On the AM3517, MMC2 is special in that it can drive an external transceiver. During boot from MMC2, the controller assumes that the external transceiver is in place and that the CLK is externally delayed to compensate for the transceiver's delay.
By setting CONTROL_DEVCONF1[MMCSDIO2ADPCLKISEL] = 1 in the kernel I can access the eMMC but the bit is not set during booting from MMC2.
Is there a way to get the MMC2 to boot without using an external transceiver? http://processors.wiki.ti.com/index.php/SD-MMC_Usage_Notes_on_AM35x
PROBLEM: The Wiki page seems to contradict the technical reference manual. In section 24.4.7.6 it says the following: 1.8V or 3.3V I/O voltage on PORT 2. External transceiver mode on PORT 2 is not supported. If the external transceiver is not used the ROM must set CONTROL_DEVCONF1[MMCSDIO2ADPCLKISEL] = 1
Can anyone explain this?