Analysis method for abnormal location of LCD display

First case:

After entering kernel or Android, if the LCM image shows an exception, you can use the following steps to determine the level at which the problem occurs.

Step1: Use DMMs to determine if there is a problem with the data that is being brushed into the LCM. If there is no problem with the picture obtained by DMMs, the problem can be basically located in LCM Driver/module, and timing.

Step2: If there is a problem with the data obtained in Step1 DMMs, you need to crawl framebuffer data to further analyze adb shell cat/dev/graphics/fb0 >/data/fb.bin and then fb.bin through ADB Push out, view Fb.bin step3 by tool: If you see a problem with fb.bin data, the problem usually occurs when the LCD control does overlay. If you have no problem viewing framebuffer data, you need to locate the analysis next. STEP5: This step requires that you continue to crawl SF layerdump and run the Sf_layerdump.bat script directly. If there is a problem with the dump image, it should be a problem when drawing the layer data and need to analyze a single app. If surface data is not a problem, then the problem needs to be located in the Surfaceflinger module.

The second case: if the LK start stage shows abnormal, such as the Phone boot logo interface display abnormal.

1). You can first replace the logo image with a simple left black right white equal size picture, such as:

When the normal display is measured separately, the relevant MIPI timing diagram is displayed when the anomaly is shown.

The waveform of d0p/n during normal display are as follows:

The waveform of d0p/n is shown as follows:

From the waveform above, it is known that the data sent by the system is often abnormal, and is often shown to be abnormal. Need to look for specific reasons for the platform side.

2). Send instructions directly from the IC side to brush the image to the screen, without the platform output image. The same operation, if the display problem can not be reproduced, should belong to the platform side data display exception.

Like Novatek nt35596 from the beginning of the first to make the Reg run, do not send 0x11,0x29 instructions.

Send the following from the IC Brush image instructions:

{0xff,1,{0x05}},

{Regflag_delay, 5, {}}

{0xea,1,{0xff}}

{0XEB,1,{0X27}}

{0XEC,1,{0X01}}

Analysis method for abnormal location of LCD display