The eMMC card read/write test is failing on Zynq in Vivado 2015.3.
The test will fail while reading the EXT_CSD register to check for high speed mode support.
When an eMMC card is switching to High speed mode, the driver sends cmd6 which expects an R1b response.
So the driver needs to poll for the "Transfer Complete" bit in the Normal Interrupt Status register to make sure that there is no DAT line busy.
This code is missing in the 2015.3 build and the delay provided after cmd6 is not sufficient.
To fix the issue, copy the following two files into the specified folder in the 2015.3 installation:
Copy the files into \SDK\2015.3\data\embeddedsw\XilinxProcessorIPLib\drivers\sdps_v2_5\src\
This issue is fixed in Vivado 2015.4.