[U-Boot] [RFC] New init sequence processing without init_sequence array

[Graeme Russ]

Hi Mike

On Tue, Aug 23, 2011 at 11:00 AM, Mike Frysinger <vapier at gentoo.org> wrote:
> On Monday, August 22, 2011 16:10:23 Wolfgang Denk wrote:
>> 3. Hardware initialization in inherently very much hardware depen-
>>    dent ;-)  We have some boards where PCI must be initialized early
>>    because it is needed to access some other peripherals like memory.
>>    And we have other boards where PCI can only be initialized late
>>    because it depends on a lot of other functions that must be working
>>    first.
>>
>>    I explained this a number of times before: the current code was
>>    designed to allow even for completely board specific init
>>    sequences, by simply adding #define for the list of init functions
>>    to the board config file - see for example here:
>>
>>    http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/33951/focus=36436
>>
>>    http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/72131/focus=72136
>>
>>    If you look at the current code - heavily larded with #ifdefs of
>>    all shapes and colors - I cannot see any good way to transform this
>>    into an initcall (and thus sequence number based) implementation.
>>    Do you have any specific ideas how to address this?
>
> if the funcs get merged by the linker script, the board still has full control
> over the init order by writing their own linker script

Hmm, I hadn't thought of that as a solution. It would work, but i think it
is very fragile. The way I have done the INIT_FUNC macro, each function
gets assigned to an (otherwise unused) variable which is given it's own
section in the link with each section being named with a .<step number>
at the end. Now doing SORT_BY_NAME makes sure all the sections are in the
right order and that all sections (and therefore variables, and therefore
init functions) are included.

To re-order the function in the linker script would mean individually
specifying each and every section in the boards linker script. If another
function get added at the arch level, there is a great chance that this new
linker section would not get included in any board specific linker script

Regards,

Graeme