drm/meson AmLogic Meson Video Processing Unit

VPU Handles the Global Video Processing, it includes management of the clocks gates, blocks reset lines and power domains.

What is missing :

  • Full reset of entire video processing HW blocks
  • Scaling and setup of the VPU clock
  • Bus clock gates
  • Powering up video processing HW blocks
  • Powering Up HDMI controller and PHY

Video Processing Unit

The Amlogic Meson Display controller is composed of several components that are going to be documented below:

DMC|---------------VPU (Video Processing Unit)----------------|------HHI------|
   | vd1   _______     _____________    _________________     |               |
D  |-------|      |----|            |   |                |    |   HDMI PLL    |
D  | vd2   | VIU  |    | Video Post |   | Video Encoders |<---|-----VCLK      |
R  |-------|      |----| Processing |   |                |    |               |
   | osd2  |      |    |            |---| Enci ----------|----|-----VDAC------|
R  |-------| CSC  |----| Scalers    |   | Encp ----------|----|----HDMI-TX----|
A  | osd1  |      |    | Blenders   |   | Encl ----------|----|---------------|
M  |-------|______|----|____________|   |________________|    |               |
___|__________________________________________________________|_______________|

Video Input Unit

VIU Handles the Pixel scanout and the basic Colorspace conversions We handle the following features :

  • OSD1 RGB565/RGB888/xRGB8888 scanout
  • RGB conversion to x/cb/cr
  • Progressive or Interlace buffer scanout
  • OSD1 Commit on Vsync
  • HDR OSD matrix for GXL/GXM

What is missing :

  • BGR888/xBGR8888/BGRx8888/BGRx8888 modes
  • YUV4:2:2 Y0CbY1Cr scanout
  • Conversion to YUV 4:4:4 from 4:2:2 input
  • Colorkey Alpha matching
  • Big endian scanout
  • X/Y reverse scanout
  • Global alpha setup
  • OSD2 support, would need interlace switching on vsync
  • OSD1 full scaling to support TV overscan

Video Post Processing

VPP Handles all the Post Processing after the Scanout from the VIU We handle the following post processings :

  • Postblend, Blends the OSD1 only
    We exclude OSD2, VS1, VS1 and Preblend output
  • Vertical OSD Scaler for OSD1 only, we disable vertical scaler and
    use it only for interlace scanout
  • Intermediate FIFO with default Amlogic values

What is missing :

  • Preblend for video overlay pre-scaling
  • OSD2 support for cursor framebuffer
  • Video pre-scaling before postblend
  • Full Vertical/Horizontal OSD scaling to support TV overscan
  • HDR conversion

Video Encoder

VENC Handle the pixels encoding to the output formats. We handle the following encodings :

  • CVBS Encoding via the ENCI encoder and VDAC digital to analog converter
  • TMDS/HDMI Encoding via ENCI_DIV and ENCP
  • Setup of more clock rates for HDMI modes

What is missing :

  • LCD Panel encoding via ENCL
  • TV Panel encoding via ENCT

VENC paths :

       _____   _____   ____________________
vd1---|     |-|     | | VENC     /---------|----VDAC
vd2---| VIU |-| VPP |-|-----ENCI/-ENCI_DVI-|-|
osd1--|     |-|     | | \                  | X--HDMI-TX
osd2--|_____|-|_____| |  |\-ENCP--ENCP_DVI-|-|
                      |  |                 |
                      |  \--ENCL-----------|----LVDS
                      |____________________|

The ENCI is designed for PAl or NTSC encoding and can go through the VDAC directly for CVBS encoding or through the ENCI_DVI encoder for HDMI. The ENCP is designed for Progressive encoding but can also generate 1080i interlaced pixels, and was initialy desined to encode pixels for VDAC to output RGB ou YUV analog outputs. It’s output is only used through the ENCP_DVI encoder for HDMI. The ENCL LVDS encoder is not implemented.

The ENCI and ENCP encoders needs specially defined parameters for each supported mode and thus cannot be determined from standard video timings.

The ENCI end ENCP DVI encoders are more generic and can generate any timings from the pixel data generated by ENCI or ENCP, so can use the standard video timings are source for HW parameters.

Video Canvas Management

CANVAS is a memory zone where physical memory frames information are stored for the VIU to scanout.

Video Clocks

VCLK is the “Pixel Clock” frequency generator from a dedicated PLL. We handle the following encodings :

  • CVBS 27MHz generator via the VCLK2 to the VENCI and VDAC blocks
  • HDMI Pixel Clocks generation

What is missing :

  • Genenate Pixel clocks for 2K/4K 10bit formats

Clock generator scheme :

 __________   _________            _____
|          | |         |          |     |--ENCI
| HDMI PLL |-| PLL_DIV |--- VCLK--|     |--ENCL
|__________| |_________| \        | MUX |--ENCP
                          --VCLK2-|     |--VDAC
                                  |_____|--HDMI-TX

Final clocks can take input for either VCLK or VCLK2, but VCLK is the preferred path for HDMI clocking and VCLK2 is the preferred path for CVBS VDAC clocking.

VCLK and VCLK2 have fixed divided clocks paths for /1, /2, /4, /6 or /12.

The PLL_DIV can achieve an additional fractional dividing like 1.5, 3.5, 3.75… to generate special 2K and 4K 10bit clocks.

HDMI Video Output

HDMI Output is composed of :

  • A Synopsys DesignWare HDMI Controller IP
  • A TOP control block controlling the Clocks and PHY
  • A custom HDMI PHY in order convert video to TMDS signal
 ___________________________________
|            HDMI TOP               |<= HPD
|___________________________________|
|                  |                |
|  Synopsys HDMI   |   HDMI PHY     |=> TMDS
|    Controller    |________________|
|___________________________________|<=> DDC

The HDMI TOP block only supports HPD sensing. The Synopsys HDMI Controller interrupt is routed through the TOP Block interrupt. Communication to the TOP Block and the Synopsys HDMI Controller is done a pair of addr+read/write registers. The HDMI PHY is configured by registers in the HHI register block.

Pixel data arrives in 4:4:4 format from the VENC block and the VPU HDMI mux selects either the ENCI encoder for the 576i or 480i formats or the ENCP encoder for all the other formats including interlaced HD formats. The VENC uses a DVI encoder on top of the ENCI or ENCP encoders to generate DVI timings for the HDMI controller.

GXBB, GXL and GXM embeds the Synopsys DesignWare HDMI TX IP version 2.01a with HDCP and I2C & S/PDIF audio source interfaces.

We handle the following features :

  • HPD Rise & Fall interrupt
  • HDMI Controller Interrupt
  • HDMI PHY Init for 480i to 1080p60
  • VENC & HDMI Clock setup for 480i to 1080p60
  • VENC Mode setup for 480i to 1080p60

What is missing :

  • PHY, Clock and Mode setup for 2k && 4k modes
  • SDDC Scrambling mode for HDMI 2.0a
  • HDCP Setup
  • CEC Management