drm/msm: Add SDM845 DPU support

SDM845 SoC includes the Mobile Display Sub System (MDSS) which is a
top level wrapper consisting of Display Processing Unit (DPU) and
display peripheral modules such as Display Serial Interface (DSI)
and DisplayPort (DP).

MDSS functions essentially as a back-end composition engine. It blends
video and graphic images stored in the frame buffers and scans out the
composed image to a display sink (over DSI/DP).

The following diagram represents hardware blocks for a simple pipeline
(two planes are present on a given crtc which is connected to a DSI
connector):

       MDSS
      +---------------------------------+
      | +-----------------------------+ |
      | | DPU                         | |
      | |  +--------+  +--------+     | |
      | |  |  SSPP  |  |  SSPP  |     | |
      | |  +----+---+  +----+---+     | |
      | |       |           |         | |
      | |  +----v-----------v---+     | |
      | |  |  Layer Mixer (LM)  |     | |
      | |  +--------------------+     | |
      | |  +--------------------+     | |
      | |  |    PingPong (PP)   |     | |
      | |  +--------------------+     | |
      | |  +--------------------+     | |
      | |  |  INTERFACE (VIDEO) |     | |
      | |  +---+----------------+     | |
      | +------|----------------------+ |
      |        |                        |
      | +------|---------------------+  |
      | |      | DISPLAY PERIPHERALS |  |
      | |  +---v-+      +-----+      |  |
      | |  | DSI |      |  DP |      |  |
      | |  +-----+      +-----+      |  |
      | +----------------------------+  |
      +---------------------------------+

The number of DPU sub-blocks (i.e. SSPPs, LMs, PP blocks and INTFs)
depends on SoC capabilities.

Overview of DPU sub-blocks:
---------------------------
* Source Surface Processor (SSPP):
 Refers to any of hardware pipes like ViG, DMA etc. Only ViG pipes are
 capable of performing format conversion, scaling and quality improvement
 for source surfaces.

* Layer Mixer (LM):
 Blend source surfaces together (in requested zorder)

* PingPong (PP):
 This block controls frame done interrupt output, EOL and EOF generation,
 overflow/underflow control.

* Display interface (INTF):
 Timing generator and interface connecting the display peripherals.

DRM components mapping to DPU architecture:
------------------------------------------
PLANEs maps to SSPPs
CRTC maps to LMs
Encoder maps to PPs, INTFs

Data flow setup:
---------------
MDSS hardware can support various data flows (e.g.):
  - Dual pipe: Output from two LMs combined to single display.
  - Split display: Output from two LMs connected to two separate
                   interfaces.

The hardware capabilities determine the number of concurrent data paths
possible. Any control path (i.e. pipeline w/i DPU) can be routed to any
of the hardware data paths. A given control path can be triggered,
flushed and controlled independently.

Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rajesh Yadav <ryadav@codeaurora.org>
Signed-off-by: Sravanthi Kollukuduru <skolluku@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>