How to solve conflicts between BB Black GPMC port and eMMC
Posted: Sun Jul 07, 2013 8:44 pm
It's not possible to use the GPMC directly on BB Black due to pinmuxing conflicts (there is an eMMC memory attached to MMC1, which overlaps with GPMC_AD[0:7]). Theoretically it should be possible to boot via an SD card on MMC0. For this purpose SYSBOOT[0:4] pullups/pulldowns should be changed according to the table on page 6 of the BB Black schematics, from 11100b to 11000b. eMMC can be held in reset by modifying MLO/u-Boot so that GPMC_A4 is pinmuxed to GPIO and driven high (eMMC_RSTn signal). The bad news is that GPMC_A4 is not available on the expansion headers. A check should also be made of the state of eMMC I/O signals when the chip is in reset. eMMC pullups may also need to be removed.
http://e2e.ti.com/support/arm/sitara_ar ... spx#957962
http://e2e.ti.com/support/arm/sitara_ar ... spx#957962