SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
In order to interface with peripherals which can support a different data rate than the VP output, a Merge-Split-Sync (MSS) module is introduced between the VP outputs and DISPC final output. When interfacing with a peripheral which can support a higher data rate than the VP, two VP outputs can be merged to generate one high data rate stream on the DISPC output (MERGE mode). When interfacing with a peripheral which requires dual physical links to support a high resolution video, one VP output can be split into two half data rate pixel streams on two separate DISPC outputs (SPLIT mode).
Both left/right (L/R) or odd/even (O/E) pixel selection types are supported.
Additionally, the MSS module can also operate in a SYNC mode where two VP outputs get the same source pixel clock. The SYNC mode only affects the clock muxing and does not manipulate the data going out of each VP output.
Only the following configurations, as shown in Figure 12-368, are supported:
The DSS0_COMMON_DISPC_MSS_VP1 and DSS0_COMMON_DISPC_MSS_VP3 registers control the MSS operation.
The MSS line buffers are sized to support up to 6K RGB30 video data. Therefore, in MERGE use-case, two 3K VP outputs can be merged to create a 6K output at DISPC. In SPLIT use-case, one 6K output can be split into two 3K outputs.
In both, MERGE and SPLIT use-cases, all the control signals (VS, HS, DE) are re-generated so as to match with the timing of the new merged frame or split frames.
For Merge-Split-Sync mode of operation, the VP outputs need to be programmed to be active-high for the different signals (DE, VS, HS). For SPLIT mode of operation, it is required that the total number of pixels in a line is a multiple of 2. For both SPLIT mode and SYNC mode of operation, both the VP blocks need to be enabled at the same cycle. This is achieved by making a single write to the global enable register (DSS0_COMMON_DISPC_GLOBAL_OUTPUT_ENABLE[3-0] VP_ENABLE field).
When the DISPC is interfaced with the DP/eDP peripheral, the SPLIT mode corresponds to the Split (single stream transport) mode of operation of the DSC (Digital Stream Compression) sub-module within the EDP module. In this case, the two streams at half the pixel clock rate are first provided to DSC_ENC0 and DSC_ENC1 within the EDP. Then, the combined encoded stream is provided to the EDP MHDPTX Controller VIF0 port. The SYNC mode corresponds to the Dual (multi stream transport) mode of operation of the EDP module. In this case, the two streams at full pixel clock rate are provided to the EDP VIF0 and VIF1 ports (the EDP DSC has to be bypassed in this mode). For more details, see the EDP Section 12.6.5.2.1, Video Stream Clock/Data Muxing.