From:   Nathan Chancellor <nathan@kernel.org>
To:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev, Nathan Chancellor <nathan@kernel.org>,
        =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= <mirq-linux@rere.qmqm.pl>
Subject: [PATCH v2] soc/tegra: fuse: Fix bitwise vs. logical OR warning
Date:   Fri, 10 Dec 2021 09:55:29 -0700
Message-Id: <20211210165528.3232292-1-nathan@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

A new warning in clang points out two instances where boolean
expressions are being used with a bitwise OR instead of logical OR:

drivers/soc/tegra/fuse/speedo-tegra20.c:72:9: warning: use of bitwise '|' with boolean operands [-Wbitwise-instead-of-logical]
                reg = tegra_fuse_read_spare(i) |
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~
                                               ||
drivers/soc/tegra/fuse/speedo-tegra20.c:72:9: note: cast one or both operands to int to silence this warning
drivers/soc/tegra/fuse/speedo-tegra20.c:87:9: warning: use of bitwise '|' with boolean operands [-Wbitwise-instead-of-logical]
                reg = tegra_fuse_read_spare(i) |
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~
                                               ||
drivers/soc/tegra/fuse/speedo-tegra20.c:87:9: note: cast one or both operands to int to silence this warning
2 warnings generated.

The motivation for the warning is that logical operations short circuit
while bitwise operations do not.

In this instance, tegra_fuse_read_spare() is not semantically returning
a boolean, it is returning a bit value. Use u32 for its return type so
that it can be used with either bitwise or boolean operators without any
warnings.

Fixes: 25cd5a391478 ("ARM: tegra: Add speedo-based process identification")
Link: https://github.com/ClangBuiltLinux/linux/issues/1488
Suggested-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---

v1 -> v2: https://lore.kernel.org/r/20211021214500.2388146-1-nathan@kernel.org/

* Change return type of tegra_fuse_read_spare(), instead of changing
  bitwise OR to logical OR in tegra20_init_speedo_data() (Michał).

It would be nice to get this fixed sooner rather than later, as ARCH=arm
allmodconfig is broken due to -Werror.

 drivers/soc/tegra/fuse/fuse-tegra.c | 2 +-
 drivers/soc/tegra/fuse/fuse.h       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/tegra/fuse/fuse-tegra.c b/drivers/soc/tegra/fuse/fuse-tegra.c
index f2151815db58..e714ed3b61bc 100644
--- a/drivers/soc/tegra/fuse/fuse-tegra.c
+++ b/drivers/soc/tegra/fuse/fuse-tegra.c
@@ -320,7 +320,7 @@ static struct platform_driver tegra_fuse_driver = {
 };
 builtin_platform_driver(tegra_fuse_driver);
 
-bool __init tegra_fuse_read_spare(unsigned int spare)
+u32 __init tegra_fuse_read_spare(unsigned int spare)
 {
 	unsigned int offset = fuse->soc->info->spare + spare * 4;
 
diff --git a/drivers/soc/tegra/fuse/fuse.h b/drivers/soc/tegra/fuse/fuse.h
index de58feba0435..ecff0c08e959 100644
--- a/drivers/soc/tegra/fuse/fuse.h
+++ b/drivers/soc/tegra/fuse/fuse.h
@@ -65,7 +65,7 @@ struct tegra_fuse {
 void tegra_init_revision(void);
 void tegra_init_apbmisc(void);
 
-bool __init tegra_fuse_read_spare(unsigned int spare);
+u32 __init tegra_fuse_read_spare(unsigned int spare);
 u32 __init tegra_fuse_read_early(unsigned int offset);
 
 u8 tegra_get_major_rev(void);

base-commit: 0fcfb00b28c0b7884635dacf38e46d60bf3d4eb1
-- 
2.34.1