Clara BW Fastboot / replace kernel with clara colour one possible

[matthiasmr]

Hey there,

I have a tolino shine 5 (same as kobo clara BW) and just played around with it. I came here to share my findings. They are valid from firmware 5+, but some parts seem to be there before already.

Beware: The following commands can brick your device _permanently_! Use at your own risk and own understanding. Also, you might accidentally hard reset your device deleting _all_ data!

Fastboot:
Device is fastboot enabled. Accessing is a little bit tricky:
* Turn device off and wait a moment to be sure it's off.
* Unplug the USB cable
* run your fastboot command like `fastboot oem readlkver` already, it will wait for the device
* Turn device on, keeping power button pressed
* very shortly after (within a few tenths of a sec) plug in the USB cable
* LEDS should flash very quickly.
* Keep power button pressed a bit longer, you'll see fastboot working. Feel free to release power button now.

To run a second fastboot command, unplug and replug USB cable. The device stays in fastboot mode.

With `fastboot reboot` you'll boot to bootloader which will overwrite system partition or maybe even hard reset your device!. To actually reboot, long-press the power button.

* `fastboot flash system_a path_to_img` flashes system
* `fastboot flash boot_a path_to_img` flashes kernel

You should not try to flash uboot or tee or bl2 - breaking any of those partitions renders fastboot unusable.

I went further and flashed the spa-colour kernel on my spa-bw device (via fastboot - so I knew if it flashed something I could revert by flashing the old one ).
Actually, flashing via fastboot is way quicker than using the update.tar method.

I compared the device trees of colour and bw before: They _seemed_ to be equivalent despite colour having a dual core, 2 GHz CPU (bw: single core, 1 GHz). I did not see that the touch screen controller is initialized with a different register setting - now my touch screen is inverted on the X-Axis and I didn't bother finding a way to reverse (I guess flashing back old kernel would work).

Unfortunately, my second CPU does not come up:

lscpu
Architecture:           armv7l
  Byte Order:           Little Endian
CPU(s):                 2
  On-line CPU(s) list:  0
  Off-line CPU(s) list: 1
Vendor ID:              ARM
  Model name:           Cortex-A53
    Model:              4
    Thread(s) per core: 1
    Core(s) per socket: 1
    Socket(s):          1
    Stepping:           r0p4
    CPU max MHz:        2000.0000
    CPU min MHz:        600.0000
    BogoMIPS:           15.60
    Flags:              half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm aes pmull sha1 sha2 crc32

Trying to put it online logs a kernel error message -22 (Invalid argument).

I have seen a `/proc/cpuinfo` dump of a dual core tolino vision colour which also only showed _one_ cpu core - I expect there could be a problem with the kernel that Kobo might not have noticed themselves

[matthiasmr]

I did a bit of research about the touch screen:
The difference is the CY_MT_FLAG_INV_Y Bit which invertes the Y axis before registering the touch, so it is a pure software thing, but unfortunately I cannot change this parameter after booting. So the only way to use this properly is to invert that again in KoReader or proxy the input device both seem a bit complicated...

[matthiasmr]

I could not withstand...

touch_mirrored_x = false;

in my device config in koreader frontend/device/kobo/device.lua ...

It was way to easy. Seems like I'll run with 2 GHz from now on until the next firmware update :-)

[matthiasmr]

I attached a boot log of my Kobo Clara BW bootet with the Kobo Clara Colour kernel. Maybe someone spots why the second CPU is not coming up?

[matthiasmr]

Okay, I just got confirmation that for Tolino vision color (=Kobo Libra Colour) it is the same - lscpu:

Architecture: armv7l
Byte Order: Little Endian
CPU(s): 2
On-line CPU(s) list: 0
Off-line CPU(s) list: 1
Vendor ID: ARM
Model name: Cortex-A53
Model: 4
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 1
Stepping: r0p4
CPU max MHz: 2000.0000
CPU min MHz: 600.0000
BogoMIPS: 52.00
Flags: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lp ae evtstrm aes pmull sha1 sha2 crc32

[matthiasmr]

Before any rumours are spread: Maybe I am wrong. On said vision colour the second core might have been turned off by koreader. I'll slow down here and verify again first. Sorry for the noise!

