[U-Boot] RFC, am335x_evm.h patch for u-boot on SD and rest on eMMC on BBB

[Robert P. J. Day]

 soldiering on with my configuring and building u-boot for my BBB, i
have a proposal for include/configs/am335x_evm.h:

#define CONFIG_BOOTCOMMAND \
        "run findfdt; " \
        "run mmcboot;" \
        "setenv mmcdev 1; " \
        "setenv bootpart 1:2; " \
        "setenv mmcroot /dev/mmcblk1p2 ro; " \    <-- add this line
        "run mmcboot;" \
        "run nandboot;"

the rationale is for when there is a full, bootable OS in eMMC on the
BBB, but someone wants to experiment with newer u-boot MLO and
u-boot.img files.

 as you can see, there is an early attempt to run mmcboot off of SD
card and, if that fails, the env vars are tweaked to now point to eMMC
as plan B:

        "setenv mmcdev 1; " \
        "setenv bootpart 1:2; " \

but if "mmcroot" isn't similariy tweaked, the boot process will still
try to mount the second partition on the SD card as the root
filesystem, which makes little sense.

 i realize you can use uEnv.txt to fix this, but it seems that the
*default* should be that, if you're switching to eMMC for the boot
partition, it only makes to switch to the same device for the root
filesystem.

 thoughts?

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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