Itop4412開發板emmc驅動移植（裝置樹）
硬體裝置：itop4412開發板 核心版本linux-3.8.1
裝置樹方式減少了裝置的冗餘編碼，同時使移植變得更加高效。eMMC作為開發板的基礎，十分重要。
裝置樹用的是核心自帶的smdk4412.dts
vim arch/arm/boot/dts/exynos4412-smdk4412.dts
在裝置樹中新增如下程式碼：
87 ldo22_reg: LDO22 { 88 regulator-name = "VMEM_VDD_2.8V"; 89 regulator-min-microvolt = <2800000>; 90 regulator-max-microvolt = <2800000>; 91 maxim,ena-gpios = <&gpk0 2 1>; 92 };
146 [email protected] { 147 compatible = "samsung,exynos4412-dw-mshc"; 148 reg = <0x12550000 0x1000>; 149 interrupts = <0 77 0>; 150 #address-cells = <1>; 151 #size-cells = <0>; 152 fifo-depth = <0x80>; 153 clocks = <&clock 301>, <&clock 149>; 154 clock-names = "biu", "ciu"; 155 num-slots = <1>; 156 broken-cd; 157 non-removable; 158 card-detect-delay = <200>; 159 vmmc-supply = <&ldo22_reg>; 160 clock-frequency = <400000000>; 161 samsung,dw-mshc-ciu-div = <0>; 162 samsung,dw-mshc-sdr-timing = <2 3>; 163 samsung,dw-mshc-ddr-timing = <1 2>; 164 pinctrl-0 = <&sd4_clk &sd4_cmd &sd4_bus4 &sd4_bus8>; 165 pinctrl-names = "default"; 166 status = "okay"; 167 bus-width = <8>; 168 cap-mmc-highspeed; 169 };
在驅動中增加裝置屬性匹配：
vim drivers/mmc/host/dw_mmc-exynos.c
221 static const struct of_device_id dw_mci_exynos_match[] = { 222 { .compatible = "samsung,exynos4412-dw-mshc",}, 223 { .compatible = "samsung,exynos5250-dw-mshc", 224 .data = &exynos5250_drv_data, }, 225 {}, 226 };
make menuconfig 配置emmc核心驅動
編譯燒寫進開發板後啟動會出現錯誤：
mmc1: unrecognised EXT_CSD revision 7
解決方法：將296行的6改為7
vim drivers/mmc/core/mmc.c
295 /* amended by cqx:6->7 */
296 if (card->ext_csd.rev > 7) {
297 pr_err("%s: unrecognised EXT_CSD revision %d\n",
298 mmc_hostname(card->host), card->ext_csd.rev);
299 err = -EINVAL;
300 goto out;
301 }重新編譯後燒寫入開發板，啟動列印如下資訊說明emmc驅動移植成功。
mmcblk0: mmc1:0001 4YMD3R 3.64 GiB
mmcblk0boot0: mmc1:0001 4YMD3R partition 1 4.00 MiB
mmcblk0boot1: mmc1:0001 4YMD3R partition 2 4.00 MiB
mmcblk0: p1 p2 p3 p4
mmcblk0boot1: unknown partition table
mmcblk0boot0: unknown partition table
mmc0: mmc_rescan_try_freq: trying to init card at 1562500 Hz
mmc0: new high speed SD card at address 0260
使用fdisk -l命令檢視詳細資訊
Disk /dev/mmcblk0: 3909 MB, 3909091328 bytes
226 heads, 33 sectors/track, 1023 cylinders
Units = cylinders of 7458 * 512 = 3818496 bytes
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 653 1020 1372272 c Win95 FAT32 (LBA)
/dev/mmcblk0p2 6 287 1051578 83 Linux
/dev/mmcblk0p3 288 569 1051578 83 Linux
/dev/mmcblk0p4 570 652 309507 83 Linux
Partition table entries are not in disk order
Disk /dev/mmcblk0boot1: 4 MB, 4194304 bytes
4 heads, 16 sectors/track, 128 cylinders
Units = cylinders of 64 * 512 = 32768 bytes
Disk /dev/mmcblk0boot1 doesn't contain a valid partition table
Disk /dev/mmcblk0boot0: 4 MB, 4194304 bytes
4 heads, 16 sectors/track, 128 cylinders
Units = cylinders of 64 * 512 = 32768 bytes
Disk /dev/mmcblk0boot0 doesn't contain a valid partition table
Disk /dev/mmcblk1: 1992 MB, 1992294400 bytes
4 heads, 16 sectors/track, 60800 cylinders
Units = cylinders of 64 * 512 = 32768 bytes