[DNSB]

Originally Posted by matthiasmr

I attached a boot log of my Kobo Clara BW bootet with the Kobo Clara Colour kernel. Maybe someone spots why the second CPU is not coming up?

If I remember correctly, the Clara BW has a MediaTek MT8113L single core ARM A53 1 GHz while the Clara Colour and Libra Colour have a MediaTek MT8113T dual-core ARM A53 2 GHz.

If this is correct, there is not second CPU on the Clara BW.

[matthiasmr]

While this could be true, I have following indicators to it not being true:
- bw & color have the exact same cpu core voltages for the frequencies they share - so the MT8113L is likely not another "lower power" process. So it is unlikely, that the cores are not similarly capable as the other one. I dod not see any stability problems in my tests so far, but I didn't try long.
- If you search the internet for MT8113L it likely doesn't exist
- Even if it exists, I can't believe it makes sense to save a few cents per piece and need a different stack of PCBs for that.

the ntx firmware file is different for bw & color - also there might be a hwconfig bit doing some initialisation that doesn't allow the second core to come up on my device.
Or you are just right and it doesn't exist

[matthiasmr]

So a last update on the CPU thingy:
First of all, the Tolino Vision Color / Kobo Libra Colour really has a dual core CPU. I am sorry for spreading the rumours of it not working, I was not aware that Koreader is actually shutting down the cores when idling.

I also compared the hwconfig between those and could not spot a relevant difference.

So:
* Either there is a difference in the NTX firmware binary disabling the second core on mine
* Or it _actually_ does not exist.

I stop here now. Still good to know it's possible to overclock to 2 GHz by replacing the kernel, as long as you accept the quirks with the touch screen inversion.

Some speed data: (start of display change/update finished, recorded at 30 fps)
2GHz:
Epub, Koreader,
Normal page flip: 4/9 frames, 6/11 frames 5/10 frames
going from cover page to next page: 6/11 frames
Going back to cover: 30/37 frames

1GHz:
Epub, Koreader, going from image page to next page: 7/13 frames
Going back to image: 26/31 frames
Normal page flip: 6/11 frames 5/10 frames

So... I am really curious why there was no actual speed improvement, honestly it even felt quicker with the fast CPU, but Koreader is really nice already.
Nickel @ 1 GHz, same epub:
page flip: 13/18 13/18 14/19
cover load: 22/30
cover leave: 14/19

Wow...

[de3sw2aq1]

Originally Posted by matthiasmr

Device is fastboot enabled. Accessing is a little bit tricky:

Thanks for this info about fastboot on the Clara BW.

I tried this out on my brand-new Clara BW hoping there would be a way to backup the flash partitions, but "fastboot fetch" is unimplemented and I don't know all the OEM commands. It looks like the Shine update files include a raw disk rootfs.img unlike Kobo's update tarballs? I guess I could dd the partitions over SSH and get an almost-perfect backup.

Where did you discover "fastboot oem readlkver", do you have a list of all OEM commands?

I was unable to access fastboot on Windows, I think I'm missing some drivers (I found some drivers I didn't try because they were unsigned). The Kobo appears briefly as USB VID 0e8d PID 201c when starting up while holding the power button and the LED blinks rapidly. I used Linux instead, and had no trouble with connecting to fastboot. After I ran one command, it stayed in fastboot mode until rebooting, I did not need to unplug and replug the USB cable to run additional commands.

The steps I used were basically:
1. Start with the USB cable disconnected from the device
2. Run "fastboot oem readlkver" on my Linux PC before connecting the device
3. Hold the device's power button and immediately connect the USB cable. The LED should blink rapidly and the fastboot command should succeed.
4. Release the power button
5. I could then run additional fastboot commands without unplugging