Re: Deprecate the ppc405 boards in QEMU?

[BALATON Zoltan]

On Tue, 19 Oct 2021, Christophe Leroy wrote:
> Le 19/10/2021 à 15:44, Christophe Leroy a écrit :
> > There is something:
> >
> > => bootm 0
> > Wrong Image Format for bootm command
> > ERROR: can't get kernel image!
> >
> > => md 0
> > 00000000: 00000000 b497aae1 616e9207 003227a4    '..V....an...2'.
> > 00000010: 00000000 00000000 ee36255f 05070201    .........6%_....
> > 00000020: 4c696e75 782d352e 31352e30 2d726335    Linux-5.15.0-rc5
> > 00000030: 2d303232 32342d67 61336330 30376164    -02224-ga3c007ad
> > 00000040: 1f8b0800 00000000 0203ec5c 0f7013e7    ...........\.p..
> >
> > => mw.l 0 0x27051956
> >
> > => bootm 0
> > ## Booting kernel from Legacy Image at 00000000 ...
> >     Image Name:   Linux-5.15.0-rc5-02224-ga3c007ad
> >     Image Type:   PowerPC Linux Kernel Image (gzip compressed)
> >     Data Size:    3286948 Bytes = 3.1 MiB
> >     Load Address: 00000000
> >     Entry Point:  00000000
> >     Verifying Checksum ... Bad Data CRC
> > ERROR: can't get kernel image!
> >
> >
> > So we have something but it seems it gets overwritten by stuff.
> >
> > Anyway loading a uImage at 0 is just bad because it is a gzipped image that 
> > should get gunzipped at address 0.
> >
> > Or should we just copy the raw kernel at 0 and jump to the entry point ? 
> > But then we also need a device tree somewhere.
>
> If I change KERNEL_LOAD_ADDR to 0x1000000, I can bootm at that address, and 
> it seems it properly decompress the kernel:
>
> => bootm 0x1000000
> ## Booting kernel from Legacy Image at 01000000 ...
>   Image Name:   Linux-5.15.0-rc5-02224-ga3c007ad
>   Image Type:   PowerPC Linux Kernel Image (gzip compressed)
>   Data Size:    3296789 Bytes = 3.1 MiB
>   Load Address: 00000000
>   Entry Point:  00000000
>   Verifying Checksum ... OK
>   Uncompressing Kernel Image ... OK
>
>
> And it initialises the MMU properly.
>
> Then it gets stuck because there is no devicetree.
>
> (gdb) bt
> #0  0xc00094cc in udelay ()
> #1  0xc0025d34 in panic ()
> #2  0xc06415a0 in early_init_devtree ()
> #3  0xc0641da8 in machine_init ()
> #4  0xc0002200 in start_here ()

Maybe you need to embed a dtb in your kernel if that's possible somehow? 
Or QEMU has a -dtb option that sets machine->dtb but you need board code 
to do something with it. See how it's done in other boards like 
virtex_ml507 and sam460ex. But maybe you'd be better off not using -kernel 
option as it seems to not really working for these 405 boards but load and 
start the kernel from u-boot. Not sure what device does u-boot support but 
QEMU can emulate usb-storage, network, different disks so something might 
work with u-boot if this board has any peripherals. If it doesn't emulate 
any peripherals what do you expect to do with the kernel once it boots?

Regards,
BALATON Zoltan