U-Boot DM device tree and Linux device tree - what are the differences and why?

[Rudolf J Streif <rudolf.streif@ibeeto.com>]

I have a custom board that is similar to the i.MX6UL 14x14. One
difference is that it has an eMMC rather than a SD card. Most recently I
upgraded from u-boot 2019.07 to u-boot 2020.01 and now u-boot cannot
detect the eMMC anymore.

For the 2019.07 version I did use CONFIG_FSL_ESDHC=y without
CONFIG_DM_MMC. That does not work anymore. Compilation fails with
"CONFIG_SYS_FSL_ESDHC_ADDR undefined". What has changed here and why?

Then I tried using CONFIG_FSL_USDHC=y and CONFIG_DM_MMC=y. I simply used
the device tree from the Linux kernel which works just fine for the
kernel. But it does not work for u-boot. It's hard to understand why.
Why would the u-boot device tree be different than the kernel device
tree? If that is even the issue.

It's an eMMC with 8-bit bus. Here are the definitions that work
perfectly well for the Linux kernel:

&usdhc2 {
??? pinctrl-names = "default";
??? pinctrl-0 = <&pinctrl_usdhc2>;
??? bus-width = <8>;
??? max-frequency = <200000000>;
??? vmmc-supply = <&sw2_reg>;
??? mmc-ddr-1_8v;
??? cap-mmc-highspeed;
??? non-removable;
??? keep-power-in-suspend;
??? status = "okay";
};

??? ??? pinctrl_usdhc2: usdhc2grp {
??? ??? ??? fsl,pins = <
??? ??? ??? ??? MX6UL_PAD_NAND_RE_B__USDHC2_CLK??? ??? 0x1b0d9 /*
eMMC_CLK */
??? ??? ??? ??? MX6UL_PAD_NAND_WE_B__USDHC2_CMD??? ??? 0x1b0d9 /*
eMMC_CMD */
??? ??? ??? ??? MX6UL_PAD_NAND_ALE__USDHC2_RESET_B??? 0x1b0d9 /* eMMC_RST */
??? ??? ??? ??? MX6UL_PAD_NAND_DATA00__USDHC2_DATA0??? 0x1b0d9 /*
eMMC_DAT0 */
??? ??? ??? ??? MX6UL_PAD_NAND_DATA01__USDHC2_DATA1??? 0x1b0d9 /*
eMMC_DAT1 */
??? ??? ??? ??? MX6UL_PAD_NAND_DATA02__USDHC2_DATA2??? 0x1b0d9 /*
eMMC_DAT2 */
??? ??? ??? ??? MX6UL_PAD_NAND_DATA03__USDHC2_DATA3??? 0x1b0d9 /*
eMMC_DAT3 */
??? ??? ??? ??? MX6UL_PAD_NAND_DATA04__USDHC2_DATA4??? 0x1b0d9 /*
eMMC_DAT4 */
??? ??? ??? ??? MX6UL_PAD_NAND_DATA05__USDHC2_DATA5??? 0x1b0d9 /*
eMMC_DAT5 */
??? ??? ??? ??? MX6UL_PAD_NAND_DATA06__USDHC2_DATA6??? 0x1b0d9 /*
eMMC_DAT6 */
??? ??? ??? ??? MX6UL_PAD_NAND_DATA07__USDHC2_DATA7??? 0x1b0d9 /*
eMMC_DAT7 */
??? ??? ??? >;
??? ??? };

Every time the eMMC is probed e.g 'mmc dev 1' it takes about a second
and then the response is 'MMC: no card present'.

I appreciate the help.

Thank you,
Rudi

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