[U-Boot] [Patch v3 1/2] common/board_f: Preserve early global data

[Scott Wood]

On Thu, 2014-05-01 at 14:29 -0700, York Sun wrote:
> On 05/01/2014 02:21 PM, Scott Wood wrote:
> > On Thu, 2014-05-01 at 14:16 -0700, York Sun wrote:
> >> On 05/01/2014 08:54 AM, Simon Glass wrote:
> >>> Hi York,
> >>>
> >>> On 30 April 2014 18:01, York Sun <yorksun at freescale.com> wrote:
> >>>> Some platforms (including mpc85xx, mpc86xx) use global data before calling
> >>>> function baord_inti_f(). This data should not be cleared later. Any arch
> >>>> which needs to preserve global data should define CONFIG_SYS_EARLY_GD.
> >>>>
> >>>> Signed-off-by: York Sun <yorksun at freescale.com>
> >>>> CC: Scott Wood <scottwood at freescale.com>
> >>>> CC: Simon Glass <sjg at chromium.org>
> >>>> ---
> >>>> Change log
> >>>>
> >>>>  v3: Introduce CONFIG_SYS_EARLY_GD instead of using a list
> >>>>  v2: Instead of adding back gd init for all PPC, preserve gd for mpc85xx and mpc86xx.
> >>>>
> >>>>  README                            |    3 +++
> >>>>  arch/powerpc/include/asm/config.h |    2 ++
> >>>>  arch/x86/include/asm/config.h     |    1 +
> >>>>  common/board_f.c                  |   10 +++++-----
> >>>>  4 files changed, 11 insertions(+), 5 deletions(-)
> >>>>
> >>>> diff --git a/README b/README
> >>>> index 12758dc..1a51b11 100644
> >>>> --- a/README
> >>>> +++ b/README
> >>>> @@ -440,6 +440,9 @@ The following options need to be configured:
> >>>>                 supported, core will start to execute uboot when wakes up.
> >>>>
> >>>>  - Generic CPU options:
> >>>> +               CONFIG_SYS_EARLY_GD
> >>>> +               Defines global data is used before board_init_f().
> >>>> +
> >>>
> >>> This looks like a good solution, but I believe that 'early' is in fact
> >>> where we are headed. So perhaps you should create an inverted option
> >>> and define it for archs that don't support it?
> >>
> >> I don't disagree for the long term. But since we just start to convert to
> >> generic board, fewer archs need this than those don't. I suggest we try this and
> >> when most archs convert to generic board, we can invert it if needed.
> > 
> > Why wait to do it right?  Which arches actually don't need this, given
> > that Simon said he thinks ARM needs it as well?
> > 
> 
> Adding something I can't test?

By that rationale nobody could ever make changes that aren't localized
to a few boards.  That type of development produces the sort of mess
that the generic board is meant to remedy.

> Even Simon said he thinks ARM needs it, it is not what current code has. If I
> revert this logic,
> 
> #ifdef CONFIG_SYS_GLOBAL_DATA_STACK

This looks like a global stack of data, not global data on the stack.

How about CONFIG_SYS_GENERIC_GLOBAL_DATA?

>        gd_dt data;
> 
>        gd = &data;
>        zero_global_data();
> #endif
> 
> I need to add #define CONFIG_SYS_GLOBAL_DATA_STACK to the board/arch who needs
> it. I have no idea which needs in the 70+ boards with CONFIG_DISPLAY_BOARDINFO
> defined.

I see only 10 boards that currently use CONFIG_SYS_GENERIC_BOARD in
include/configs, plus sandbox and x86 which hide it in config.mk.  I
don't know what CONFIG_DISPLAY_BOARDINFO has to do with it.  To invert
the symbol, add the new symbol to all of the current users.  Removal
from ARM boards can come afterward if it's confirmed that it's the right
thing to do.

-Scott