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TPS65982: TPS65982: tps65982: hpd status and attention message

user6310225
Intellectual 320 points
Part Number: TPS65982

Related to https://e2e.ti.com/support/interface/f/138/t/923688

Our device with tps65982 is configured as a dp-alt-mode source (DFP_D) on a dual role port (usually acting as a power sink to get charged). When plugging an of the shelf USB-C to HDMI adapter  into our device the tps65982 in our device negotiates DP alt mode successfully (verified by data status register 0x5f) and DP sid status (0x58) however DPStatusRX in 0x58 never changes the HPD state (Bit 7) also GPIO4 is never asserted. I have no PD analyzer at hand so here's what i figured out by looking at registers when I2C_IRQ1 triggers (i've enabled all bits in that register):

0.) I'm seeing data status and status changes

1.) I'm seeing DRSwapComplete

2.) I'm seeing DiscoverModesComplete and VDMReceived with 2 VDOs: (0xff018043, 0x00000c05)

3.) I'm seeing VDMReceived with 1 VDO: 0xff018151

If I read that correctly step 2.) is the responders ack of the our DFP_D's discover modes. It offers one possible mode with usable pin assignment C and D. and step 3.) is the ack of the configure selecting that mode.

This matches Step 12 of the `USB PD and VESA DP Alternate Mode Flow` in your `PD Alternate Mode: DisplayPort` document. However it seems `Step 13` (self-initiated Attention message) never happens.


Can you please help with these two points:


1.) Would the UFP_D's attention message also trigger an IRQ with VDMReceived?

2.) Can you point to possible error sources why UFP_D would not send the attention message (and hence our DFP_D would not start sending DP data)?


Happy to provide configuration and schematics if that helps. Let me know where to send them.

  • 0
    TI__Genius 12700 points

    Hello,

    An expert from our team will get back to you shortly.

    Thank you,

    Hari

  • 0 in reply to Hari Patel1
    TI__Mastermind 28840 points

    Hello,

    Find answers to your two questions below

    1. Would the UFP_D's attention message also trigger an IRQ with VDMReceived?

    • Yes, once the UFP sends an attention message indicting that HPD has been set hi, the TPS65982 will trigger an IRQ event for the VDMReceived

    2. Can you point to possible error sources why UFP_D would not send the attention message (and hence our DFP_D would not start sending DP data)?

    • My next recommendation would be to get a PD controller and read the messages sent between the two devices to make sure everything looks correct from a messaging perspective. I think you have done a creative job reading our registers to interpret what is occurring on the CC messaging, but having a PD analyzer would definitively tell you whether or not the UFP is setting the HPD bit high or not and is following the DP alt mode correctly