5.1.6. 常见问题¶
5.1.6.1. MMC 初始化失败¶
5.1.6.1.1. 现象¶
Linux启动后，在扫描mmc0设备的时候报错“whilst initialising MMC card”，log如下
mmc_host mmc1: Bus speed (slot 0) = 204000000Hz (slot req 300000Hz, actual 300000HZ div = 680)
mmc_host mmc0: Bus speed (slot 0) = 204000000Hz (slot req 25000000Hz, actual 20400000HZ div = 10)
mmc_host mmc1: Bus speed (slot 0) = 204000000Hz (slot req 200000Hz, actual 200000HZ div = 1020)
mmc0: error -110 whilst initialising MMC card
mmc_host mmc0: Bus speed (slot 0) = 204000000Hz (slot req 300000Hz, actual 300000HZ div = 680)
mmc_host mmc1: Bus speed (slot 0) = 204000000Hz (slot req 100000Hz, actual 100000HZ div = 2040)
mmc_host mmc0: Bus speed (slot 0) = 204000000Hz (slot req 25000000Hz, actual 20400000HZ div = 10)
mmc0: error -110 whilst initialising MMC card
mmc_host mmc0: Bus speed (slot 0) = 204000000Hz (slot req 200000Hz, actual 200000HZ div = 1020)
random: fast init done
mmc_host mmc0: Bus speed (slot 0) = 204000000Hz (slot req 25000000Hz, actual 20400000HZ div = 10)
mmc0: error -110 whilst initialising MMC card
mmc_host mmc0: Bus speed (slot 0) = 204000000Hz (slot req 100000Hz, actual 100000HZ div = 2040)
5.1.6.1.2. 原因分析¶
首先确认 DTS 中sdmcx节点中的参数 clock-frequency 有没有更改过；
由于 DDR 和 SDMC 共用了一个父时钟，需要确认是否改了DDR工作频率导致了父时钟发生变化。
上述出错log就是因为原因2，修改了DDR频率为 408MHz，导致MMC工作时钟不准。