RGB not showing proper over MIPI DSI intrerface IMX8MM

[rajvikamdar]

Hi Team

We are using IMX8MM processor and connect LCD screen over MIPI DSI interface. But somehow we are not getting proper color coding for the same.

1. We have used RGB565 format to configure the lcd screen with 16bpp. MIPI_DSI_FMT_RGB565.

2. We tried one application where we are writing the display with R,G and B values. Out of that on R value is getting set G and B values are not getting reflected at all.

3. If Green and Blue is set then we are getting complete black color.

4. If Red, Green and blue all are set then also we are getting only red color.

Can you help us debug this further. All the help is appreciated.

[rajvikamdar]

Few more questions:

1. When we set the controller panel to RGB565 format we are able to display Red and Green images perfectly on the LCD screen, but blue image is turning into Black and not able to see any image there.

2. When we set the controller panel to BGR565 format we are able to display blue and green properly but we are not able to see Red image at all.

Can you please help us to resolve this issue?

Somehow the last 8 bits are getting ignored and the lcd panel is not able to capture it

[rajvikamdar]

Hi Igor

Thanks for the response. Can you please help me understand if IMX8MM supports single lane mipi dsi?

Our LCD supports single lane mipi dsi. Please find attached datasheet.

[igorpadykov]

lane configuration can be adjusted in parameter "dsi-lanes = < >;"

https://source.codeaurora.org/external/imx/linux-imx/tree/arch/arm64/boot/dts/freescale/imx8mm-ddr4-...

Best regards
igor

[igorpadykov]

Hi rajvikamdar

as starting point one can look at rm67191 driver

https://source.codeaurora.org/external/imx/linux-imx/tree/arch/arm64/boot/dts/freescale/imx8mm-ddr4-...

https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/gpu/drm/panel/panel-raydium-rm6719...

pay attention to custom lcd initialization:

* There is no description in the Reference Manual about these commands.
* We received them from vendor, so just use them as is.
*/
static const struct cmd_set_entry mcs_rm67191[] = {

and  correct timings in: struct drm_display_mode default_mode = {..

Best regards
igor