DS90UB941AS-Q1: LCD does not display

Hello Abraham,

Can you confirm what type of DSI mode this is? Burst, non-burst pulse, or non-burst event mode? Also can you confirm if the DSI clock is continuous or non-continuous?

Please try the following:

1. Configure the pattern generator to show the working screen using internal timing and internal clock 

2. Try configuring the pattern generator for internal timing with external clock using the PGCFG register 0x65[3]

3. Report results 

4. Configure the pattern generator for external timing/external clock by also adjusting 0x65[2]

5. Report results 

Best Regards,

Casey 

Hi Casey,

thanks for your qucik reply.

Yes, I use DSI continus clock. the device tree confisg as below:

dsi,flags = <(MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST | MIPI_DSI_MODE_LPM)>;
dsi,format = <MIPI_DSI_FMT_RGB888>;
dsi,lanes = <4>;
dsi,channel = <0>;

display-timings {
native-mode = <&boe_timing0>;

boe_timing0: timing0 {
clock-frequency = <65000000>;
hactive = <1280>;
vactive = <800>;
hfront-porch = <30>;
hsync-len = <10>;
hback-porch = <10>;
vfront-porch = <3>;
vsync-len = <5>;
vback-porch = <4>;
hsync-active = <0>;
vsync-active = <0>;
de-active = <0>;
pixelclk-active = <0>;
};
};

I can use internal/external clock & internal/external timing generate the color bar. But when disable pattern gernerator, the lcd displays as the attachment. It shows the debian desktop abnormally.

The status registers showed that the dphy data lane2 EOT sync error. Is it the reason of lcd display.

update the registers.

ds90ub941 dsi reg 0 = 0
ds90ub941 dsi reg 1 = 0
ds90ub941 dsi reg 2 = 0
ds90ub941 dsi reg 3 = 1d
ds90ub941 dsi reg 4 = 14
ds90ub941 dsi reg 5 = c
ds90ub941 dsi reg 6 = 0
ds90ub941 dsi reg 7 = 0
ds90ub941 dsi reg 8 = 0
ds90ub941 dsi reg 9 = 0
ds90ub941 dsi reg a = 0
ds90ub941 dsi reg b = 0
ds90ub941 dsi reg c = 0
ds90ub941 dsi reg d = 0
ds90ub941 dsi reg e = 0
ds90ub941 dsi reg f = 3f
ds90ub941 dsi reg 10 = 0
ds90ub941 dsi reg 11 = 0
ds90ub941 dsi reg 12 = 10
ds90ub941 dsi reg 13 = 0
ds90ub941 dsi reg 14 = 0
ds90ub941 dsi reg 15 = 0
ds90ub941 dsi reg 16 = 0
ds90ub941 dsi reg 17 = 0
ds90ub941 dsi reg 18 = 0
ds90ub941 dsi reg 19 = 0
ds90ub941 dsi reg 1a = 0
ds90ub941 dsi reg 1b = 0
ds90ub941 dsi reg 1c = 0
ds90ub941 dsi reg 1d = 0
ds90ub941 dsi reg 1e = 0
ds90ub941 dsi reg 1f = 0
ds90ub941 dsi reg 20 = 71
ds90ub941 dsi reg 21 = 60
ds90ub941 dsi reg 22 = ff
ds90ub941 dsi reg 23 = 7f
ds90ub941 dsi reg 24 = 0
ds90ub941 dsi reg 25 = 0
ds90ub941 dsi reg 26 = 0
ds90ub941 dsi reg 27 = 0
ds90ub941 dsi reg 28 = 1
ds90ub941 dsi reg 29 = ff
ds90ub941 dsi reg 2a = 3e
ds90ub941 dsi reg 2b = 8
ds90ub941 dsi reg 2c = 4
ds90ub941 dsi reg 2d = 0
ds90ub941 dsi reg 2e = 0
ds90ub941 dsi reg 2f = 0
ds90ub941 dsi reg 30 = 0
ds90ub941 dsi reg 31 = 20
ds90ub941 dsi reg 32 = 0
ds90ub941 dsi reg 33 = 4
ds90ub941 dsi reg 34 = 0
ds90ub941 dsi reg 35 = 20
ds90ub941 dsi reg 36 = 1f
ds90ub941 dsi reg 37 = 1f
ds90ub941 dsi reg 38 = 1f
ds90ub941 dsi reg 39 = 0
ds90ub941 dsi reg 3a = 2
ds90ub941 dsi reg 3b = 3

The LCD is operated by the DE only.

Best Regards

Abraham

Hello Abraham,

From your panel configuration is seems like burst mode is being used?

dsi,flags = <(MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST | MIPI_DSI_MODE_LPM)>;

I also don't see any flag indicating that the clock is continuous. For pixel clock from DSI clock mode it is suggested that the DSI mode be either non-burst sync event or non-burst pulse mode. 

Are you saying that the video worked correctly in PATGEN mode with external timing? That is surprising to me given the symptoms here. Can you please over the steps used to program, enable, and disable the pattern generator?

Best Regards,

Casey 

Hi Casey,

The dsi default clock is continuous clock, only flags for non-continuous. 

OK, Remove the BURST flag, the result is same.

Yes, the pattern gernerator is OK used internal or external timing, but when use DSI as the source & external timing, the display is abnormal.

Do you have any suggestion??

Is there any regs for the bit order? 

Thanks

Hi,

Add a message,

Use the color board as desktop background, but the display as the attach.

Thanks

Hello Abraham,

This statement is confusing:

Yes, the pattern gernerator is OK used internal or external timing, but when use DSI as the source & external timing, the display is abnormal.

That's why i was asking if you could provide the exact steps which were used to enable/disable the pattern generator and to use different timings. 

Also is this an 18 or 24 bit color display? The pictures look like there may be a color space problem so one other thing I would suggest trying is setting 0x12[2] = 1

Best Regards,

Casey 

Hi Casey,

Thanks for your suggestion.

It works well, I mean the video display normally. But there is a new problem.

The LCD backlight is too dark, Is there any method to improve it?

The CPU DSI mode is RGB888, and enable 18bit video.

Hello Abraham,

Can you confirm the MAPSEL setting on the 948 deserializer side? Is it high or low?

Best Regards,

Casey 

Hi Casey,

Thanks for your help. See next reply.

Thanks

Hi Casey,

Thanks for your help. You are right, MAPSEL is set H, the lcd display is OK. But I use 941 pattern gernerator to generate colorbar, it is OK and MAPSEL=L/H, Why???

The ds90ub9xx is a nice chip.

Thanks