Cannot flash bootloader image.

[MaciejMalczyk]

I have problem with step 7 - nvflash downloads bootloader image to Nexus tablet but after reboot it does not boot into bootloader even with pwr + vol down. Instead it goes to APX mode. Device have broken system image and it will not boot automatically into system after bootloader flash. Is there any way overcome this? Or maybe i'm doing something wrong?

The only difference that i have in comparison to debrick instructions is flag: "sdram config strap: 1" from 6th step.

[tofurky]

have you tried appending --sync to the command in step 7?

[MaciejMalczyk]

Yes. Unfortunatelly it didn't help. Nvflash hangs at "bootloader/bootloader-grouper-4.23.img sent successfully" and after force reboot to bootloader mode device falls to APX.

[tofurky]

it shouldn't hang like that. uart would be useful to see what is going on there.

is this by any chance the 3g version (tilapia / nakasig) ? or is it the wifi (grouper / nakasi)?

[MaciejMalczyk]

This is for sure grouper. When the bootloader was working normally the codename grouper was on the screen. Tablet went to APX state after my trials to unlock bootlooder. Device had btoken system partition (but for 99% logicaly, not physicaly because i can tried emmc read test from other issue here but for morze than 2GB of disk space).
Maybe i should format partition where system is written and than try to flash bootlooder? Is it even possible to do with nvflash?

I will try to find out where is and how to connect to uart on this device (propably with PostmarketOS wiki). What i should expect on uart tty?

[tofurky]

i don't think that flashing system will prevent APX mode, system should only come into play after the kernel boots.

after step 6, you could try uploading zeroes to the LNX partition like shown in step 9 of the ouya debrick. maybe it's possible that it's hanging trying to boot the existing kernel on there, UART would show this definitively though.

truncate -s 8M LNX_all_zeroes.bin
sudo ./utils/nvflash_v1.13.87205_miniloader_patched --resume --download LNX LNX_all_zeroes.bin --go

in the ouya's case, it automatically falls back to standard fastboot mode at that point. i'm unsure how the n7 will behave there.

if you wind up in fastboot mode (dmesg -Tw will show this), you could then try running:

sudo fastboot flash bootloader bootloader/bootloader-grouper-4.23.img

if it didn't go to fastboot mode automatically, try step 7 again with --sync. note you should only need to overwrite the LNX (kernel) partition with zeroes once in order to see if step 7 stops hanging.

n7 uart isn't documented anywhere afaik, i found a schematic floating around the net for the ME370T (http://www.s-manuals.com/pdf/motherboard/asus/asus_me370t_r1.0_schematics.pdf) see:

https://github.com/tofurky/tegra30_debrick/blob/master/image/n7_uart.jpg
https://github.com/tofurky/tegra30_debrick/blob/master/image/n7_uart_schematic.jpg
https://github.com/tofurky/tegra30_debrick/blob/master/image/n7_uart_context.jpg

if you do try this, be careful though, the pads on the pcb are quite fragile and any amount of tugging on the soldered wires may just rip them clear off the board.

by default there is no uart output, using this patched bootloader will give output:
https://github.com/tofurky/tegra30_debrick/blob/master/bootloader/bootloader-grouper-4.23_uart.img

you shouldn't actually write bootloader-grouper-4.23_uart.img to the EBT partition, just use it for step 6 i.e.:

sudo ./utils/nvflash_v1.13.87205_miniloader_patched --setbct --bct ./bct/nexus_7_grouper_bct.bin --configfile ./utils/flash.cfg --bl ./bootloader/bootloader-grouper-4.23_uart.img --go

on the main README.md page there is UART output shown for the various steps.

it should give a hint as to why step 7 is hanging.

oh, and fastboot oem uart-on has basically the same effect as using the uart patched bootloader, but it is hard to run that if you don't have fastboot access :)

[MaciejMalczyk]

Thank you for your response. I tried flashing LNX and i was able to use fastboot. Unfortunately i cannot flash bootloader and system image - device hangs while tries to flash image on device. With my knowledge this looks like bad blocks in emmc.

[tofurky]

the original n7 i debricked apparently had bad blocks, too, but it seems they were maybe eventually remapped by the controller in the emmc flash chip. they did not prevent reflashing entirely, though.

[MaciejMalczyk]

Is there any point of writing with zeros bootloader partition and then trying to flash bootloader? I'm thinking of something simmilar to LNX flash with zeros.

[tofurky]

wouldn't hurt if it's already bricked, maybe it could trigger a bad block remap if you try enough times :) writing the LNX partition with zeroes is to trick the bootloader into entering 'fastboot' mode from its current 'Nv3p Server' (nvflash) mode.