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作者: 彭东林
QQ：405728433
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)）
移植SD卡比较简单，但是刚开始的时候也出现了不少问题，关键是设置设备树的修改、对regulator的理解以及sdcard检测过程。
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，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，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。但是如果直接将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：
1: [ 2.228406] sdhci: Secure Digital Host Controller Interface driver 2: [ 2.233751] sdhci: Copyright(c) Pierre Ossman 3: [ 2.238350] s3c-sdhci 12530000.sdhci: clock source 2: mmc_busclk.2 (100000000 Hz) 4: [ 2.245838] s3c-sdhci 12530000.sdhci: No vmmc regulator found 5: [ 2.251358] s3c-sdhci 12530000.sdhci: No vqmmc regulator found 6: [ 2.257480] ------------[ cut here ]------------ 7: [ 2.261686] kernel BUG at drivers/mmc/host/sdhci.c:1304! 8: [ 2.266981] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM 9: [ 2.272796] Modules linked in: 10: [ 2.275836] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.4.0-gbd7378b-dirty #33 11: [ 2.283038] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) 12: [ 2.289115] task: ef078000 ti: ef080000 task.ti: ef080000 13: [ 2.294500] PC is at sdhci_do_set_ios+0x564/0x5e0 14: [ 2.299189] LR is at arm_heavy_mb+0x1c/0x38 15: [ 2.303351] pc : [<c0406f38>] lr : [<c00198b0>] psr: 80000093 16: [ 2.303351] sp : ef081cc8 ip : 00000200 fp : 00000001 17: [ 2.314807] r10: 00000003 r9 : ef30e800 r8 : 60000013 18: [ 2.320015] r7 : ef30e800 r6 : ef30ec98 r5 : ef30ea34 r4 : ef30eb80 19: [ 2.326525] r3 : 00000001 r2 : 75004180 r1 : 00000000 r0 : ef30eb80 20: [ 2.333036] Flags: Nzcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none 21: [ 2.340240] Control: 10c5387d Table: 4000404a DAC: 00000051 22: [ 2.345969] Process swapper/0 (pid: 1, stack limit = 0xef080210) 23: [ 2.351958] Stack: (0xef081cc8 to 0xef082000) 24: [ 2.356300] 1cc0: 00000000 ef30eb80 00000043 c02d30e8 c02d30e8 00000004 25: [ 2.364460] 1ce0: c0058b5c ef080000 ef1a6ebc c0407168 ef1a6e10 ef1a6e80 c02d30e8 c02d3114 26: [ 2.372619] 1d00: 00000004 c02d465c ef1a6e10 c0852100 c086ea10 c02d46b0 00000000 ef1a6e10 27: [ 2.380778] 1d20: c0852100 c02d54fc eeca0fa0 c00f2934 00000188 eeca0fa0 ef078000 60000013 28: [ 2.388937] 1d40: ef1a6e80 ef1a6e10 ef1a6e80 00000004 60000013 00000000 00000002 ef30ea80 29: [ 2.397096] 1d60: 00000000 c02d56c8 00000000 ef30e800 ef30ea24 60000013 ef080000 c03eff80 30: [ 2.405256] 1d80: eec0b7b8 00000000 ef078000 c0044ee8 00000100 00000200 eec0b6b4 ef30e800 31: [ 2.413415] 1da0: ef30ed2c ef30eb80 ef30e800 00000000 00000200 00000000 ef30ed18 c03f2fd8 32: [ 2.421574] 1dc0: ef30e800 c03f41ac 00000000 c0407ba4 ef264300 ef30eb80 00000808 ef30e800 33: [ 2.429733] 1de0: ef7d3488 00000000 00000000 c03f3dd4 00000000 ef30eb80 00000004 ef1a6e10 34: [ 2.437893] 1e00: ef1a6e00 ef30edec 00000001 ef264110 00000000 c0408be8 05f5e100 c087a810 35: [ 2.446052] 1e20: ef17df50 c087a8a4 5f636d6d 63737562 332e6b6c ee9d9600 00000001 ef1a6e10 36: [ 2.454211] 1e40: fffffffe fffffdfb c087a810 c087a810 00000000 c081683c c0816848 c02ce238 37: [ 2.462370] 1e60: c02ce1e8 ef1a6e10 c08d942c c088e410 00000000 c02cc634 c087a810 ef1a6e44 38: [ 2.470529] 1e80: c088e338 ef1a6e10 c087a810 ef1a6e44 