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[FAQ] PROCESSOR-SDK-J721E: Changes required for interfacing eDP output with external serializer

Part Number: PROCESSOR-SDK-J721E

This article explains changes required in the PSDKRA driver for interfacing eDP output to external serializer.

  • There is a deglitch filter on the AUX receiver, which is used to suppress high frequency AUX output pulse. This filter requires to be disabled when interfacing eDP output with the serializer, because AUX communication might get suppressed due to this filter and AUX data may not be detected correctly by the AUX received and so DP training can potentially fail or it can cause hang or crash.

    In order to fix this issue, please below change. This change is described for the eDP driver in the PSDK RTOS 8.6 release. But it can be also applied to the other PSDK RTOS releases. 

    - In the API DP_SD0801_ConfigurePhyAuxCtrl, in the file ti-processor-sdk-rtos-j721e-evm-08_06_00_12/pdk_jacinto_08_06_00_31/packages/ti/drv/dss/src/csl/dp_sd0801/src/specific/dp_sd0801_spec.c, change the value of AUX_CONFIG_p register as shown below.

    uint32_t DP_SD0801_ConfigurePhyAuxCtrl(const DP_SD0801_PrivateData* pD)
    uint32_t retVal = CDN_EOK;
    uint32_t AUX_CONFIG_p;

    retVal = DP_SD0801_ConfigurePhyAuxCtrSF(pD);

    if (CDN_EOK == retVal)
    CPS_REG_WRITE(&pD->regBaseDp->dp_regs.AUX_CTRL_p, 0x0003);

    AUX_CONFIG_p = CPS_REG_READ(&pD->regBaseDp->dp_regs.AUX_CONFIG_p);

    AUX_CONFIG_p = 0x1F1301;

    CPS_REG_WRITE(&pD->regBaseDp->dp_regs.AUX_CONFIG_p, AUX_CONFIG_p);

    return retVal;