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

Hello Arnd,

On Fri, Mar 21, 2014 at 04:10:37PM +0100, Arnd Bergmann wrote:

On Friday 21 March 2014 15:32:24 Uwe Kleine-K?nig wrote:

quoted

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

quoted

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

I don't see a reason to change the existing logic, it works for
both MMU and NOMMU kernels, and you are talking about *three* instructions
here.

it doesn't matter how many instructions are involved. The relevant
difference is that with my approach you fix the problem for all no-MMU
platforms, with yours you only fix efm32. (OK, I think there are not too
many no-MMU platforms, but still.) An even easier implementation would
be to add something like:

	ifeq($(zreladdr-y)$(CONFIG_MMU),)
	zreladdr-y := CONFIG_PAGE_OFFSET + CONFIG_TEXT_OFFSET
	endif

to arch/arm/boot/Makefile.

But I don't care much, if you still want to make EFM32 select
AUTO_ZRELADDR go ahead.

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-K?nig            |
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