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Last Post 08 Aug 2017 02:58 PM by  Alex Roberts
PMIC RTC Security
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Alex Roberts
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08 Aug 2017 02:46 PM

    Looking at the schematics, MSecure signal on the TPS65950 PMIC is tied high to 1.8V (VIO_1V8). I am assuming this puts the PMIC in secure, preventing my ability write to the real-time clock registers via I2C.

    A quick test in LOSH shows writing the year, for example, does not update the register value. From the TPS65950 TRM,  YEARS_REG is in the 0x4B group and the physical address is 0x21

    losh> x /b 0x004B0021 1 /dev/pm0

    0x004B0021 00

    losh> w /b 0x004B0021 0x17 /dev/pm0

    losh> x /b 0x004B0021 1 /dev/pm0

    0x004B0021 00

    Any thoughts?

     

     
    Alex Roberts
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    Posts:4


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    08 Aug 2017 02:58 PM
    Looks like I can answer my own question. The PMIC does not appear to be in secure mode; I have to write the GET_TIME bit of the RTC_CTRL_REG to latch the current time values before I can read them.

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