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AM3517 MMC root device

Rainier Lamers
Prodigy 220 points

Other Parts Discussed in Thread: AM3517

I'm trying to port Linux (AM3517-evm) to my custom board. First time I'm working with Linux so bear with me please.

EVM uses MMC1 to boot, my board uses MMC2. I managed to get u-boot working with MMC2 and it loads the Kernel. Kernel is doing quite OK but it is getting stuck waiting for mmcblk0p2 to become ready.

My question is: How does the Kernel determine which MMC device to use to mount the root file system ? I'm guessing it is trying to use MMC1. There are no console statements anywhere referring to the MMC device used so that does not help.

Rainier

  • 0
    Prodigy 220 points

    Starting to dawn on me. I need mmcblk1p2.

    Trouble is, there is no such thing in the /dev folder. How do I get this thing to boot from MMC2 ? I'm sure it can't be that hard - can it ?

    Anybody can point me in the direction how to proceed ? I'm intending connecting a eMMC to MMC2 and need to boot from that. I have a traditional SD card wired here for now which contains the root files (easier to use a traditional card for development work).

  • 0 in reply to Rainier Lamers
    Guru 26430 points

    No experience with the AM3517. Isn't that just changing the root parameter in the u-boot bootargs environment variable?

  • 0 in reply to Norman Wong
    Prodigy 220 points

    Perhaps - but so far no luck.

    Changing mmcblk0p2 to mmcblk1p2 just results in the console output that it is now waiting for mmcblk1p2.

    I have disabled all the card detection in the MMC driver (the card is never removed). Using printk statements I can see that the Kernel is testing both card detects (MMC1 and MMC2) - sometimes I get a line saying MMC0: trying to init card (there is no card on MMC1).

    I'll get there. Seems it just is a matter of hacking away. Thank goodness for printk. That is a life saver.

    Figured how to create the mmcblc1p2 node file - needs Major node of 129 and Minor of 10 so that is OK now.

  • 0 in reply to Rainier Lamers
    Prodigy 220 points

    OK, two minutes after typing the above I got it working.

    It works if I insert a SD card into MMC1 as well (just a blank one). It now mounts root on MMC2 and gets on with it.

    Close now...

    Rainier