DisplayPort IP Core Transmits Unexpected Last Pixel Data At the End of Every Video Line

The DisplayPort TX core may transmit video with unexpected last pixel data at every end of video line for certain combination of resolution and color depth. This issue may occur when the total symbols (TS) required to transmit active pixel data per line per lane is not in multiple of SYMBOLS_PER_CLOCK (2 or 4).

This issue is caused by the flaw in the packetizer array indexing.

The total symbols required per line per lane (TS) across color depths can be calculated as:

16 bpp: TS = (active pixels per line x (4 x 1) / 2) / lane count

18 bpp: TS = (active pixels per line x (4 x 9) / 16) / lane count

20 bpp: TS = (active pixels per line x (4 x 5) / 8) / lane count

24 bpp: TS = (active pixels per line x (4 x 3) / 4) / lane count

30 bpp: TS = (active pixels per line x (4 x 15) / 16) / lane count

32 bpp: TS = (active pixels per line x (4 x 2) / 2) / lane count

36 bpp: TS = (active pixels per line x (4 x 9) / 8) / lane count

48 bpp: TS = (active pixels per line x (4 x 3) / 3) / lane count

For a resolution example of 1,368 active pixels per line, 30 bpp and lane count of 2, the total symbols required per line per lane is

1,368 x (4 x 15) / 16 / 2 = 2565

The value of 2,565 is not a multiple of 2 or 4. This means you may observe unexpected last pixel data at the end of every video line.

There is no workaround for this issue.

This issue is fixed in version 16.0 of the DisplayPort IP core.