TPS65982: MUX RFU Enable

Eric K

Part Number: TPS65982

Register 0x6E of the TPS65982 is the MUX Status (Debug) Register according to TI's TPS6598x Host Interface Tools software.

Bit 18 of this register is "MUX RFU Enable" which appears to describe whether or not the SBU crossbar multiplexer is enabled.

The issue we are having is that the "MUX RFU Enable" bit is correctly set to 1 when in debug accessory mode:

$ sudo i2ctransfer -f -y 0 w1@0x3f 0x69 r5
0x04 0x00 0x02 0x02 0x4a
$ sudo i2ctransfer -f -y 0 w1@0x3f 0x6e r9
0x08 0x00 0x00 0x1f 0x06 0x01 0x00 0x00 0x00

But it's not enabled when in TBT mode (notice 0x1b of the third byte in register 0x6e this time):

$ sudo i2ctransfer -f -y 0 w1@0x3f 0x59 r14
0x0d 0x03 0x0c 0x00 0x00 0x00 0x01 0x00 0x01 0x00 0x00 0x00 0x00 0x00
$ sudo i2ctransfer -f -y 0 w1@0x3f 0x6e r9
0x08 0x00 0x80 0x1b 0x47 0x01 0x00 0x00 0x00

Why isn't the "MUX RFU Enable" bit 1 in TBT mode (but it is in debug accessory mode)? How can I get it to be 1?

over 3 years ago

0 Christodulos Tsongas over 3 years ago

TI__Genius 12905 points

Eric,

Typically the SBU enables are done via GPIO Events (example AMSEL Event).

Where are you finding the information about the TPS65982 MUX Status register? I am looking at this one in the TPS65982 page:

https://www.ti.com/lit/pdf/slvuan1

There is not reference of MUX register I am able to find.

Thanks,

Chris

0 Eric K over 3 years ago in reply to Christodulos Tsongas

Prodigy 80 points

Hi Christodulos,

Register 0x6E, the MUX Status (Debug) Register, is not documented in the Technical Reference Manual. It is only documented in TI's TPS6598x Host Interface Tools software, here's what it looks like when in debug addessory mode (notice "MUX RFU Enable" is set here):

The SBU lines are multiplexed by the TPS65982, AMSEL is an output pin used for multiplexing the super speed lanes. This is not relevant.

Repeating the question:

Why isn't the "MUX RFU Enable" bit 1 in TBT mode (but it is in debug accessory mode)? How can I get it to be 1?

Best regards,

Eric

+1 Christodulos Tsongas over 3 years ago in reply to Eric K

TI__Genius 12905 points

In the Intel VID Config register, try setting Legace TBT Adapter to 0 (is not a Legacy Adapter) and let me know if that fixes this issue.

0 Eric K over 3 years ago in reply to Christodulos Tsongas

Prodigy 80 points

That seems to have done it:

$ sudo i2ctransfer -f -y 0 w10@0x3f 0x52 0x08 0x03 0x02 0x00 0x00 0x00 0x00 0x02 0x05
$ sudo i2ctransfer -f -y 0 w1@0x3f 0x6e r9
0x08 0x00 0x80 0x1f 0x47 0x01 0x00 0x00 0x00

Thank you Christodulos!

0 Christodulos Tsongas over 3 years ago in reply to Eric K

TI__Genius 12905 points

No problem!

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TPS65982: MUX RFU Enable