linux/drivers/gpu/drm/sti/NOTES
Benjamin Gaignard 30ebb9088c drm: sti: add bindings for DRM driver
Add DRM/KMS driver bindings documentation.
Describe the required properties for each of the hardware IPs drivers.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Rob Clark <robdclark@gmail.com>
2014-07-30 18:11:53 +02:00

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1. stiH display hardware IP
---------------------------
The STMicroelectronics stiH SoCs use a common chain of HW display IP blocks:
- The High Quality Video Display Processor (HQVDP) gets video frames from a
video decoder and does high quality video processing, including scaling.
- The Compositor is a multiplane, dual-mixer (Main & Aux) digital processor. It
has several inputs:
- The graphics planes are internally processed by the Generic Display
Pipeline (GDP).
- The video plug (VID) connects to the HQVDP output.
- The cursor handles ... a cursor.
- The TV OUT pre-formats (convert, clip, round) the compositor output data
- The HDMI / DVO / HD Analog / SD analog IP builds the video signals
- DVO (Digital Video Output) handles a 24bits parallel signal
- The HD analog signal is typically driven by a YCbCr cable, supporting up to
1080i mode.
- The SD analog signal is typically used for legacy TV
- The VTG (Video Timing Generators) build Vsync signals used by the other HW IP
Note that some stiH drivers support only a subset of thee HW IP.
.-------------. .-----------. .-----------.
GPU >-------------+GDP Main | | +---+ HDMI +--> HDMI
GPU >-------------+GDP mixer+---+ | :===========:
GPU >-------------+Cursor | | +---+ DVO +--> 24b//
------- | COMPOSITOR | | TV OUT | :===========:
| | | | | +---+ HD analog +--> YCbCr
Vid >--+ HQVDP +--+VID Aux +---+ | :===========:
dec | | | mixer| | +---+ SD analog +--> CVBS
'-------' '-------------' '-----------' '-----------'
.-----------.
| main+--> Vsync
| VTG |
| aux+--> Vsync
'-----------'
2. DRM / HW mapping
-------------------
These IP are mapped to the DRM objects as following:
- The CRTCs are mapped to the Compositor Main and Aux Mixers
- The Framebuffers and planes are mapped to the Compositor GDP (non video
buffers) and to HQVDP+VID (video buffers)
- The Cursor is mapped to the Compositor Cursor
- The Encoders are mapped to the TVOut
- The Bridges/Connectors are mapped to the HDMI / DVO / HD Analog / SD analog
FB & planes Cursor CRTC Encoders Bridges/Connectors
| | | | |
| | | | |
| .-------------. | .-----------. .-----------. |
+------------> |GDP | Main | | | +-> | | HDMI | <-+
+------------> |GDP v mixer|<+ | | | :===========: |
| |Cursor | | | +-> | | DVO | <-+
| ------- | COMPOSITOR | | |TV OUT | | :===========: |
| | | | | | | +-> | | HD analog | <-+
+-> | HQVDP | |VID Aux |<+ | | | :===========: |
| | | mixer| | +-> | | SD analog | <-+
'-------' '-------------' '-----------' '-----------'