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

From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH v3 03/10] raven: move BIOS loading from board code to PCI host
Date: Mon, 23 Dec 2013 11:24:33 +0100

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);


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