On Wed, Jul 12, 2017 at 2:29 PM, Kenny Koller
<[email protected]> wrote:
> Can someone help me understand the output of U-Boot? Please see my questions
> inline in green below. Also is there a sort Theory of Ops for U-Boot? I
> found a User Manual at the DENX site but nothing about the details of the
> boot sequence and how/where it searches for things. Thanks.

best details:

https://lists.denx.de/listinfo/u-boot

> U-Boot SPL 2017.01 (Jun 28 2017 - 23:47:37)
> Trying to boot from MMC1MMC partition switch failed
>
>
> I know what a partition is. What is a partition switch?
>
> *** Warning - MMC partition switch failed, using default environment
>
> Was it trying to read the environment from a partition or boot? We haven't
> launched U-Boot yet so what environment is this? Loaded to memory? Where?
>
>
> reading u-boot.img
> reading u-boot.img
>
>
> Why is U-Boot being read twice?

it tried to raw read u-boot.img but switch to the 1st partition in the
second read.

>
>
>
> U-Boot 2017.01 (Jun 28 2017 - 23:47:37 +0000)
> CPU  : AM335X-GP rev 2.1
> I2C:   ready
> DRAM:  512 MiB
> MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
> ** First descriptor is NOT a primary desc on 1:1 **
>
>
> Does this mean a bootable partition? Looks to be MMC 1 partition 1 which
> would be true as I erased it. Why is it so upset about this? It's no unheard
> of to boot from an SD card (and lots of other methods).
>
>
> *** Warning - bad CRC, using default environment
>
>
> Found the answer to this on the DENX site: It's trying to read an
> environment from uninitialized flash.
>
>
> <ethaddr> not set. Validating first E-fuse MAC
> Net:   cpsw, usb_ether
> Press SPACE to abort autoboot in 2 seconds
> switch to partitions #0, OK
>
>
> Partitions are referred to as 1-4 (at least with MBR). What is zero?
>
>
> mmc0 is current device
> SD/MMC found on device 0
> reading boot.scr
> ** Unable to read file boot.scr **
> reading uEnv.txt
> 411 bytes read in 3 ms (133.8 KiB/s)
> Loaded env from uEnv.txt
>
>
> I do have a uEnv.txt on a partition 1 (FAT) of MMC0 (SD card). I've added an
> echo statement but I'm not seeing anything from it. Should I? I was
> expecting it to execute it like script in the hush shell. Maybe it only
> assigns variables? With the above it looks to be using MMC0 (SD card). Does
> it only look at the bootable partition (FAT in my case) or will it also
> attempt to find this file elsewhere?

the function called is:

env import -t -r $loadaddr $filesize

nothing get's echoed..

>
> Importing environment from mmc0 ...
> switch to partitions #0, OK
> mmc0 is current device
> Scanning mmc 0:1...
> switch to partitions #0, OK
> mmc0 is current device
> SD/MMC found on device 0
> 5655304 bytes read in 389 ms (13.9 MiB/s)
> 34643 bytes read in 43 ms (786.1 KiB/s)I## Flattened Device Tree blob at
> 88000000
>
>   Booting using the fdt blob at 0x88000000
>   Loading Device Tree to 8fff4000, end 8ffff752 ... OK
>
>
> What is going on here? The DT was at 8800.0000 is it being moved?

u-boot's relocating things..

raw mode is much cleaner:

https://gist.github.com/RobertCNelson/a61e391168cdd4485a641097cc780aec

Regards,

-- 
Robert Nelson
https://rcn-ee.com/

-- 
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