[U-Boot] [PATCH v2 1/3] Revert "arm: Replace v7_maint_dcache_all(ARMV7_DCACHE_CLEAN_INVAL_ALL) with asm code"

[Tom Rini]

On Fri, Jul 22, 2016 at 10:40:11AM -0400, Sandy Patterson wrote:

> Commit c09d29057a and df120142f36 break kernel loading on rock2 board.
> 
> console output:
> Starting kernel ...
> 
> ### ERROR ### Please RESET the board ###
> 
> This reverts commit c09d29057ab0b04db0857d319c6bff74de31b9c3.
> 
> Conflicts:
> 	arch/arm/cpu/armv7/cache_v7.c
> 	arch/arm/cpu/armv7/cache_v7_asm.S
> 
> Signed-off-by: Sandy Patterson <apatterson at sightlogix.com>

So, we cannot do this.  The problem is two-fold.  First, newer GCCs will
cause failure to boot with the way the code was, which is how we found
this problem.  The second is that after some offline conversations with
ARM Ltd people (and some other smart folks too, these operations cannot
safely be done in C, there's just no way.  So we borrowed what the
kernel does.  You need to figure out what behavior the (old?) kernel is
relying on and either emulate that with a flag (like sunxi does, or at
least did, at one point for some other issues of correct behavior vs
existing kernels) or just not support those older kernels.

-- 
Tom
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