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am335x Reset pin configuration for eMMC

Ankur Tank
Expert 2985 points

We are using Beaglbone black based custom board. We have interfaced the eMMC with am335x.

We referred the device tree configuration for eMMC from below link,

github.com/.../am335x-bone-common-pinmux.dtsi

emmc_pins: pinmux_emmc_pins {
pinctrl-single,pins = <
0x80 (PIN_INPUT_PULLUP | MUX_MODE2) /* gpmc_csn1.mmc1_clk */
0x84 (PIN_INPUT_PULLUP | MUX_MODE2) /* gpmc_csn2.mmc1_cmd */
0x00 (PIN_INPUT_PULLUP | MUX_MODE1) /* gpmc_ad0.mmc1_dat0 */
0x04 (PIN_INPUT_PULLUP | MUX_MODE1) /* gpmc_ad1.mmc1_dat1 */
0x08 (PIN_INPUT_PULLUP | MUX_MODE1) /* gpmc_ad2.mmc1_dat2 */
0x0c (PIN_INPUT_PULLUP | MUX_MODE1) /* gpmc_ad3.mmc1_dat3 */
0x10 (PIN_INPUT_PULLUP | MUX_MODE1) /* gpmc_ad4.mmc1_dat4 */
0x14 (PIN_INPUT_PULLUP | MUX_MODE1) /* gpmc_ad5.mmc1_dat5 */
0x18 (PIN_INPUT_PULLUP | MUX_MODE1) /* gpmc_ad6.mmc1_dat6 */
0x1c (PIN_INPUT_PULLUP | MUX_MODE1) /* gpmc_ad7.mmc1_dat7 */
>;
};

Now my question why reset pin of eMMC is not configured ?

Thank you,

Regards,
Ankur
  • 0
    TI__Guru** 116100 points
    Hi,
    Have you checked the Beagle Bone schematics ?
    Whether the eMMC RESET pin has been connected/used ?
    Is there any GPIO used for reset ?
  • 0
    Expert 1185 points

    Hi Ankur,

    can you, please, specify what do you mean "reset pin"? If you mean power supply control pin, it is implemented only for mmc/sd 0 interface. For mmc/sd 1, 2 interfaces it is not available.
    Please refer to "18.2.1 MMC/SD/SDIO Functional Modes" in AM335x TRM.
    http://www.ti.com/lit/ug/spruh73l/spruh73l.pdf


    BR,
    Georgi

  • 0 in reply to Georgi Karpov
    Expert 2985 points

    Hi Titus/Georgi,

    Sorry for late reply,
    By reset pin I mean reset pin available on the eMMC, if you see below schematic(page 8) of Beaglebone Black you will see eMMC_RST pin which is connected to GPIO1_20
    Schematic:
    github.com/.../BBB_SCH.pdf
    But if you see the below dts file you won't see the configuration for eMMC_RST pin.
    am335x-bone-common.dtsi:
    github.com/.../am335x-bone-common.dtsi

    May be eMMC RST pin is not used in the normal scenario.
    Without this configuring eMMC RST pin also it works fine but still I was wondering if we need or not.

    Moreover eMMC datasheet describes following, I think by default Reset functionality is also not enabled in the eMMC.

    RST_n-Input-Reset:
    The RST_n signal is used by the host for resetting the device, moving the device to the preidle state. By default, the RST_n signal is temporarily disabled in the device. The host must set ECSDregister byte 162, bits[1:0] to 0x1 to enable this functionality before the host can use it.

    Thank you,

    Regards,
    Ankur