Messages in this thread | | | From | Barry Song <> | Date | Wed, 20 Mar 2024 12:22:56 +1300 | Subject | Re: [PATCH v2] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros |
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On Wed, Mar 20, 2024 at 3:18 AM Guenter Roeck <linux@roeck-us.net> wrote: > > On 3/18/24 18:27, Barry Song wrote: > > On Tue, Mar 19, 2024 at 2:09 PM Barry Song <21cnbao@gmail.com> wrote: > >> > >> From: Barry Song <v-songbaohua@oppo.com> > >> > >> xtensa's flush_dcache_page() can be a no-op sometimes. There is a > >> generic implementation for this case in include/asm-generic/ > >> cacheflush.h. > >> #ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE > >> static inline void flush_dcache_page(struct page *page) > >> { > >> } > >> > >> #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0 > >> #endif > >> > >> So remove the superfluous flush_dcache_page() definition, which also > >> helps silence potential build warnings complaining the page variable > >> passed to flush_dcache_page() is not used. > >> > >> In file included from crypto/scompress.c:12: > >> include/crypto/scatterwalk.h: In function 'scatterwalk_pagedone': > >> include/crypto/scatterwalk.h:76:30: warning: variable 'page' set but not used [-Wunused-but-set-variable] > >> 76 | struct page *page; > >> | ^~~~ > >> crypto/scompress.c: In function 'scomp_acomp_comp_decomp': > >>>> crypto/scompress.c:174:38: warning: unused variable 'dst_page' [-Wunused-variable] > >> 174 | struct page *dst_page = sg_page(req->dst); > >> | > >> > >> The issue was originally reported on LoongArch by kernel test > >> robot (Huacai fixed it on LoongArch), then reported by Guenter > >> and me on xtensa. > >> > >> This patch also removes lots of redundant macros which have > >> been defined by asm-generic/cacheflush.h. > >> > >> Cc: Huacai Chen <chenhuacai@loongson.cn> > >> Cc: Herbert Xu <herbert@gondor.apana.org.au> > >> Reported-by: kernel test robot <lkp@intel.com> > >> Closes: https://lore.kernel.org/oe-kbuild-all/202403091614.NeUw5zcv-lkp@intel.com/ > >> Reported-by: Barry Song <v-songbaohua@oppo.com> > >> Closes: https://lore.kernel.org/all/CAGsJ_4yDk1+axbte7FKQEwD7X2oxUCFrEc9M5YOS1BobfDFXPA@mail.gmail.com/ > >> Reported-by: Guenter Roeck <linux@roeck-us.net> > > > > Hi Guenter, > > I am not a xtensa guy, so I will need your help for a full test. if > > turns out it is a too big(ambitious) > > I sent a Tested-by: tag to your patch. As far as my testing goes, it works fine, > and I added your patch to my "testing" branch (which tries to be buildable > and testable for all architectures).
Thank you very much, Guenter. It would be nice if xtensa can leverage the common cacheflush.h just like other architectures.
> > > fix, a minimal fix might be: > > > > FWIW, I think a minimal fix would have been to mark the variable as __maybe_unused,
I am not quite sure we want this as the point is that drivers should be independent of architectural differences.
The driver code, for itself, seems quite innocent,
struct page *dst_page = sg_page(req->dst);
for (i = 0; i < nr_pages; i++) flush_dcache_page(dst_page + i);
The only problem is that xtensa's flush_dcache_page is a macro and doesn't use the "page" parameter. if we re-use the inline function in common cacheflush.h, it won't be a problem.
> but as others have pointed out it would be nice if there would be a guidance > about optional API functions like this one that specifies if it may be > implemented as macro and, if so, how it has to handle unused variables.
I agree. personally I like this and will have a go in Documentation/process/coding-style.rst and see others' opinions.
> > Thanks, > Guenter
Thanks Barry
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