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AM62A7: Software reboot not working in eMMC boot mode

Vinay S
Intellectual 365 points
Part Number: AM62A7

We are using custom board based on AM62A7 CPU with emmc boot mode(0x1001) for booting

When board is powered on board boots properly from emmc but when we do a warm reset in Uboot/ kernel

board hangs and doesnot reboot

We referred below link and programmed eMMC HW reset enable OTP in 1 board and checked SW reboot worked

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1168342/faq-am62x-how-to-check-and-configure-emmc-flash-rst_n-signal-to-support-warm_reset-from-emmc-booting-on-am62x-sk-e2

Also we tested other boot modes in our board like USB host, USB DFU, eMMC UDA File system mode, In other boot modes board is rebooting properly during SW reboot.

we wanted to know why programming this OTP is required for SW reboot in emmc boot mode?

  • 0
    TI__Mastermind 23405 points

    Hi Vinay,

    I have assigned your query to our expert. As he is currently on a customer visit, the response would be delayed.

    Best Regards,

    Suren

  • 0 in reply to Suren Porwar
    TI__Guru 65135 points

    Hello Vinay,
    Please refer to eMMC device specification as quoted below
    e2e.ti.com/.../4395412
    >>>>
    Micron eMMC datasheet [https://www.mouser.com/datasheet/2/671/micron_technology_mict-s-a0006806196-1-1759129.pdf]
    • RST_n: The RST_n signal is used by the host for resetting the device, moving the device to the pre-idle state.
    • By default, the RST_n signal is temporarily disabled in the device.
    • The host must set ECSD register byte 162, bits[1:0] to 0x1 to enable this functionality before the host can use it.
    <<<<
    Best,
    -Hong

  • 0 in reply to Hong Guan64
    Intellectual 365 points

    Hi,

    If RST_n signal is required then our doubt is why SW reset is working when testing with eMMC UDA file system mode.

    and issue is seen only in eMMC boot mode.

  • 0 in reply to Vinay S
    TI__Guru 65135 points

    Hello Vinay,
    From eMMC spec, "The RST_n signal is used by the host for resetting the device."
    My understanding this would apply to booting from eMMC boot partition as well as UDA.
    Best,
    -Hong

  • 0 in reply to Hong Guan64
    Intellectual 365 points

    Hi Hong,

    Currently if EMMC HW reset enable is not programmed we are facing below issues in eMMC boot

    1. SW reboot is not working

    2. after pressing HW reset button board hangs and does not reboot

    We dont want to program the ECSD register byte 162 in eMMC since it is OTP.

    Is there any other way/workaround to resolve the above mentioned issues?

  • 0 in reply to Vinay S
    TI__Guru 65135 points
    Hong Guan64 said:
    • By default, the RST_n signal is temporarily disabled in the device.
    • The host must set ECSD register byte 162, bits[1:0] to 0x1 to enable this functionality before the host can use it.

    Once ECSD register byte 162 is set, on AM62A-SK, eMMC boot works as expected from either pressing HW RESET button or issuing SW WarmReset, for example, via "reset" from u-boot or "reboot" from kernel.

    Best,
    -Hong