目前开发遇到了某些SD卡和TI的SOC芯片的驱动不协调的地方，具体表现为：
uboot 阶段初始化mmc dev 1 没有任何串口信息输出，无法读写mmc
Kernel阶段报错”SD卡初始化失败 error -110 whilst initialising SD card“
具体的原因是SD的某些CMD操作不支持，返回-110的错误，需要
uboot阶段，在dts中屏蔽掉：
main_sdhci1: sdhci@4fb0000 {
ti,otap-del-sel-legacy = <0x2>;
/*ti,otap-del-sel-sd-hs = <0xf>;
ti,otap-del-sel-sdr12 = <0xf>;
ti,otap-del-sel-sdr25 = <0xf>;
ti,otap-del-sel-sdr50 = <0xc>;
ti,otap-del-sel-sdr104 = <0x5>;
ti,otap-del-sel-ddr50 = <0xc>;
sdhci-caps-mask = <0x2 0x0>;*/
dma-coherent;
};
Kernel阶段，在drivers/mmc/host/sdhci.c 的函数 void __sdhci_read_caps 中添加：
host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
主要是使能SDHCI_QUIRK2_NO_1_8_V
if (host->quirks2 & SDHCI_QUIRK2_NO_1_8_V) {
host->caps1 &= ~(SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 |
SDHCI_SUPPORT_DDR50);
/*
* The SDHCI controller in a SoC might support HS200/HS400
* (indicated using mmc-hs200-1_8v/mmc-hs400-1_8v dt property),
* but if the board is modeled such that the IO lines are not
* connected to 1.8v then HS200/HS400 cannot be supported.
* Disable HS200/HS400 if the board does not have 1.8v connected
* to the IO lines. (Applicable for other modes in 1.8v)
*/
mmc->caps2 &= ~(MMC_CAP2_HSX00_1_8V | MMC_CAP2_HS400_ES);
mmc->caps &= ~(MMC_CAP_1_8V_DDR | MMC_CAP_UHS);
}
重新编译u-boot和Kernel解决SD卡问题。