A15 is a SMP capable SoC and K2G uses an SMP capable SoC in a
uni-processor configuration. As a result of this, we had originally
expected to disable CONFIG_SMP and manage to get a slight boost
performance wise. However, as the program progressed, the following
surprising behavior was observed.

Disabling CONFIG_SMP causes the Kernel's default cache allocation
strategy to change from is switched from "write-allocate" to
"write-back". This causes hardware blocks such as USB, PCIe write
operations to become non-coherent from A15's perspective.

However, all of the following are treated identically in A15:
Write-back, Read-Write Allocate Write-back, Read Allocate Write-back,
Write Allocate

Write-back, No Allocate > This is a somewhat specialized type which we
doubt comes into play here.

All of the following write-thru options are treated as non-cacheable
in A15: Write-thru, Read-Write Allocate Write-thru, Read Allocate
Write-thru, Write Allocate Write-thru, No Allocate

Based on the TLB captures taken with and without CONFIG_SMP, it was
evaluated that that the properties used should NOT have a coherence
issue.

Since the issue is still under debug, we must choose to enable
CONFIG_SMP for KS2 generation devices as a temporary work around.
Final decision if a proper workaround is provided OR if coherence
needs to be disabled overall for KS2* devices is yet to be finalized.

Reported-by: Roger Quadros
Reported-by: Bin Liu
Reported-by: Murali Karicheri
Signed-off-by: Nishanth Menon