[PATCH 10/62] ARM: efm32: select AUTO_ZRELADDR

Hello Arnd,

On Thu, Mar 20, 2014 at 11:16:20PM +0100, Arnd Bergmann wrote:

On Thursday 20 March 2014 21:48:47 Uwe Kleine-K?nig wrote:

quoted

On Wed, Mar 19, 2014 at 08:29:07PM +0100, Arnd Bergmann wrote:

quoted

The efm32 platform does not provide a zreladdr-y line its Makefile.boot,
so we always have to use CONFIG_AUTO_ZRELADDR in order to successfully
build and link a zImage.

I wonder why you need to AUTO_ZRELADDR (which is there to guess
zreladdr) while efm32 doesn't have an MMU and so there is nothing to
guess. So I think this patch fixes a build problem, but it's not a good
change.

It is required in order to build a compressed zImage file. You mentioned
before that your system does not have enough RAM to support this, but
the compile-time option exists, and there is no dependency on MMU support
for it, nor should there be.

My objection isn't about having only little RAM. AUTO_ZRELADDR is about
guessing the physical address corresponding to PAGE_OFFSET. But without
an MMU there is nothing to guess. So I wonder if the better change would
be to do:

	#ifdef CONFIG_MMU
	#ifdef CONFIG_AUTO_ZRELADDR
		... guess zreladdress based on instruction pointer
	#else
		... use zreladdr from Makefile.boot
	#endif
	#else
		... use zreladdr = PAGE_OFFSET
	#endif

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |