Re: [Qemu-devel] [Qemu-ppc] [PATCH v3 03/10] raven: move BIOS loading from board code to PCI host

[Alexander Graf]

On 24.12.2013, at 03:02, Andreas Färber <address@hidden> wrote:

> Am 24.12.2013 01:32, schrieb Alexander Graf:
>> 
>> On 23.12.2013, at 22:54, Hervé Poussineau <address@hidden> wrote:
>> 
>>> Andreas Färber a écrit :
>>>> Am 23.12.2013 19:13, schrieb Hervé Poussineau:
>>>>> Alexander Graf a écrit :
>>>>>> On 23.12.2013, at 07:48, Hervé Poussineau <address@hidden> wrote:
>>>>>> 
>>>>>>> Hi,
>>>>>>> 
>>>>>>> Andreas Färber a écrit :
>>>>>>>> Hi,
>>>>>>>> Am 05.11.2013 00:09, schrieb Hervé Poussineau:
>>>>>>>>> Raven datasheet explains where firmware lives in system memory, so do
>>>>>>>>> it there instead of in board code. Other boards using the same PCI
>>>>>>>>> host will not have to copy the firmware loading code.
>>>>>>>> This part we had discussed and no one objected to the approach, so OK.
>>>>>>>>> However, add a specific hack for Open Hack'Ware, which provides only
>>>>>>>>> a 512KB blob to be loaded at 0xfff00000, but expects valid code at
>>>>>>>>> 0xfffffffc (specific Open Hack'Ware reset instruction pointer).
>>>>>>>> Was this part explained before? I don't spot the equivalent in the
>>>>>>>> deleted code. If this is a new workaround, I would rather like to
>>>>>>>> put it
>>>>>>>> in a separate patch for bisecting (can offer to do that myself then).
>>>>>>>> What are the symptoms? I am testing all these patches with OHW.
>>>>>>> Old code does (error checking removed):
>>>>>>>>> -            bios_size = get_image_size(filename);
>>>>>>>>> -                bios_addr = (uint32_t)(-bios_size);
>>>>>>>>> -                bios_size = load_image_targphys(filename, bios_addr,
>>>>>>> Ie, bios_addr = -512KB (size of OHW blob) = 0xfff80000
>>>>>>> and firmware is loaded in the range 0xfff80000-0xffffffff
>>>>>>> OHW expects reset instruction pointer to be 0xfffffffc (not valid for
>>>>>>> 604, but that's not the point now), which contains a valid instruction.
>>>>>>> Note that range 0xfff00000-0xfff7ffff is empty.
>>>>>>> 
>>>>>>> Datasheet for raven says that firmware is at 0xfff00000, so I changed
>>>>>>> code to:
>>>>>>> +#define BIOS_SIZE (1024 * 1024)
>>>>>>> +                  bios_addr = (uint32_t)(-BIOS_SIZE);
>>>>>>> +                  bios_size = load_image_targphys(filename, bios_addr,
>>>>>>> +                                                  bios_size);
>>>>>>> Ie, bios_addr = -1MB = 0xfff00000
>>>>>>> and firmware is loaded in the range 0xfff00000-0xfff7ffff.
>>>>>>> This doesn't work due to reset instruction pointer which now is
>>>>>>> pointing to empty memory, and symptoms are an empty screen on OHW.
>>>>>>> 
>>>>>>> So, I'm adding this hack for OHW, to mirror the 0xfff00000-0xfff7ffff
>>>>>>> range to 0xfff80000-0xffffffff.
>>>>>>> 
>>>>>>> So, this patch is a small functional change, as it adds a copy of the
>>>>>>> firmware in a new range 0xfff00000-0xfff7ffff, but I think we can
>>>>>>> live with it.
>>>>>>> 
>>>>>>> We'll be able to remove it once we switch to another firmware which
>>>>>>> uses the right reset instruction pointer or whose size is 1MB.
>>>>>> Couldn't we just make the ROM fill the upper part of the 1MB region
>>>>>> when we see it's smaller than 1MB? So that we pad at the bottom, not
>>>>>> the top?
>>>>>> 
>>>>>> bios_size = get_image_size(filename);
>>>>>> if (bios_size < 0) {
>>>>>>   // error handling
>>>>>> }
>>>>>> assert(bios_size <= (1*MB));
>>>>>> bios_addr = (uint32_t)(-bios_size);
>>>>>> 
>>>>> I don't think that's a good idea, because the PReP cpus (601/604) have a
>>>>> reset vector at 0xfff00100. So you have to put some firmware at this
>>>>> address, even if firmware is smaller than 1MB.
>>>>> 
>>>>> OHW is the problem here, because it is less than 1MB and expects a reset
>>>>> vector at 0xfffffffc. That's why I want to put the hack outside raven
>>>>> chipset, in prep machine code.
>>>> Let me clarify then that it was me who disabled some checks that used to
>>>> assure that the loaded binary is in fact 1MB:
>>>> http://git.qemu.org/?p=qemu.git;a=commit;h=74145374bfc0b7b02415184606236f0390479deb
>>>> So the issue is actually that the OHW binary is really messed up.
>>>> And me, Hervé and Mark have been working on getting OpenBIOS working for
>>>> PReP in its place.
>>>> So I'm currently considering the following options:
>>>> 1)
>>>> Revert OHW alias and size/position change
>>>> Strip ELF loading and elf-machine
>>>> Add back Raven ELF support separately
>>>> 2)
>>>> Apply my prep.c ELF support patch first
>>>> Apply this patch as pure loading-logic movement
>>>> 3)
>>>> Leave broken OHW loading in prep.c
>>>> Only implement 1MB / ELF loading support in Raven
>>>> 4)
>>>> Accept a 1MB OHW image and drop support for 512KB OHW
>> 
>> I like this option the best.
> 
> Alex, are you volunteering to build one? You wanted to look into that
> with me since a looong time ago... :)

You got mail kupo :).


Alex