On 10/18/2016 01:56 PM, Simon Glass wrote:
Hi Stephen,
On 18 October 2016 at 13:10, Stephen Warren swarren@wwwdotorg.org wrote:
On 10/18/2016 01:03 PM, Simon Glass wrote:
Hi Stephen,
On 18 October 2016 at 12:58, Stephen Warren swarren@wwwdotorg.org wrote:
On 10/18/2016 10:23 AM, Simon Glass wrote:
Hi Stephen,
On 17 October 2016 at 15:35, Stephen Warren swarren@wwwdotorg.org wrote:
From: Stephen Warren swarren@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 swarren@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 uclass?
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.
If there is only ever one implementation, why do you need weak functions?
As I explicitly stated above, each SoC can have a different implementation, yet only a single implementation is ever needed for a particular U-Boot build.
Just call them directly.
The code is doing that, both before and after my patch.
I think in fact you mean that there can be no implementation (but perhaps an empty one), or one implementation. You are effectively using multiple weak functions to provide default code. I think it would be better if this were explicit.
I still think that the cache functions could do with a rethink.
In my opinion, this patch doesn't change the code structure at all. There is already an interface between the core (L1/L2) cache management code and the SoC-specific cache management code. That interface already uses a weak function to provide the default no-op implementation. This patch doesn't change any of that. All this patch does is fix that existing interface to cover all 3 combinations of dcache_flush, dcache_invalidate, and icache_invalidate, rather than just one of those combinations. It's more of a bug-fix than anything else.
If you want to rework this interface sometime, be my guest. However, I don't think it's fair to require that someone who simply wants to fix the existing code (in a way that is orthogonal to your desired interface refactoring) do that refactoring first, rather than doing it yourself.