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Is power enable GPIO required for pcie?

Question asked by Robin Findley on Sep 17, 2014
Latest reply on Sep 17, 2014 by Robin Findley

On my SabreSD (quad) board, I plugged in a RealTek-based mini-PCIe ethernet card (StarTech ST1000SMPEX).  The card is detected fine in u-boot.

On my TechNexion board, I plugged in the same card, but the card is not detected (same version of u-boot, 2014.07).

 

I compared the two dev boards, and corresponding software, I discovered one main difference:  The SabreSD board has a Power-Enable GPIO that controls a load-switch to the mini-PCIe slot.  The TechNexion doesn't have it.  So, I tried disabling the GPIO on the SabreSD board to see if that was the problem.  Sure enough, u-boot failed to detect the card.

 

In my understanding, PCIe should be able to work just fine without that GPIO, since it is really just intended for hot-plug capability.  Is that not true?  We have a custom board that doesn't have a power-enable, and I can't communicate over PCIe.

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