From: Wolfgang Wegner <wolfgang@leila.ping.de>
Date: Thu, 21 Jan 2010 18:37:35 +0100
Subject: [U-Boot] [MCF5445x] board-specific SDRAM setup in assembler - how
	to do it correctly?
Message-ID: <20100121173735.GI23389@leila.ping.de>
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To: u-boot@lists.denx.de

Hi list,

I am trying to cleanly integrate a new coldfire MCF5445x-based board
into U-Boot. The problem I have is:
- the board is booted from serial flash, meaning that SDRAM setup has
  to be done in assembler from a small pre-loader
- the existing code for this already has some #ifdefs for handling
  different evaluation boards
- I would like to be able to switch between 2 or 3 board assembly
  options requiring different memory setup, possibly by reading
  GPIOs used as strap pins.

The existing code is in cpu/mcf5445x/start.S. My idea would be to
make the actual SDRAM init (ll. 190-284) conditional:
#if defined(BOARD_ASM_SDRAM_INIT)
BOARD_ASM_SDRAM_INIT
#else
[ll.190-284]
#endif

BOARD_SDRAM_INIT could be #defined in our board configuration header.

Like this the global code would not be cluttered with #ifdefs, but
some parts of course would be duplicated.
I see no straight-forward way to set the part and board specific
register values in a generic manner if the actual values shall also
be depending on board-specific GPIO pins.

Is there any objection against such an implementation, or any other
example how this could be done in a better way?

Regards,
Wolfgang