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How to free up emmc pin (8.24) for GPIO? #225

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mfallavol opened this issue Jan 24, 2022 · 3 comments
Open

How to free up emmc pin (8.24) for GPIO? #225

mfallavol opened this issue Jan 24, 2022 · 3 comments

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@mfallavol
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I need to use P8.24 for GPIO. The default mode for this pin is 31h (mmc1_dat1)

I've modified uEnv.txt to disable eemc: disable_uboot_overlay_emmc=1
and I see the appropriate message on boot:
uboot_overlays: uboot loading of [/lib/firmware/BB-BONE-eMMC1-01-00A0.dtbo] disa bled by /boot/uEnv.txt [disable_uboot_overlay_emmc=1]...

My overlay attempts to free up the pin with:
P8_24_pinmux { status = "disabled"; };
but I'm wondering if that is the correct way to do it for an emmc pin because I do the same thing with all of my other GPIOs and they change modes appropriately but P8.24 is still 31h and I can't take control of it. show-pins shows:
P8.24 / eMMC d1 1 fast rx up 1 mmc 1 d1
where-as my other GPIO outputs show up like this:

P9.23                             17 fast rx down 7 gpio 1.17 lo >>  P9_23
P9.25 / audio osc                107 fast rx down 7 gpio 3.21 hi >>  P9_25

Is there something I'm missing?

@RobertCNelson
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That's the correct way... but note, not every "eMMC" can be disabled... Using the eMMC pins should be considered a last resort..

Regards,

@mfallavol
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Thanks @RobertCNelson but is there a reason this would have changed with the 4.x kernel and UBOOT overlays vs the 3.8 kernel? This same BBB with 3.8.13 works. (With a different overlay of course.)

@RobertCNelson
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Nope, if it worked before, i'd expect it to work now (with the exact same hardware)... I forget which model of eMMC on some boards can't be disabled..

Regards,

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