MIPI DSI Tool

VisionFive 2 supports two MIPI display output channel, one is 1C2L (2-lane MIPI DSI), and the other is 1C4L (4-lane MIPI DSI). StarFive provides the tool package dsi_tool for you to calculate DSI timing. This topic describes how to use the tool for timing calculation and set the timing into the Linux driver to light the screen.

About DSI Tool Package

The DSI tool package includes the following components:
  • StarFive_DSI_Tool_v2.0.exe
  • input.md: Stores input for MIPI DSI timing calculate. This file provides example parameters for your reference.
  • output.txt: This file is the timing result generated by running ./run.sh based on input.md.
  • ./run.sh: Script used to generate output.txt

Prepare Timing Calculate Input

Configure the input.md file to update the timing calculate parameters according to your screen specifications.

The following table describes the parameters in the input.md file:
Table 1. Timing Calculate Input Parameters
Parameter Description
bpp Bit per pixel
pixelclock* The pixel clock
hactive* Horizontal effective pixels
hfront_porch* Horizontal front porch, delay before horizontal synchronization signal
hback_porch* Horizontal back porch, delay after horizontal synchronization signal
hsync_len* Horizontal pulse width, the length of the horizontal synchronization signal
vactive* Vertical effective pixels
vfront_porch* Vertical front porch, delay before vertical synchronization signal
vback_porch* Vertical back porch, delay after vertical synchronization signal
vsync_len* Vertical pulse width, the length of the vertical synchronization signal
dlanes MIPI DSI lane number
dsi_hblank_ratio The ratio of hsa, hbp, and hfp of DSI timing. It is used to allocate the horizontal blanking of the final calculated DSI timing, which can be 0. If any of the three values are 0, the default ratio is used.
r_hsa The ratio of hsa of DSI timing, which can be 0. If the value is 0, the DSI hsa, hbp, hfp will use the default ratio.
r_hbp The ratio of hbp of DSI timing, which can be 0. If the value is 0, the DSI hsa, hbp, hfp will use the default ratio.
r_hfp The ratio of hfp of DSI timing, which can be 0. If the value is 0, the DSI hsa, hbp, hfp will use the default ratio.
pixclk_source Pixel clock source, corresponding to PLL2 of JH-7110 (default is 1188M). To make changes to PLL2, you will have to modify this parameter.
Note: * means you shall obtain the parameter values from the screen manufacturer.

Generate DSI Timing Result

Run the following command to generate the output.txt file which contains the DSI timing calculate result. The result is calculated based on your input.md.
./run.sh
The following is an example output:
Figure 1. Example Output

Apply Timing to IC2L MIPI Channel

Apply the timing calculation result to the IC2L MIPI channel.

  1. To support a new screen for the 1C2L MIPI channel, modify the driver file starfive_drm_seeedpanel.c under /Linux/drivers/gpu/drm/verisilicon.

    This driver file servers as an i2c device by default, and the probe interface uses the i2c command to read the panel ID, and verify whether the current screen is connected properly based on the return value. When debugging a new screen:
    • If the i2c command can read the panel ID, the probe function needs to support the i2c interface; In seed_ panel_ enable function, the panel should be enabled according to the specific command of i2c.
    • If the i2c command cannot read panel ID, you are recommended to remove the i2c related command, then the probe process can be completed, so that the screen is in connected status by default.
      Note: It is necessary to remove all i2c read/write command.
  2. Add dpi_timing, which is the timing of the panel, in the panel driver. It corresponds to starfive_drm_seedpanel.c under the \linux\drivers\gpu\drm\verisilicon, which maps to seeed_panel_modes.
    1. Enter starfive_drm_seedpanel.c file.
    2. Modify the parameters of PLL 1188M under this function according to the output.txt file.
      Figure 2. 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. After configuration, it is synchronized to the DC controller driver and MIPI DSI driver. For example, to set the lanes to 1, you can change the corresponding parameters in the input file.
      Figure 3. Example Input
      The corresponding driver code is shown in the following figure:
      Figure 4. Driver Code
  3. Follow the steps below to configure MIPI DSI.
    1. Open the starfive_drm_dsi.c file under the path of \linux\drivers\gpu\drm\verisilicon in Linux.
    2. Locate the cdns_dsi_mode2cfg function and set hsa, hbp and hfp in channel 0 to 36, 108, 288 respectively.
      Note: Modifying parameters should based on the corresponding channel. 1C2L corresponds to channel 0 while 1C4L corresponds to channel 1.
      Figure 5. hsa hbp hfp
    3. Locate the cdns_dsi_adjust_phy_config function and set the bitrate to 750000000.
      Figure 6. Bitrate
      Tip: The hs_clk_rate in the figure means bitrate.

Apply Timing to IC4L MIPI Channel

Apply the timing calculation result to the IC4L MIPI channel.

  1. To support a new screen for the 1C4L MIPI channel, modify the driver file panel-jadard-jd9365da-h3.c under /Linux/drivers/gpu/drm/panel.

    This driver file servers as an i2c device by default, and the probe interface uses the i2c command to read the panel ID, and verify whether the current screen is connected properly based on the return value. When debugging a new screen:
    • If the i2c command can read the panel ID, the probe function needs to support the i2c interface; In seed_ panel_ enable function, the panel should be enabled according to the specific command of i2c.
    • If the i2c command cannot read panel ID, you are recommended to remove the i2c related command, then the probe process can be completed, so that the screen is in connected status by default.
      Note: It is necessary to remove all i2c read/write command.
  2. Add dpi_timing, which is the timing of the panel, in the panel driver. It corresponds to cz101b4001_desc under the \linux\drivers\gpu\drm\panel.
    1. Enter starfive_drm_seedpanel.c file.
    2. Modify the parameters of PLL 1188M under this function according to the output.txt file.
      Figure 7. 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. After configuration, it is synchronized to the DC controller driver and MIPI DSI driver. For example, to set the lanes to 4, you can change the corresponding parameters in the input file. The corresponding driver code is shown in the following figure:
      Figure 8. Driver Code
  3. Follow the steps below to configure MIPI DSI.
    1. Open the starfive_drm_dsi.c file under the path of \linux\drivers\gpu\drm\verisilicon in Linux.
    2. Locate the cdns_dsi_mode2cfg function and set hsa, hbp and hfp in channel 1 to 66, 64, and 57 respectively.
      Note: Modifying parameters should based on the corresponding channel. 1C2L corresponds to channel 0 while 1C4L corresponds to channel 1.
      Figure 9. hsa hbp hfp
    3. Locate the cdns_dsi_adjust_phy_config function and set the bitrate to 750000000.
      Figure 10. Bitrate
      Tip: The hs_clk_rate in the figure means bitrate.