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Device Tree changes to re-purpose MMC0

Michael Pergola
Intellectual 445 points
Other Parts Discussed in Thread: WL1835MOD, TPS65910

All,

We are debugging a Beaglebone Black-based custom design which uses MMC1 for eMMC and are trying to re-purpose MMC0 for WiFi. Cannot find how MMC0 pins are addressed in the device tree files (am33xx.dtsi, am335x-bone-common.dtsi or am335x-bone-common-no-capemgr.dtsi).

Has anyone used MMC0 for something other than uSD card device?

Regards,

   Michael

  • 0
    TI__Guru**** 170625 points
    Amit,

    Why you move AM335x post in DM814x forum?

    Michael,

    The right place for your question is Sitara forum:

    e2e.ti.com/.../791

    BR
    Pavel
  • 0 in reply to Pavel Botev
    Intellectual 445 points

    TI,

    Although I appreciate moving my post around, what  I would really appreciate would be an answer to the question. Is MMC0 dedicated by the Sitara AM335x processor as memory and cannot be utilized for another purpose (such as WL1835MOD)? If so, where in the TRM is this specified? I am using the Debian Jessie image on the custom BBB-like board.

    Also, I noticed that in the AM33xx.dtsi file there are definitions for MMC1, MMC2 & MMC3 but none for MMC0. Furthermore, the address for MMC1 is set in the dtsi file as mmc@48060000 but perusing the board's directory structure reveals:

    root@arm:~# ls -pal /sys/devices/platform/ocp/48060000.mmc/mmc_host/mmc0/

    total 0

    drwxr-xr-x 4 root root    0 Jun  9 13:38 ./

    drwxr-xr-x 3 root root    0 Jun  9 13:39 ../

    lrwxrwxrwx 1 root root    0 Jun  9 13:37 device -> ../../../48060000.mmc

    drwxr-xr-x 5 root root    0 Jun  9 13:38 mmc0:0001/

    drwxr-xr-x 2 root root    0 Jun  9 13:37 power/

    lrwxrwxrwx 1 root root    0 Jun  9 13:36 subsystem -> ../../../../../../class/mmc_host

    -rw-r--r-- 1 root root 4096 Jan  1  1970 uevent

    This is showing the address, 048060000, is associated with MMC0. This is highly confusing; do you have an explanation for this behavior?

    Michael

  • 0 in reply to Michael Pergola
    TI__Guru*** 125430 points
    The hardware documentation numbers from 0 but the dtsi numbers from 1. I also find it confusing but unfortunately it would be very disruptive to fix it because it would break everyone's code!

    I see no issue with using MMC0 for SDIO.
  • 0 in reply to Brad Griffis
    Intellectual 445 points

    OK, so I was able to get the WL1835MOD to come up using the MMC0 interface by altering the DTS/DTSI files attached.

    Please note that this is a custom board so we are not using UART4 nor eth0 and are using the TPS65910 PMIC in the design

    MMC0-WL1835MOD-DTS.zip

    The main thing to realize is, as Brad stated, in the DTS/DTSI files there are MMC1, MMC2 & MMC3 but the actual hardware linux directories on the board uses MMC0, MMC1 & MMC2. A better explanation in the device tree files would be extremely helpful!