media: s5p-mfc: Add support for V4L2_MEMORY_DMABUF type

media: s5p-mfc: Add support for V4L2_MEMORY_DMABUF type

MFC driver supports only MMAP operation mode mainly due to the hardware
restrictions of the addresses of the DMA buffers (MFC v5 hardware can
access buffers only in 128MiB memory region starting from the base address
of its firmware). When IOMMU is available, this requirement is easily
fulfilled even for the buffers located anywhere in the memory - typically
by mapping them in the DMA address space as close as possible to the
firmware. Later hardware revisions don't have this limitations at all.

The second limitation of the MFC hardware related to the memory buffers
is constant buffer address. Once the hardware has been initialized for
operation on given buffer set, the addresses of the buffers cannot be
changed.

With the above assumptions, a limited support for USERPTR and DMABUF
operation modes can be added. The main requirement is to have all buffers
known when starting hardware. This has been achieved by postponing
hardware initialization once all the DMABUF or USERPTR buffers have been
queued for the first time. Once then, buffers cannot be modified to point
to other memory area.

This patch also removes unconditional USERPTR operation mode from encoder
video node, because it doesn't work with v5 MFC hardware without IOMMU
being enabled.

In case of MFC v5 a bidirectional queue flag has to be enabled as a
workaround of the strange hardware behavior - MFC performs a few writes
to source data during the operation.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
[mszyprow: adapted to v4.14 code base, rewrote and extended commit message,
 added checks for changing buffer addresses, added bidirectional queue
 flags and comments]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>