Some uSD cards on USDHC-3 do not boot on a DualLite i.MX6. It seems as if the cards do not response fast enough after power up. In fact the data sheet of the failing cards says that it might take up to 1 second to be able to respond to the first ACMD41.
Is there any information about the detailed steps of the ROM boot code and which timing needs to be observed by the boot media? I didn't find any information in the reference manual, the data sheet and the hardware development guide.
At the moment we see that behaviour with one type of SD cards. But we don't know how safe we are with the others. Is it just some milliseconds margin which might not work at high or low temperatures?