powerpc/powernv: replace the hard coded boundary with gate

At the moment 64bit-prefetchable window can be maximum 64GB, which is
currently got from device tree. This means that in shared mode the maximum
supported VF BAR size is 64GB/256=256MB. While this size could exhaust the
whole 64bit-prefetchable window. This is a design decision to set a
boundary to 64MB of the VF BAR size. Since VF BAR size with 64MB would
occupy a quarter of the 64bit-prefetchable window, this is affordable.

This patch replaces magic limit of 64MB with "gate", which is 1/4 of the
M64 Segment Size(m64_segsize >> 2) and adds comment to explain the reason
for it.

Signed-off-by: Wei Yang <[email protected]>
Reviewed-by: Gavin Shan <[email protected]>
Acked-by: Alexey Kardashevskiy <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>

0 files changed, 0 insertions, 0 deletions