c088e338 00000000 00000000 c02cc8d4 39: [ 2.478688] 1ea0: 00000000 c087a810 c02cc848 c02ca7d4 ef003274 ef17b7c0 c087a810 eebf6f00 40: [ 2.486848] 1ec0: c086ebc8 c02cbb48 c0755dc0 c087a810 c087a810 c0855520 ef267240 c089c000 41: [ 2.495007] 1ee0: c08023cc c02cd0cc c087a7fc c0855520 c0855520 c00097a0 ef15eb00 c0598680 42: [ 2.503166] 1f00: 00000025 0000c000 ef078000 60000013 efffca92 c05aba2c 000000c0 c003da88 43: [ 2.511325] 1f20: 00000001 00000003 c0746c3c c07b1804 00000000 c088c6b8 00000006 00000006 44: [ 2.519484] 1f40: c0858ec8 c0849e3c c084a108 00000006 c089c000 c089c000 c07e35b0 000000c0 45: [ 2.527643] 1f60: c081683c c07e3dec 00000006 00000006 00000000 c07e35b0 ef078000 c0042518 46: [ 2.535802] 1f80: 000000a2 00000000 c058e6c8 00000000 00000000 00000000 00000000 00000000 47: [ 2.543962] 1fa0: 00000000 c058e6d0 00000000 c0010338 00000000 00000000 00000000 00000000 48: [ 2.552121] 1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 49: [ 2.560280] 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000 dffffefb f5fbff7f 50: [ 2.568447] [<c0406f38>] (sdhci_do_set_ios) from [<c0407168>] (sdhci_runtime_resume_host+0x60/0x114) 51: [ 2.577557] [<c0407168>] (sdhci_runtime_resume_host) from [<c02d3114>] (pm_generic_runtime_resume+0x2c/0x38) 52: [ 2.587366] [<c02d3114>] (pm_generic_runtime_resume) from [<c02d465c>] (__rpm_callback+0x2c/0x60) 53: [ 2.596216] [<c02d465c>] (__rpm_callback) from [<c02d46b0>] (rpm_callback+0x20/0x80) 54: [ 2.603942] [<c02d46b0>] (rpm_callback) from [<c02d54fc>] (rpm_resume+0x3ac/0x52c) 55: [ 2.611493] [<c02d54fc>] (rpm_resume) from [<c02d56c8>] (__pm_runtime_resume+0x4c/0x64) 56: [ 2.619482] [<c02d56c8>] (__pm_runtime_resume) from [<c03eff80>] (__mmc_claim_host+0x190/0x19c) 57: [ 2.628161] [<c03eff80>] (__mmc_claim_host) from [<c03f2fd8>] (mmc_start_host+0x38/0x98) 58: [ 2.636232] [<c03f2fd8>] (mmc_start_host) from [<c03f41ac>] (mmc_add_host+0x58/0x7c) 59: [ 2.643957] [<c03f41ac>] (mmc_add_host) from [<c0407ba4>] (sdhci_add_host+0x988/0xe80) 60: [ 2.651855] [<c0407ba4>] (sdhci_add_host) from [<c0408be8>] (sdhci_s3c_probe+0x4a8/0x548) 61: [ 2.660016] [<c0408be8>] (sdhci_s3c_probe) from [<c02ce238>] (platform_drv_probe+0x50/0xac) 62: [ 2.668348] [<c02ce238>] (platform_drv_probe) from [<c02cc634>] (driver_probe_device+0x240/0x454) 63: [ 2.677200] [<c02cc634>] (driver_probe_device) from [<c02cc8d4>] (__driver_attach+0x8c/0x90) 64: [ 2.685626] [<c02cc8d4>] (__driver_attach) from [<c02ca7d4>] (bus_for_each_dev+0x60/0x94) 65: [ 2.693780] [<c02ca7d4>] (bus_for_each_dev) from [<c02cbb48>] (bus_add_driver+0x1b8/0x26c) 66: [ 2.702025] [<c02cbb48>] (bus_add_driver) from [<c02cd0cc>] (driver_register+0x78/0xf8) 67: [ 2.710012] [<c02cd0cc>] (driver_register) from [<c00097a0>] (do_one_initcall+0xbc/0x1f4) 68: [ 2.718176] [<c00097a0>] (do_one_initcall) from [<c07e3dec>] (kernel_init_freeable+0x158/0x1f8) 69: [ 2.726855] [<c07e3dec>] (kernel_init_freeable) from [<c058e6d0>] (kernel_init+0x8/0xf0) 70: [ 2.734927] [<c058e6d0>] (kernel_init) from [<c0010338>] (ret_from_fork+0x14/0x3c) 71: [ 2.742474] Code: e3510000 05991010 ebf24b35 eaffff77 (e7f001f2) 72: [ 2.748557] ---[ end trace 6068c23e2cfdffe9 ]--- 73: [ 2.753149] note: swapper/0[1] exited with preempt_count 1 74: [ 2.758738] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b 75: [ 2.758738] 76: [ 2.767732] CPU1: stopping 77: [ 2.770423] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G D 4.4.0-gbd7378b-dirty #33 78: [ 2.778840] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) 79: [ 2.784927] [<c0016fc0>] (unwind_backtrace) from [<c0013ab8>] (show_stack+0x10/0x14) 80: [ 2.792652] [<c0013ab8>] (show_stack) from [<c01fa9d8>] (dump_stack+0x80/0xc0) 81: [ 2.799851] [<c01fa9d8>] (dump_stack) from [<c0016030>] (handle_IPI+0x1ac/0x1c0) 82: [ 2.807227] [<c0016030>] (handle_IPI) from [<c00094d0>] (gic_handle_irq+0x90/0x94) 83: [ 2.814778] [<c00094d0>] (gic_handle_irq) from [<c0014594>] (__irq_svc+0x54/0x90) 84: [ 2.822240] Exception stack(0xef0aff88 to 0xef0affd0) 85: [ 2.827277] ff80: 00000001 00000000 ef0affe0 c001c860 c05977c8 00000000 86: [ 2.835437] ffa0: 00000000 c084e3c0 c08524b4 c084b2e4 ef0ae000 c08524bc 00000001 ef0affd8 87: [ 2.843594] ffc0: c0010da8 c0010dac 60000013 ffffffff 88: [ 2.848631] [<c0014594>] (__irq_svc) from [<c0010dac>] (arch_cpu_idle+0x38/0x3c) 89: [ 2.856015] [<c0010dac>] (arch_cpu_idle) from [<c0059018>] (cpu_startup_entry+0x1b0/0x26c) 90: [ 2.864256] [<c0059018>] (cpu_startup_entry) from [<4000956c>] (0x4000956c) 91: [ 2.871196] CPU3: stopping 92: [ 2.873888] CPU: 3 PID: 0 Comm: swapper/3 Tainted: G D 4.4.0-gbd7378b-dirty #33 93: [ 2.882305] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) 94: [ 2.888389] [<c0016fc0>] (unwind_backtrace) from [<c0013ab8>] (show_stack+0x10/0x14) 95: [ 2.896113] [<c0013ab8>] (show_stack) from [<c01fa9d8>] (dump_stack+0x80/0xc0) 96: [ 2.903315] [<c01fa9d8>] (dump_stack) from [<c0016030>] (handle_IPI+0x1ac/0x1c0) 97: [ 2.910692] [<c0016030>] (handle_IPI) from [<c00094d0>] (gic_handle_irq+0x90/0x94) 98: [ 2.918243] [<c00094d0>] (gic_handle_irq) from [<c0014594>] (__irq_svc+0x54/0x90) 99: [ 2.925706] Exception stack(0xef0b3f88 to 0xef0b3fd0) 100: [ 2.930743] 3f80: 00000001 00000000 ef0b3fe0 c001c860 c05977c8 00000000 101: [ 2.938902] 3fa0: 00000000 c084e3c0 c08524b4 c084b2e4 ef0b2000 c08524bc 00000001 ef0b3fd8 102: [ 2.947060] 3fc0: c0010da8 c0010dac 60000013 ffffffff 103: [ 2.952096] [<c0014594>] (__irq_svc) from [<c0010dac>] (arch_cpu_idle+0x38/0x3c) 104: [ 2.959476] [<c0010dac>] (arch_cpu_idle) from [<c0059018>] (cpu_startup_entry+0x1b0/0x26c) 105: [ 2.967720] [<c0059018>] (cpu_startup_entry) from [<4000956c>] (0x4000956c) 106: [ 2.974661] CPU2: stopping 107: [ 2.977354] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G D 4.4.0-gbd7378b-dirty #33 108: [ 2.985771] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) 109: [ 2.991854] [<c0016fc0>] (unwind_backtrace) from [<c0013ab8>] (show_stack+0x10/0x14) 110: [ 2.999578] [<c0013ab8>] (show_stack) from [<c01fa9d8>] (dump_stack+0x80/0xc0) 111: [ 3.006781] [<c01fa9d8>] (dump_stack) from [<c0016030>] (handle_IPI+0x1ac/0x1c0) 112: [ 3.014158] [<c0016030>] (handle_IPI) from [<c00094d0>] (gic_handle_irq+0x90/0x94) 113: [ 3.021709] [<c00094d0>] (gic_handle_irq) from [<c0014594>] (__irq_svc+0x54/0x90) 114: [ 3.029171] Exception stack(0xef0b1f88 to 0xef0b1fd0) 115: [ 3.034208] 1f80: 00000001 00000000 ef0b1fe0 c001c860 c05977c8 00000000 116: [ 3.042368] 1fa0: 00000000 c084e3c0 c08524b4 