CRITICALITY

Low

DESCRIPTION

Any pipe connected to writeback (WB) in memory-to-memory (m2m) mode (DISPC_WB_ATTRIBUTES[19] WRITEBACKMODE = 0x1) cannot be connected on the fly to an active panel when m2m operation is complete. Trying to attempt this will cause sync-lost interrupt and one corrupted frame.

When a pipe is connected to WB pipeline in m2m mode, after m2m operation, it remains enabled. The HW does not disable the pipeline by clearing the enable bit associated with this pipeline(DISPC_VID_ATTRIBUTES[0] ENABLE = 0x0), though it disables the writeback by clearing the WB pipeline enable bit (DISPC_WB_ATTRIBUTES[0] ENABLE = 0x0). If this pipe is then connected to an active panel, the connection will not be synchronized to a frame start. This will result in current frame getting corrupted and sync-lost.

WORKAROUND

The SW should use following exit sequence from m2m operation:

1. When m2m operation is completed and hardware is automatically disabled writeback by setting DISPC_WB_ATTRIBUTES[0] ENABLE bit to 0x0, SW should disable the pipe connected to WB in m2m mode: DISPC_VID_ATTRIBUTES[0] ENABLE = 0x0;
2. Writeback should be re-enabled (DISPC_WB_ATTRIBUTES[0] ENABLE = 0x1) and after that disabled by SW (DISPC_WB_ATTRIBUTES[0] ENABLE = 0x0);
3. The direction of the pipe to the active panel should be changed and all new programming for the pipe should be made;
4. Pipe is enabled again (DISPC_VID_ATTRIBUTES[0] ENABLE = 0x1) at the end.

REVISIONS IMPACTED

SR 2.0A, 2.0, 1.0A, 1.0

TDA3x: 2.0A, 2.0, 1.0A, 1.0

DRA78x: 2.0A, 2.0

DM50x: 2.0