I don't know what the BWB unit is, I guess W is for write and one of the
Bs is for burst. All I know is that there repeatedly have been issues
with it hanging on certain streams (ENGR00223231, ENGR00293425), with
various firmware versions, sometimes blocking something related to the
GDI bus or the GDI AXI adapter. There are some error cases that we don't
know how to recover from without a reboot. Apparently this unit can be
disabled by setting bit 12 in the FRAME_MEM_CTRL mailbox register to
zero, so do that to avoid crashes.

Side effects are reduced burst lengths when writing out decoded frames
to memory, so there is an "enable_bwb" module parameter to turn it back
on.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>