[U-Boot] [PATCH v2 5/5] x86: Remove unused real mode code

[Graeme Russ]

Hi Simon,

On Fri, Feb 15, 2013 at 2:35 PM, Simon Glass <sjg at chromium.org> wrote:
> Hi Graeme,
>
> On Thu, Feb 14, 2013 at 2:36 PM, Graeme Russ <graeme.russ at gmail.com> wrote:
>> Hi Simon,
>>
>> On Fri, Feb 15, 2013 at 1:18 AM, Simon Glass <sjg at chromium.org> wrote:
>>> This code is pretty old and we want to support only 32-bit systems now.
>>> Keep the real mode-to-protected code in case we want to boot an x86 from
>>> power-up, but invert the polarity of the option.
>>>
>>> Signed-off-by: Simon Glass <sjg at chromium.org>

[snip]

>>> diff --git a/README b/README
>>> index 6106e0d..7b50720 100644
>>> --- a/README
>>> +++ b/README
>>> @@ -3820,10 +3820,9 @@ Low Level (hardware related) configuration options:
>>>                 If defined, the x86 reset vector code is included. This is not
>>>                 needed when U-Boot is running from Coreboot.
>>>
>>> -- CONFIG_X86_NO_REAL_MODE
>>> -               If defined, x86 real mode code is omitted. This assumes a
>>> -               32-bit environment where such code is not needed. You will
>>> -               need to do this when U-Boot is running from Coreboot.
>>> +- CONFIG_X86_REAL_MODE
>>> +               If defined, some 86 real mode code is included. This is not
>>> +               needed when U-Boot is running from Coreboot.
>>
>> I think this config option can be punted completely. This define is
>> only used to pull in the real-mode trampoline code which switches from
>> protected-mode to real-mode before jumping into the Linux kernel's
>> real-mode stub. The code for the initial real-mode to protected-mode
>> switch will be pulled in by CONFIG_X86_RESET_VECTOR
>
> I suppose I am confused about what is needed here. I will drop the
> flag, and arch/x86/lib/realmode_switch.S. Is that right?

Correct. All you need to keep is:

arch/x86/cpu/resetvec.S
arch/x86/cpu/start16

And these are conditional on CONFIG_X86_RESET_VECTOR

Looking at the most recent patch, I think you have it nailed now

Regards,

Graeme