ADV7625 HDCP Authentication  without a 5V signal

ADV7625/26/27 HDMI Receiver Authentication without 5V signal

►Attempting to authenticate (ADV7625/26/27 Rx) when no 5V signal is present causes the HDCP key controller to get stuck

  • HDCP cipher will not calculate R0’ (R0’ remains at all zeros)

►Once this occurs, HDCP key controller must be reset

  • Main I2C reset (IO Map, 0xFF[7]
  • Power-on reset

Workaround and Detection

►Workaround

  • Isolate the ADV762x from the HDCP activity on the DDC bus until a stable 5V signal is detected
  • Initialise HDMI Rx Repeater Map 0x7B[0] to 1
  • When cable_det_x_raw
  • When cable_det_x_rawfor the active port, set HDMI Rx Repeater Map 0x7B[0] to 1

►Detection

  • To detect this, the following algorithm is suggested
  • Use AKSV_UPDATE_RX1 / AKSV_UPDATE_RX2 and HDMI_ENCRPT_RX1 / HDMI_ENCRPT_RX2 interrupts to detect if the lock state has occurred
  • In normal operation both the AKSV_UPDATE and HDMI_ENCRPT interrupts trigger when authentication is successfully completed
  • If 3 x AKSV_UPDATE interrupts occur without a corresponding HDMI ENCRPT interrupt, this suggests the HDCP Key Controller needs to be reset

Code changes for the workaround

►Code changes

  • Whenever there is a no TMDS, the DDC port is disabled to avoid the HDCP controller lock state.
  • When we receive the XREP_EVENT_RX_TMDS_DETECTED in app_notify.cADIAPI_RxHdmiEnDdc() needs to be called to handle the DDC port.

►app_notify.c

Header 1 Header 2
Before Fix After Fix

case XREP_EVENT_RX_TMDS_DETECTED:

            ADIAPI_XRepRxGetSelectedPort(&SelPort);

            if (SelPort == *(RX_HDMI_PORT *)Buff)

            {

                ProcessFreeRun();

            }

            break;

case XREP_EVENT_RX_TMDS_DETECTED:

            ADIAPI_XRepRxGetSelectedPort(&SelPort);

            if (SelPort == *(RX_HDMI_PORT *)Buff)

            {

                ProcessFreeRun();

                if(EventInfo == 0)

                {

                    ADIAPI_RxHdmiEnDdc(FALSE);                    

                }

                else

                {

                    ADIAPI_RxHdmiEnDdc(TRUE);

                }

            }

            break;

►rx_hdmi.c

  • Include the below API for enable/disable the DDC.

                  ATV_ERR ADIAPI_RxHdmiEnDdc(BOOL Enable)

                  {

                     #if((RX_DEVICE ==7625)||(RX_DEVICE ==7626)||(RX_DEVICE ==7627))  

      return(HAL_RxHdmiEnDdc(Enable));

#else

      return (ATVERR_NOT_AVAILABLE);

#endif

         }

►rx_6g_hal.c

  • Include the below HAL API for enable/disable the DDC.

ATV_ERR HAL_RxHdmiEnDdc(BOOL Enable)

{

    if(!Enable)

    {

        HAL_I2CWriteByte(VRX_REPEATER_MAP_ADDR, 0x7b, 0x01);  

    }

    else

    {

        HAL_I2CWriteByte(VRX_REPEATER_MAP_ADDR, 0x7b, 0x00);  

    }

    return (ATVERR_OK);

}

►7625_ini_hal.c , 7626_ini_hal.c & 7627_ini_hal.c

  • HAL_RxInitHAL_RxHdmiEnDdc(FALSE);