[Letux-kernel] [PATCH 00/20] A bunch of JZ4730 fixups for letux-kernel

[Lubomir Rintel]

Hello Nikolaus

(also, sorry for botching your name in the branch name in a recent
message. I was lazy to check and took chances)

On Wed, Dec 02, 2020 at 09:45:31PM +0100, H. Nikolaus Schaller wrote:
> Hi Lubomir,
> 
> > Am 30.11.2020 um 07:50 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> > 
> > Hi Lubomir,
> > 
> >> Am 28.11.2020 um 16:31 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> >>> 
> >>> Then I checked out your complete tree, copied the .config to the right location and:
> >>> 
> >>> 2919423 bytes read
> >>> ## Booting image at 80600000 ...
> >>> Image Name:   Linux-5.10.0-rc5-letux-l400+
> >>> Image Type:   MIPS Linux Kernel Image (gzip compressed)
> >>> Data Size:    2919359 Bytes =  2.8 MB
> >>> Load Address: 80100000
> >>> Entry Point:  8053d0f4
> >>> Verifying Checksum ... OK
> >>> Uncompressing Kernel Image ... OK
> >>> 
> >>> Starting kernel ...
> >>> 
> >>> [    0.000000] Linux version 5.10.0-rc5-letux-l400+ (hns at iMac.fritz.box) (mipsel-linux-gnu-gcc (GCC) 4.9.2, GNU ld (GNU Binutils) 2.25) #4026 PREEMPT Sat Nov 28 14:32:55 CET 2020
> >>> [    0.000000] CPU0 revision is: 02d0024f (Ingenic XBurst)
> >>> [    0.000000] MIPS: machine is letux400,minipc
> >>> [    0.000000] earlycon: jz4740_uart0 at MMIO32 0x10030000 (options '115200n8')
> >>> [    0.000000] printk: bootconsole [jz4740_uart0] enabled
> >>> [    0.000000] printk: debug: ignoring loglevel setting.
> >>> [    0.000000] User-defined physical RAM map overwrite
> >>> [    0.000000] Initrd not found or empty - disabling initrd
> >>> [    0.000000] cma: Reserved 32 MiB at 0x01000000
> >>> ...
> >>> 
> >>> So there is a subtle difference between your minimalistic tree and the full letux tree which blows up the uImage by ca. 80% and makes it fail to boot.
> >>> Have to study this now... But I think we are close.
> >> 
> >> Seems to be something incompatible in my defconfig.
> >> If I merge your tree into mine and use your defconfig it works.
> >> The one that is ok for CI20 (of course after switching to JZ4730) fails.
> >> 
> >> This is now a bisectable problem...
> > 
> > Yes, it was - partially - bisectable. But it is not a specific CONFIG.
> > And not a specific subsystem compiled into the kernel.
> > 
> > Rather it appears as if there is a limit of ca. 3800000 Bytes for the uImage Data Size.
> > Above that there is no sign of activity. Below the kernel boots.
> > 
> > I have cross-checked and the vmlinux.bin is quite exactly 8 MB in that cases which gets
> > compressed into these ca. 3800000 Bytes.
> > 
> > So please can you
> > a) check what happens for your build if you configure for bigger uImage (so that vmlinux.bin is more than 8MB)
> >   (e.g. CONFIG_INET, CONFIG_WIRELESS, CONFIG_POSIX_MQUEUE, CONFIG_CGROUPS, CONFIG_NAMESPACES, CONFIG_KEXEC, CONFIG_SUSPEND)
> >   until your kernel size goes beyond 3.8 MB resp. 8 MB?
> > b) try to boot my smaller uImage-good and the full uImage [1] and look by JTAG why the uncompression fails for the latter?
> >   (NOTE: it seems to be jz4730 specific since the CI20 has no problems with bigger uImages)
> > c) have ideas why the appended-DTB search algorithm fails? This would not be used for the CI20.
> 
> Have you had time to think about this finding?

Not until late last night; but then my IQ dropped to a level I was not
able to pen a reasonable reply :)

I was able to reproduce your issue. It seems to me that the factory
U-Boot generally limits the image to 8MB uncompressed, and your raw image
seems to be about 12 MB:

  common/cmd_bootm.c:#define CFG_BOOTM_LEN        0x800000        /* use 8MByte as default max gunzip size */

I can't see a workaround other than newer U-Boot. I've written down some
documentation about it:

  https://projects.goldelico.com/p/letux400/page/UpdateUboot/

If you don't have a JTAG setup and are not comfortable with the idea of
rewriting the booloader, plase let me know. The newer U-Boot can also be
turned into an uImage and chain-booted from the factory loader, but I'd
have to dig out my notes. I left my machine at the hackerspace yesterday
so I can't try it out at the moment.

Your kernel loaded fine, but I also left the dmesg on my hackerspace
machine. I guess I'll try to follow up with more useful response, also
addressing the TODOs in the wiki page linked above. But I guess this is
better than nothing.

Regards
Lubo

> 
> BR and thanks,
> Nikolaus
> 
> > 
> > BR and thanks,
> > Nikolaus
> > 
> > [1]: https://download.goldelico.com/letux-kernel/letux-5.10-rc5-l400/
> > _______________________________________________
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>