media: imx: Fix field negotiation

media: imx: Fix field negotiation

IDMAC interlaced scan, a.k.a. interweave, should be enabled in the
IDMAC output channels only if the IDMAC output pad field type is
'seq-bt' or 'seq-tb', and field type at the capture interface is
'interlaced*'.

V4L2_FIELD_HAS_BOTH() macro should not be used on the input to determine
enabling interlaced/interweave scan. That macro includes the 'interlaced'
field types, and in those cases the data is already interweaved with
top/bottom field lines.

The CSI will capture whole frames when the source specifies alternate
field mode. So the CSI also enables interweave for alternate input
field type and the field type at capture interface is interlaced.

Fix the logic for setting field type in try_fmt in CSI entity.
The behavior should be:

- No restrictions on field type at sink pad.

- At the output pads, allow sequential fields in TB order, if the sink pad
  field type is sequential or alternate. Otherwise passthrough the field
  type from sink to source pad.

Move this logic to new function csi_try_field().

These changes result in the following allowed field transformations
from CSI sink -> source pads (all other field types at sink are passed
through to source):

seq-tb -> seq-tb
seq-bt -> seq-tb
alternate -> seq-tb

In a future patch, the CSI sink -> source will allow:

seq-tb -> seq-bt
seq-bt -> seq-bt
alternate -> seq-bt

This will require supporting interweave with top/bottom line swapping.
Until then seq-bt is not allowed at the CSI source pad because there is
no way to swap top/bottom lines when interweaving to INTERLACED_BT --
note that despite the name, INTERLACED_BT is top-bottom order in memory.
The BT in this case refers to field dominance: the bottom lines are
older in time than the top lines.

The capture interface device allows selecting IDMAC interweave by
choosing INTERLACED_TB if the CSI/PRPENCVF source pad is seq-tb and
INTERLACED_BT if the source pad is seq-bt (for future support of seq-bt).

Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>