• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 32 subscribers
  • Views 192 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

SN65DSI86: DPTL_LOSS_OF_DP_SYNC_LOCK_EN

SN65DSI86: DPTL_LOSS_OF_DP_SYNC_LOCK_EN, modelines, and non working monitors

Fabrizio Castro
Prodigy 80 points
Part Number: SN65DSI86
Other Parts Discussed in Thread: TEST2

Dear Team,

Thank you for your help so far.

We have now finally received the new revision of the PCB, and we have fixed a couple of bugs in the driver.

The support for the monitor we are using for testing has improved, but we can still observe issues with some of the modelines exposed by the monitor over EDID:

- blinking

- dead monitor

- monitor reports no signal

- monitor is active but no picture

Other modelines work just fine.

Q1) Is the link training to blame for this? Do you have any idea as to why some modelines work just fine and other modelines are problematic?

We have been testing other monitors as well, some monitor work (although, with the same problems listed above), and other monitors won't work at all, like we get a dead monitor no matter what resolution we are trying to set. I wonder if the problem with monitors that don't work at all is the ASSR Display Authentication method? 

The software enables the ASSR Display Authentication method by means of register at DisplayPort address 0x0010A.
Looking at the DisplayPort specification for eDP_CONFIGURATION_SET (address 0x0010A), I read:
"For eDP Sinks:

Bit 0 = ALTERNATE_SCRAMBER_RESET_ENABLE
Source sets to 1 to select the alternate scrambler reset.
Writes ignored if ALTERNATE_SCRAMBLER_RESET_CAPABLE=0
Power-on default value = 0"

If I then read the description for eDP_CONFIGURATION_CAP from the DisplayPort specification (address 0x0000Dx) I find:
"Always reads 00h for external receivers. For embedded DisplayPort (eDP) receivers:

Bit 0 = ALTERNATE_SCRAMBLER_RESET_CAPABLE
A setting of 1 indicates that this is an eDP device that can use the eDP alternate
scrambler reset value of FFFEh."

Q2) My interpretation of this is that unless the monitor explicitly supports this, we will get no picture. Is that right? If my interpretation is wrong, what could be the cause for some monitors to not work at all with the SN65DSI86?
All of the monitors we have tested so far report ALTERNATE_SCRAMBLER_RESET_CAPABLE as 0, and yet some of them work(-ish), and others are completely dead.
Thanks,
Fab
  • 0
    TI__Guru*** 140115 points

    Fab

    1. Could you please disable ASSR and see if it will resolve some of the issue you are having?

    To disable ASSR

    • Pull TEST2 pin high 
    • ======ASSR RW control ======
    • <i2c_write addr=0x2D count=1 radix=16> FF 7 </i2c_write>/>
    • <i2c_write addr=0x2D count=1 radix=16> 16 1 </i2c_write>/>
    • <i2c_write addr=0x2D count=1 radix=16> FF 0 </i2c_write>/>
    • ===== Enhanced Frame, and Vstream Enable ======
    • <i2c_write addr=0x2D count=1 radix=16> 5A 0C </i2c_write>/>

    2. After ASSR has been disabled and monitors still not working, could you please dump out registers 0xF0 to 0xF8? Register 0xF8 in particular would indicate an issue with the link training. Sometimes errors flags at register 0xF0 to 0xF3 can be set at power-on or during start of the DSI stream. For this reason, it is recommended to clear flags by writing 0xFF and then reading back status flags.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 80 points

    Hi David,

    thank you for your reply.

    It's taking us a little bit of time to try and follow your suggestions because our design does not have support for pin TEST2, we have ordered (and now received) the demo board for the SN65DSI86, and we are trying to wire things up to another demo board to try and see if we can do what you are asking us to do.

    I'll be in touch as soon as we have some answers.

    Thanks,

    Fab