linux/dim: Do nothing if no time delta between samples

Add return value for dim_calc_stats. This is an indication for the
caller if curr_stats was assigned by the function. Avoid using
curr_stats uninitialized over {rdma/net}_dim, when no time delta between
samples. Coverity reported this potential use of an uninitialized
variable.

Fixes: 4c4dbb4a7363 ("net/mlx5e: Move dynamic interrupt coalescing code to include/linux")
Fixes: cb3c7fd4f839 ("net/mlx5e: Support adaptive RX coalescing")
Signed-off-by: Roy Novich <royno@nvidia.com>
Reviewed-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Link: https://lore.kernel.org/r/20230507135743.138993-1-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

dim: initialize all struct fields

The W=2 build pointed out that the code wasn't initializing all the
variables in the dim_cq_moder declarations with the struct initializers.
The net change here is zero since these structs were already static
const globals and were initialized with zeros by the compiler, but
removing compiler warnings has value in and of itself.

lib/dim/net_dim.c: At top level:
lib/dim/net_dim.c:54:9: warning: missing initializer for field ‘comps’ of ‘const struct dim_cq_moder’ [-Wmissing-field-initializers]
54 | NET_DIM_RX_EQE_PROFILES,
| ^~~~~~~~~~~~~~~~~~~~~~~
In file included from lib/dim/net_dim.c:6:
./include/linux/dim.h:45:13: note: ‘comps’ declared here
45 | u16 comps;
| ^~~~~

and repeats for the tx struct, and once you fix the comps entry then
the cq_period_mode field needs the same treatment.

Use the commonly accepted style to indicate to the compiler that we
know what we're doing, and add a comma at the end of each struct
initializer to clean up the issue, and use explicit initializers
for the fields we are initializing which makes the compiler happy.

While here and fixing these lines, clean up the code slightly with
a fix for the super long lines by removing the word "_MODERATION" from a
couple defines only used in this file.

Fixes: f8be17b81d44 ("lib/dim: Fix -Wunused-const-variable warnings")
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Link: https://lore.kernel.org/r/20220507011038.14568-1-jesse.brandeburg@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Revert "lib: Revert use of fallthrough pseudo-keyword in lib/"

This reverts commit 6a9dc5fd6170 ("lib: Revert use of fallthrough
pseudo-keyword in lib/")

Now that we can build arch/powerpc/boot/ free of -Wimplicit-fallthrough,
re-enable these fixes for lib/.

Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/236
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

lib: Revert use of fallthrough pseudo-keyword in lib/

The following build error for powerpc64 was reported by Nathan Chancellor:

"$ scripts/config --file arch/powerpc/configs/powernv_defconfig -e KERNEL_XZ

$ make -skj"$(nproc)" ARCH=powerpc CROSS_COMPILE=powerpc64le-linux- distclean powernv_defconfig zImage
...
In file included from arch/powerpc/boot/../../../lib/decompress_unxz.c:234,
from arch/powerpc/boot/decompress.c:38:
arch/powerpc/boot/../../../lib/xz/xz_dec_stream.c: In function 'dec_main':
arch/powerpc/boot/../../../lib/xz/xz_dec_stream.c:586:4: error: 'fallthrough' undeclared (first use in this function)
586 | fallthrough;
| ^~~~~~~~~~~

This will end up affecting distribution configurations such as Debian
and OpenSUSE according to my testing. I am not sure what the solution
is, the PowerPC wrapper does not set -D__KERNEL__ so I am not sure
that compiler_attributes.h can be safely included."

In order to avoid these sort of problems, it seems that the best
solution is to use /* fall through */ comments instead of the
fallthrough pseudo-keyword macro in lib/, for now.

Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Fixes: df561f6688fe ("treewide: Use fallthrough pseudo-keyword")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-and-tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

treewide: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

lib/dim: Fix -Wunused-const-variable warnings

DIM causes to the following warnings during kernel compilation
which indicates that tx_profile and rx_profile are supposed to
be declared in *.c and not in *.h files.

In file included from ./include/rdma/ib_verbs.h:64,
from ./include/linux/mlx5/device.h:37,
from ./include/linux/mlx5/driver.h:51,
from ./include/linux/mlx5/vport.h:36,
from drivers/infiniband/hw/mlx5/ib_virt.c:34:
./include/linux/dim.h:326:1: warning: _tx_profile_ defined but not used [-Wunused-const-variable=]
326 | tx_profile[DIM_CQ_PERIOD_NUM_MODES][NET_DIM_PARAMS_NUM_PROFILES] = {
| ^~~~~~~~~~
./include/linux/dim.h:320:1: warning: _rx_profile_ defined but not used [-Wunused-const-variable=]
320 | rx_profile[DIM_CQ_PERIOD_NUM_MODES][NET_DIM_PARAMS_NUM_PROFILES] = {
| ^~~~~~~~~~

Fixes: 4f75da3666c0 ("linux/dim: Move implementation to .c files")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

linux/dim: Move implementation to .c files

Moved all logic from dim.h and net_dim.h to dim.c and net_dim.c.
This is both more structurally appealing and would allow to only
expose externally used functions.

Signed-off-by: Tal Gilboa <talgi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>