Configuration Example

This section provides an example to configure the parameters in kernel. The following code block is an example of the output file:
{
.dpi_timing = {
        .pixelclock   = 148500000, //div 10, 60 fps
        .hactive      = 1920, //w
        .hfront_porch = 88,
        .hback_porch  = 148,
        .hsync_len    = 44,
        .vactive      = 1080, //h
        .vfront_porch = 34,
        .vback_porch  = 6,
        .vsync_len    = 5,
    },
    .dsi_timing = {
        .dlanes       = 4,
        .bitrate      = 900000000,
        .hsa          = 147,//132,
        .hbp          = 480,//508,
        .hfp          = 280,//268,
        .hact         = 5760,
    },
},

To Configure eDP

dpi_timing is the timing of the eDP, which needs to be added in the panel driver. It corresponds to jh7110_lt8911exb.c under the path of \linux\drivers\gpu\drm\verisilicon, which maps lt8911exb_panel_modes.
  1. Enter jh7110_lt8911exb.c file.
  2. Modify the parameters of PLL 1188M under this function according to the output file.
    Figure 1. Modify the Parameters
    Tip:
    • clock = pixelclock/1000
    • hdisplay = hactive
    • hsync_start = hactive + hfp
    • hsync_end = hactive + hfp + hbp
    • htotal = hactive + hfp + hbp+ hsync_len
    • vdisplay = vactive
    • vsync_start = vactive + vfp
    • vsync_end = vactive + vfp + vbp
    • vtotal = vactive + vfp + vbp + vsync_len
  3. Perform the following to update the MIPI_Timing[] parameters:
    static int MIPI_Timing[] =
// hfp, hs,     hbp,    hact,   htotal, vfp,    vs,     vbp,    vact,   vtotal, pixel_CLK/10000
//-----|---|------|-------|--------|-----|-----|-----|--------|--------|---------------
{88, 44, 148, 1920, 2200, 34, 5, 6, 1080, 1125, 15000};   // boe config for linux
    Figure 2. MIPI_Timing[]
  4. After configuration, it will be synchronized to the DC controller driver and eDP DSI driver. For example, to update DSI_Timing lanes to 4, you can change the corresponding parameters in the input file.
    The corresponding driver code is shown in the following screen:
    Figure 3. driver_code

To Configure MIPI DSI

The following is the DSI timing in output.txt we generated before. Follow the steps below to configure MIPI DSI.
.dsi_timing = {
        .dlanes       = 4,
        .bitrate      = 900000000,
        .hsa          = 147,//132,
        .hbp          = 480,//508,
        .hfp          = 280,//268,
        .hact         = 5760,
    },
  1. Open jh7110_lt8911exb.c file under the path of \linux\drivers\gpu\drm\verisilicon in Linux. In JH-7110 DevKit, the channel number of eDP is channel 0.
  2. Locate cdns_dsi_mode2cfg function to modify the hsa, hbp and hfp parameter according to the value in the output.txt generated previously.
    Figure 4. hsa hbp hfp
  3. Then locate cdns_dsi_adjust_phy_config function to modify the bitrate parameter according to the value in the output.txt generated previously.
    Figure 5. bitrate
    Tip: The hs_clk_rate in the figure means bitrate.