Re: Deprecate the ppc405 boards in QEMU?

From: BALATON Zoltan <balaton@eik.bme.hu>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
	"Thomas Huth" <thuth@redhat.com>,
	dbarboza@redhat.com, "QEMU Developers" <qemu-devel@nongnu.org>,
	"Wainer dos Santos Moschetta" <wainersm@redhat.com>,
	"Greg Kurz" <groug@kaod.org>, "Alexander Graf" <agraf@csgraf.de>,
	qemu-ppc <qemu-ppc@nongnu.org>, "Cédric Le Goater" <clg@kaod.org>,
	"Cleber Rosa" <crosa@redhat.com>,
	"Hervé Poussineau" <hpoussin@reactos.org>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>,
	"David Gibson" <david@gibson.dropbear.id.au>
Subject: Re: Deprecate the ppc405 boards in QEMU?
Date: Tue, 19 Oct 2021 16:56:58 +0200 (CEST)	[thread overview]
Message-ID: <6be2745-2eb7-7b85-31c3-def20eb21f@eik.bme.hu> (raw)
In-Reply-To: <5491ed41-7328-3949-12ad-1a94f0f525d1@csgroup.eu>

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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