c084b2e4 ef0b0000 c08524bc 00000001 ef0b1fd8 117: [ 3.050525] 1fc0: c0010da8 c0010dac 60000013 ffffffff 118: [ 3.055562] [<c0014594>] (__irq_svc) from [<c0010dac>] (arch_cpu_idle+0x38/0x3c) 119: [ 3.062942] [<c0010dac>] (arch_cpu_idle) from [<c0059018>] (cpu_startup_entry+0x1b0/0x26c) 120: [ 3.071185] [<c0059018>] (cpu_startup_entry) from [<4000956c>] (0x4000956c) 121: [ 3.078130] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b 122: [ 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），我对设备树文件进行了如下修改：
1: diff --git a/arch/arm/boot/dts/exynos4412-tiny4412.dts b/arch/arm/boot/dts/exynos4412-tiny4412.dts 2: index 69a0d5d..b82e303 100644 3: --- a/arch/arm/boot/dts/exynos4412-tiny4412.dts 4: +++ b/arch/arm/boot/dts/exynos4412-tiny4412.dts 5: @@ -75,7 +75,21 @@6: compatible = "smsc,usb4640";
7: reset-gpios = <&gpm2 4 GPIO_ACTIVE_LOW>; 8: initial-mode = <USB4640_MODE_HUB>; 9: - }; 10: + }; 11: + 12: + regulators {13: + compatible = "simple-bus";
14: + #address-cells = <1>; 15: + #size-cells = <0>; 16: + 17: + mmc_reg: regulator@0{18: + compatible = "regulator-fixed";
19: + reg = <0>;20: + regulator-name = "VMEM_VDD_2.8V";
21: + regulator-min-microvolt = <2800000>; 22: + regulator-max-microvolt = <2800000>; 23: + }; 24: + }; 25: }; 26: 27: &rtc { 28: @@ -86,7 +100,10 @@ 29: bus-width = <4>; 30: pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>;31: pinctrl-names = "default";
32: - status = "disabled";
33: + vmmc-supply = <&mmc_reg>; 34: + cd-gpios = <&gpk2 2 GPIO_ACTIVE_HIGH>; 35: + cd-inverted;36: + status = "okay";
37: }; 38: 39: &serial_0 {在参考文件arch/arm/boot/dts/exynos4412-origen.dts中的mmc_reg配置中：
1: regulators {2: compatible = "simple-bus";
3: #address-cells = <1>; 4: #size-cells = <0>; 5: 6: mmc_reg: regulator@0 {7: compatible = "regulator-fixed";
8: reg = <0>;9: regulator-name = "VMEM_VDD_2.8V";
10: regulator-min-microvolt = <2800000>; 11: regulator-max-microvolt = <2800000>; 12: gpio = <&gpx1 1 GPIO_ACTIVE_HIGH>; 13: enable-active-high; 14: }; 15: };可以看到，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，刚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配置删去了，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：
1: cd-gpios = <&gpk2 2 GPIO_ACTIVE_HIGH>; 2: cd-inverted;cd-gpios用于设置sdcard插入拔出检测引脚，从原理图中也可tiny4412使用的是GPIOK2_2，如果这里单独设置了检测引脚，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，此时的patch如下：
1: diff --git a/arch/arm/boot/dts/exynos4412-tiny4412.dts b/arch/arm/boot/dts/exynos4412-tiny4412.dts 2: index 69a0d5d..bd823eb 100644 3: --- a/arch/arm/boot/dts/exynos4412-tiny4412.dts 4: +++ b/arch/arm/boot/dts/exynos4412-tiny4412.dts 5: @@ -75,7 +75,21 @@6: compatible = "smsc,usb4640";
7: reset-gpios = <&gpm2 4 GPIO_ACTIVE_LOW>; 8: initial-mode = <USB4640_MODE_HUB>; 9: - }; 10: + }; 11: + 12: + regulators {13: + compatible = "simple-bus";
14: + #address-cells = <1>; 15: + #size-cells = <0>; 16: + 17: + mmc_reg: regulator@0{18: + compatible = "regulator-fixed";
19: + reg = <0>;20: + regulator-name = "VMEM_VDD_2.8V";
21: + regulator-min-microvolt = <2800000>; 22: + regulator-max-microvolt = <2800000>; 23: + }; 24: + }; 25: }; 26: 27: &rtc { 28: @@ -84,9 +98,12 @@ 29: 30: &sdhci_2 { 31: bus-width = <4>; 32: - pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>; 33: + pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_bus4>;34: pinctrl-names = "default";
