DS90UB941AS-Q1: DS90UB941A&DS90UB948 Abnormal display when powered on for the first time

In addition, when a fault occurs, the value of the dphy register 0xf is 0x3f, and the values ​​of the dlane registers 0x10-0x13 are all 0x10

Hi Alon,

Thanks for sharing this issue.

Can you share who customer is and which project?

I will need some further details to get a better understanding of the issue:

1) Have you successfully brought up 948 Deserializer PATGEN? And 941 Serializer PATGEN?

2) Are you operating in dual DSI or single DSI port?

3) What is the failure rate? 

Alon Chen said:

After the problem occurs on the first power-up, it persists until the power is cycled.The problem does not occur on the first power-up, and it remains until the power is cycled

Can you clarify how often and when it fails? 

4) Can you try a soft reset on Serializer and Deserializer and see if anything improves?

5) Are you using TI EVMs in this setup?

Here are some further register data needed to properly root cause the issue:

• Main Page:
  • General_cfg 0x7
• DSI registers:
  • DSI_SYNC_STATUS 0x15
  • DSI_STATUS 0X28
  • DSI_ERR_COUNT 0x29

Some suggestions to try while we collect more information:

• Soft reset Main Page 0x1[0]
• Try DSI register 0x21 DSI_NO_EOTPKT = 1 
• Try varying DSI clocking mode Main Page 0x4F[7] and 0x56[1:0]
  • please list what setting error occurred in and vary to a different setting
  • Ensure SOC can match setting for continuous and discontinuous clock modes

Thanks,

Ragav Subramanian

Hi Ragav，

Thank you for your support.

A leading global bus manufacturer (full name withheld for confidentiality). Smart cockpit project products.
1) Have you successfully brought up 948 Deserializer PATGEN? And 941 Serializer PATGEN?

Reply: The fault also reproduces in PATGEN mode.

2) Are you operating in dual DSI or single DSI port?

Reply: single DSI

3) What is the failure rate?

Alon Chen said:
After the problem occurs on the first power-up, it persists until the power is cycled.The problem does not occur on the first power-up, and it remains until the power is cycled
Can you clarify how often and when it fails?

Reply: Occurs once per 10 power-ups, representing a failure rate of approximately 10%.

4) Can you try a soft reset on Serializer and Deserializer and see if anything improves?

Reply: During fault reproduction, resetting the serializer may occasionally resolve the issue. However, when the fault is present, resetting the serializer may also occasionally trigger the fault (10% failure rate). Resetting the deserializer has no effect.

5) Are you using TI EVMs in this setup?

Reply: No evaluation version is currently available.

Here are some further register data needed to properly root cause the issue:

------------------
Main Page:
General_cfg 0x7
DSI registers:
DSI_SYNC_STATUS 0x15
DSI_STATUS 0X28
DSI_ERR_COUNT 0x29
Some suggestions to try while we collect more information:

Soft reset Main Page 0x1[0]
Try DSI register 0x21 DSI_NO_EOTPKT = 1
Try varying DSI clocking mode Main Page 0x4F[7] and 0x56[1:0]
please list what setting error occurred in and vary to a different setting
Ensure SOC can match setting for continuous and discontinuous clock modes

Reply:
1. Our register configuration is as shown in the diagram below.
2. This fault also occurs when switching from the currently set continuous clock mode to discontinuous mode.
Register readback value:

DSI_SYNC_STATUS 0x15 0x00
DSI_STATUS 0x28 0x05
DSI_ERR_COUNT 0x29 0xff
Tried:
Soft reset: Set main page 0x1 register to 0x01 for reset. Symptoms occur intermittently with no improvement.

DSI register 0x21 DSI_NO_EOTPKT = 1: According to register definition, this only disables error alerts. Not attempted.

Tried varying DSI clocking mode (Main Page 0x4F[7] and 0x56[1:0]):
The fault also occurs when 0x4F is set to discontinuous mode alone. Setting 0x56 to any mode other than DSI reference clock mode prevents normal display.