Switching framebuffer data lines for IMX8MM

[rajvikamdar]

Hi Team

I am trying to use 2 MIPI DSI LCD connected IMX8MM processor.

I am using a switcher in between to toggle the display between the two. As of now I am able to blank and unblank both the screens. But I want that both the LCDs remain active at the same time. Like the framebuffer data lines be allocated to each of the LCDs.

How can I modify the FB driver to allocate data lines to each of the LCDs individually? Can you help me with the same?

[joanxie]

what switcher do you use? did you connect switcher to the mipi dsi? i.mx8 series don't support framebuffer driver anymore

[rajvikamdar]

Hi @joanxie 

We are using mipi dsi switcher FSA641-D from ON semiconductor. 

I am not getting how can I switch writing on fb0 from the driver or userspace.

So that the same image can be displayed on LCD after continuous switching between the two LCDs.

MiPI switch works on chip select line, of CS =0 then LCD A will be selected and CS=1

[joanxie]

i.mx8mm only one input buffer up to 1080p, I think you can use duplicates screens, but refer to your document, it seems that you want to use seperate display, I don't think imx8mm could support it,

[rajvikamdar]

@joanxie 

Can you tell me how can I use duplicate screens?

And which part of the driver code executes writing DSI from userspace fb0?

[joanxie]

I don't have such sample code, for imx8mm, don't use frame buffer driver anymore, you can refer to the mipi dsi driver as below:

https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/gpu/drm/imx/sec_mipi_dsim-imx.c?h=...

[rajvikamdar]

Hi @joanxie 

Can we by any means switch the input buffer? When the image writes on the buffer, we want to switch at that point of time?

Is that possible?

[joanxie]

I mean that maybe the third party bridge can support duplicates screens, for imx8mm, only one display controller which couldn't support two displays