35: - status = "disabled";
36: + vmmc-supply = <&mmc_reg>; 37: + cd-gpios = <&gpk2 2 GPIO_ACTIVE_HIGH>; 38: + cd-inverted;39: + status = "okay";
40: }; 41: 42: &serial_0 {在测试时发现，如果不单独设置sdcard的检测引脚的话，在发生sdcard插拔动作时，Linux系统并不能识别到，不知道是不是控制器驱动的问题，这个得以后看看，此时的patch如下：
1: diff --git a/arch/arm/boot/dts/exynos4412-tiny4412.dts b/arch/arm/boot/dts/exynos4412-tiny4412.dts 2: index 69a0d5d..ad8b2ba 100644 3: --- a/arch/arm/boot/dts/exynos4412-tiny4412.dts 4: +++ b/arch/arm/boot/dts/exynos4412-tiny4412.dts 5: @@ -75,7 +75,21 @@6: compatible = "smsc,usb4640";
7: reset-gpios = <&gpm2 4 GPIO_ACTIVE_LOW>; 8: initial-mode = <USB4640_MODE_HUB>; 9: - }; 10: + }; 11: + 12: + regulators {13: + compatible = "simple-bus";
14: + #address-cells = <1>; 15: + #size-cells = <0>; 16: + 17: + mmc_reg: regulator@0{18: + compatible = "regulator-fixed";
19: + reg = <0>;20: + regulator-name = "VMEM_VDD_2.8V";
21: + regulator-min-microvolt = <2800000>; 22: + regulator-max-microvolt = <2800000>; 23: + }; 24: + }; 25: }; 26: 27: &rtc { 28: @@ -86,7 +100,8 @@ 29: bus-width = <4>; 30: pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>;31: pinctrl-names = "default";
32: - status = "disabled";
33: + vmmc-supply = <&mmc_reg>;34: + status = "okay";
35: }; 36: 37: &serial_0 {可以参考文件：
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：
1: [ 2.238481] s3c-sdhci 12530000.sdhci: clock source 2: mmc_busclk.2 (100000000 Hz) 2: [ 2.245749] s3c-sdhci 12530000.sdhci: Got CD GPIO 3: [ 2.250721] s3c-sdhci 12530000.sdhci: No vqmmc regulator found4: [ 2.285341] mmc0: SDHCI controller on samsung-hsmmc [12530000.sdhci] using ADMA
5: [ 2.285548] Synopsys Designware Multimedia Card Interface Driver6: [ 2.287669] usbcore: registered new interface driver usbhid
7: [ 2.287723] usbhid: USB HID core driver 8: [ 2.290841] NET: Registered protocol family 10 9: [ 2.291451] sit: IPv6 over IPv4 tunneling driver 10: [ 2.295264] NET: Registered protocol family 17 11: [ 2.299165] NET: Registered protocol family 15 12: [ 2.303746] Registering SWP/SWPB emulation handler 13: [ 2.309720] hctosys: unable to open rtc device (rtc0) 14: [ 2.325428] ALSA device list: 15: [ 2.325464] No soundcards found. 16: [ 2.326127] RAMDISK: gzip image found at block 017: [ 2.360265] usb 2-2: new high-speed USB device number 2 using exynos-ehci
18: [ 2.468324] EXT4-fs (ram0): mounted filesystem witdered data mode. Opts: (null) 19: [ 2.468418] VFS: Mounted root (ext4 filesystem) on device 1:0. 20: [ 2.468545] devtmpfs: mounted 21: [ 2.468819] Freeing unused kernel memory: 436K (c07e3000 - c0850000) 22: [ 2.490598] usb 2-2: New USB device found, idVendor=0424, idProduct=2640 23: [ 2.490671] usb 2-2: New USB device strings: Mfr=0, Product=0, SerialNumber=0 24: [ 2.491880] hub 2-2:1.0: USB hub found 25: [ 2.492094] hub 2-2:1.0: 3 ports detected26: [ 2.519078] mmc0: new high speed SDHC card at address b368
27: [ 2.524690] mmcblk0: mmc0:b368 SMI 3.71 GiB 28: [ 2.526964] mmcblk0: p1
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
基于tiny4412的Linux内核移植 -- SD卡驱动移植（五）
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原文地址：http://www.cnblogs.com/pengdonglin137/p/5159032.html
