On 10/18/2016 01:03 PM, Simon Glass wrote:
Hi Stephen,

On 18 October 2016 at 12:58, Stephen Warren <swar...@wwwdotorg.org> wrote:
On 10/18/2016 10:23 AM, Simon Glass wrote:

Hi Stephen,

On 17 October 2016 at 15:35, Stephen Warren <swar...@wwwdotorg.org> wrote:

From: Stephen Warren <swar...@nvidia.com>

SoC-specific logic may be required for all forms of cache-wide
operations; invalidate and flush of both dcache and icache (note that
only 3 of the 4 possible combinations make sense, since the icache never
contains dirty lines). This patch adds an optional hook for all
implemented cache-wide operations, and renames the one existing hook to
better represent exactly which operation it is implementing. A dummy
no-op implementation of each hook is provided. These dummy
implementations are moved into C code, since there's no need to
implement them in assembly.

Signed-off-by: Stephen Warren <swar...@nvidia.com>
 arch/arm/cpu/armv8/cache.S                   |  6 ------
 arch/arm/cpu/armv8/cache_v8.c                | 23
 arch/arm/cpu/armv8/fsl-layerscape/lowlevel.S |  4 ++--
 arch/arm/include/asm/system.h                |  5 ++++-
 arch/arm/mach-tegra/tegra186/cache.c         |  2 +-
 5 files changed, 27 insertions(+), 13 deletions(-)

I think we should have a proper interface for this stuff rather than
weak functions. Maybe we need a linker-list approach, or a cache

What's improper about this interface? Presumably we could argue that no
function in the entire of U-Boot be called by symbol name, which doesn't
seem useful.

I'm not sure exactly what you envisage by a linker-list approach. Can you
provide some background? I understand how the linker can construct list of
objects/implementations/..., but that doesn't seem useful here since there's
a known-ahead-of-time single implementation of these functions in a single
build of U-Boot.

Your own commit messages says that this is SoC-specific. I'm
suggesting that we define an interface (which I think you have already
done with your header file additions), and allow SoCs to implement it
via a linker list.

IMO the cache code in U-Boot is starting to get a bit creaky.

A cache uclass seems like /massive/ overkill, especially since I'd expect
these very low-level functions to be required well before any higher level
code like DM/classes/... to be available.

DM is available very early. But it's not clear from your patch when
this code is actually called.

I believe that weak functions are a perfectly acceptable approach here.

Yes, the implementation of these functions is SoC-specific. The Makefiles will pull in the appropriate implementation for that SoC whenever U-Boot is built, just like every other board- or SoC-specific function in the entire of U-Boot.

There's no need for linker lists since there is only ever one implementation.
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