC  68 Edge      12690000.pdma
 53:          0          0          0          0       GIC  66 Edge      12850000.mdma
 65:          0          0          0          0       GIC  79 Edge      11400000.pinctrl
 66:          1          0          0          0       GIC  78 Edge      11000000.pinctrl
 84:          0          0          0          0  COMBINER  80 Edge      3860000.pinctrl
 85:          0          0          0          0       GIC 104 Edge      106e0000.pinctrl
 96:          1          0          0          0  exynos_gpio_irq_chip   2 Edge      12530000.sdhci cd
IPI0:          0          1          1          1  CPU wakeup interrupts
IPI1:          0          0          0          0  Timer broadcast interrupts
IPI2:        853       1531        516        580  Rescheduling interrupts
IPI3:          0          3          3          3  Function call interrupts
IPI4:          0          1          1          1  Single function call interrupts
IPI5:          0          0          0          0  CPU stop interrupts
IPI6:          0          0          0          0  IRQ work interrupts
IPI7:          0          0          0          0  completion interrupts
Err:          0

 代码已经上传到github上了：

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