Upscaling for the Chrontel CH7308 LVDS Transmitters

The Intel^® EMGD can upscale lower-resolution modes (those smaller than the size of the respective panel) to the native size of the panel connected to a Chrontel CH7308* LVDS transmitter.

The Intel^® EMGD uses a user-supplied DTD with the native flag set (also known as native DTD) as native timing for the panel connected to either a CH7308 transmitter.

If the user does not supply a native DTD, the Intel^® EMGD takes the first available matching FP info width and height timings as native timing for the panel if standard timings were selected as part of edid_avail or edid_not_avail flags.

To support upscaling, the LVDS transmitters require setting the pipe to native timing of the panel despite the user-selected resolution. It also requires finding the native timing (also known as native DTD) of the panel based on user-supplied configuration information.

The CH7308 (sDVO) port drivers limit the list of supported modes to the size of panel. The port drivers also mark one of the timings as native DTD as follows (it goes to the next step only if native DTD is not found in the current step).

1. It finds the timing with the user-defined DTD with the native DTD flag set. This becomes the native DTD for the panel.

2. If the panel is an EDID panel and user selected to use EDID DTDs, then the port driver marks the EDID DTD as native DTD.

3. If the user supplies a DTD without the native DTD flag set, then the port driver marks this one as the native DTD.

4. If none of the above steps works, the port driver finds the first matching timing for FP width, height and marks it as native DTD.

If none of the above steps work, then there is no native DTD and no upscaling is performed.