[PATCH 1/3] cmd: avoid duplicate weak flush_dcache_all()

[Ilias Apalodimas]

On Wed, 19 Jun 2024 at 15:36, Heinrich Schuchardt
<heinrich.schuchardt at canonical.com> wrote:
>
> On 19.06.24 14:23, Ilias Apalodimas wrote:
> > On Sun, 16 Jun 2024 at 20:31, Heinrich Schuchardt
> > <heinrich.schuchardt at canonical.com> wrote:
> >>
> >> If we have multiple weak implementations of functions, the linker might
> >> choose any of these. ARM and RISC-V already provide a weak implementation
> >> of flush_dcache_all().
> >>
> >> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> >> ---
> >>   cmd/cache.c | 3 +++
> >>   1 file changed, 3 insertions(+)
> >>
> >> diff --git a/cmd/cache.c b/cmd/cache.c
> >> index 0254ff17f9b..16fa0f7c652 100644
> >> --- a/cmd/cache.c
> >> +++ b/cmd/cache.c
> >> @@ -52,11 +52,14 @@ static int do_icache(struct cmd_tbl *cmdtp, int flag, int argc,
> >>          return 0;
> >>   }
> >>
> >> +/* ARM and RISC-V define a weak flush_dcache_all() themselves. */
> >> +#if !defined(CONFIG_ARM) && !defined(CONFIG_RISCV)
> >>   void __weak flush_dcache_all(void)
> >>   {
> >>          puts("No arch specific flush_dcache_all available!\n");
> >>          /* please define arch specific flush_dcache_all */
> >>   }
> >
> > Aren't we supposed to add a single __weak function so the linker can
> > replace it? IOW why is the declaration for Arm/riscv a weak one?
>
> Some sub-architectures override the architecture specific weak
> implementation, e.g.
>
> arch/riscv/cpu/andes/cache.c:44:
> void flush_dcache_all(void)
>
> arch/arm/cpu/arm926ejs/cache.c:17:
> void flush_dcache_all(void)

Ok, this does fix a problem, but afaict this is a band-aid and the
cache management is a mess overall -- e.g invalidate_icache_all() will
suffer from the same issue if a sub-architecture decides to define its
own in the future.

Would it be less bad to define
static inline __weak flush_dcache_all(void)
{
}
static inline __weak flush_icache_all(void)
{
}
in include/cpu_func.h instead of a random cmd file?
We can only define those if !CONFIG_ARM && !!CONFIG_RISCV and add a
comment on why.
It's kind of putting lipstick on a pig, but at least we'll have them
gathered in a single header file and know what we have to fix.

Cheers
/Ilias
>
> Best regards
>
> Heinrich
>
> >
> > Thanks
> > /Ilias
> >> +#endif
> >>
> >>   static int do_dcache(struct cmd_tbl *cmdtp, int flag, int argc,
> >>                       char *const argv[])
> >> --
> >> 2.43.0
> >>
>