ARM: mvebu: don't set the PL310 in I/O coherency mode when I/O coherency is disabled

Since commit f2c3c67f00 (merge commit that adds commit "ARM: mvebu:
completely disable hardware I/O coherency"), we disable I/O coherency
on Armada EBU platforms.

However, we continue to initialize the coherency fabric, because this
coherency fabric is needed on Armada XP for inter-CPU
coherency. Unfortunately, due to this, we also continued to execute
the coherency fabric initialization code for Armada 375/38x, which
switched the PL310 into I/O coherent mode. This has the effect of
disabling the outer cache sync operation: this is needed when I/O
coherency is enabled to work around a PCIe/L2 deadlock. But obviously,
when I/O coherency is disabled, having the outer cache sync operation
is crucial.

Therefore, this commit fixes the armada_375_380_coherency_init() so
that the PL310 is switched to I/O coherent mode only if I/O coherency
is enabled.

Without this fix, all devices using DMA are broken on Armada 375/38x.

Signed-off-by: Thomas Petazzoni <[email protected]>
Acked-by: Gregory CLEMENT <[email protected]>
Tested-by: Gregory CLEMENT <[email protected]>
Signed-off-by: Andrew Lunn <[email protected]>
Cc: <[email protected]> # v3.8+

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