Porting the MIPI DSI panel driver to Uboot on iMX8M Mini

[kailas_kharse]

Hello,

We have our customized ST7703 panel, which we have successfully ported at the kernel layer with VAR-DART-MX8MM and the same is working fine. As we want to enable the splash screen, we tried to port the same driver at the uboot layer, based on the rm67191 reference panel driver.

Our LCD is connected directly to the MIPI DSI interface. Post porting, we are able to see that the probe and initialization of panel is going correct, logs as attached. But the MIPI clock and lcdif clock registers are not getting set.

We strongly feel that there is some issue with the clock settings at the uboot level. Following are the differences of the register values at the kernel and uboot level.

Register	Register addr	Kernel Layer	Uboot Layer
LCDIF_CTRL1	0x10	0x3072100	0x70100
LCDIF_CUR_BUF	0x40	0x0 to 0x78100000	0xbf000000
LCDIF_NEXT_BUF	0x50	0x78100000	0xbf000000
LCDIF_VDCTRL0	0x70	0x10300003	0x11300003

As mentioned above these are the value dumps between the kernel layer and uboot layer. And as communicated on the portal, without changing these registers variscite is able to use the RM67191 panel, then why do we need to change these register settings. We have tried your following commit id:

https://github.com/varigit/uboot-imx/commit/71b9c57a9327d3bf0d7d0235cc849632c1704793

And we are using the uboot version: imx_v2020.04_5.4.24_2.1.0_var02

Thanks,
Kailas

[sd05]

Hello @jamesbone 

I have a similar requirement as @kailas_kharse but i don't want to display the splash screen at early stage.

I am having a DART-IMX8MM based customboard.

I want to display the bmp images after we get uboot CLI prompt using bmp display.

I have managed to initialise panel and all the register values are set to proper everything goes alright still I am not able to get display.

There is no doubt on init sequence as it is working in kernel. 

Using all pixel on command of ST7703 we are able to get the all pixel on. Still what we write on frame buffer is not updated on panel and bmp command is also not working.

Getting something like this in logs on giving bmp display.

u-boot=> bmp d $splashimage
video_bmp_display() hdr_size=40, bmp_bpix=24
video_bmp_display() Display-bmp: 800 x 480 with 16777216 colours, display 1

please guide what is getting wrong.

Need  urgent help on this. 

Thanks in advance!

[Hardevsinh_Palaniya]

Hi @sd05 and @kailas_kharse  ,
I am facing the same issue in u-boot on iMX8M mini while display is working in kernel.

Have you resolved the issue?
Can you share how to ON all pixel?

Are you able to bring-up the display in u-boot?

Appreciate any help.

[kailas_kharse]

Additional pending parches as limits were reached.

Patch P1.patch to P5.patch in a previous thread.
P6.patch to P7.patch is attached here.

I hope this will help you.

Regards,
Kailas Kharse

[kailas_kharse]

Hello,

@Hardevsinh_Palaniya ,

 I was able to resolve the issue and able to display the splash image on the boot screen in u-boot.
There are many changes that need to do as there is no support for MIPI in U-boot.

I am attaching the patches which will help you to resolve your issue, follow patches in sequence.

[Hardevsinh_Palaniya]

Hi @kailas_kharse ,

Thanks a lot for providing patches , appreciate this help.

I have tried these patches in my system however no luck, nothing gets displayed in u-boot,

Can you help address below questions,

1. I could see some hard-coded numbers like in pixel clock etc, so will they work on any display or its specific to your panel only.

2. If they are hard-coded as per your panel, can you suggest or guide what are the changes I should make in patches ?

3. Still in my case it not working in u-boot but is working in kernel so any debug suggestions ? currently the issue is raydium panel so I am uncertain about the DSI support in u-boot.

4. Even after running raydium panel's working support , any way to know that DSI support is enabled or not ?

Any help would be greatly appreciable.

[kailas_kharse]

Hello,

Sending the final patches that we integrated into our product.

Apply in sequence from 01 to 05. patch.

[jamesbone]

i.MX8MM, the SPL / DDR calibration is taking time before the U-Boot splash screen is displayed. The DDR frequency is so high that DDR calibration must be done before U-Boot, or system may cannot boot normally.  If you want to config splash screen from SRAM before DDR is configured, you have to initalize display controller (CONFIG_VIDEO and  CONFIG_IMX_SEC_MIPI_DSI) and show logo (CONFIG_VIDEO_LOGO) in SPL stage, which I think is almost impossible.