[arm-platforms:timers/tval-ectomy 2/17] drivers/clocksource/arm_arch_timer.c:156:3: warning: variable 'val' is used uninitialized whenever switch default is taken

kernel test robot
2021-10-09T21:15:10Z

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tree: https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git timers/tval-ectomy
head: c815d60a6292c90ea228c635b4150f022322908b
commit: 9c6e4aa680ebd5ad816fc8f97858ec6057362c9e [2/17] clocksource/arm_arch_timer: Drop CNT*_TVAL read accessors
config: arm64-randconfig-r026-20211010 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 30caca39f401ae17927439c0a0bd6d1b1916dd6a)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install arm64 cross compiling tool for clang build
# apt-get install binutils-aarch64-linux-gnu
# https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?id=9c6e4aa680ebd5ad816fc8f97858ec6057362c9e
git remote add arm-platforms https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git
git fetch --no-tags arm-platforms timers/tval-ectomy
git checkout 9c6e4aa680ebd5ad816fc8f97858ec6057362c9e
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=arm64

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> drivers/clocksource/arm_arch_timer.c:156:3: warning: variable 'val' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
default:
^~~~~~~
drivers/clocksource/arm_arch_timer.c:163:9: note: uninitialized use occurs here
return val;
^~~
drivers/clocksource/arm_arch_timer.c:147:3: warning: variable 'val' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
default:
^~~~~~~
drivers/clocksource/arm_arch_timer.c:163:9: note: uninitialized use occurs here
return val;
^~~
drivers/clocksource/arm_arch_timer.c:139:9: note: initialize the variable 'val' to silence this warning
u32 val;
^
= 0
2 warnings generated.

vim +/val +156 drivers/clocksource/arm_arch_timer.c

f4e00a1a55c7f9 Marc Zyngier 2017-01-20 134
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 135 static __always_inline
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 136 u32 arch_timer_reg_read(int access, enum arch_timer_reg reg,
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 137 struct clock_event_device *clk)
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 138 {
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 139 u32 val;
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 140
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 141 if (access == ARCH_TIMER_MEM_PHYS_ACCESS) {
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 142 struct arch_timer *timer = to_arch_timer(clk);
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 143 switch (reg) {
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 144 case ARCH_TIMER_REG_CTRL:
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 145 val = readl_relaxed(timer->base + CNTP_CTL);
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 146 break;
0bc2c9327c236c Marc Zyngier 2021-09-20 147 default:
0bc2c9327c236c Marc Zyngier 2021-09-20 148 BUILD_BUG();
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 149 }
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 150 } else if (access == ARCH_TIMER_MEM_VIRT_ACCESS) {
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 151 struct arch_timer *timer = to_arch_timer(clk);
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 152 switch (reg) {
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 153 case ARCH_TIMER_REG_CTRL:
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 154 val = readl_relaxed(timer->base + CNTV_CTL);
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 155 break;
0bc2c9327c236c Marc Zyngier 2021-09-20 @156 default:
0bc2c9327c236c Marc Zyngier 2021-09-20 157 BUILD_BUG();
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 158 }
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 159 } else {
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 160 val = arch_timer_reg_read_cp15(access, reg);
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 161 }
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 162
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 163 return val;
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 164 }
f4e00a1a55c7f9 Marc Zyngier 2017-01-20 165

:::::: The code at line 156 was first introduced by commit
:::::: 0bc2c9327c236c28cdb2784d11ca349ef3b1ca0a clocksource/arm_arch_timer: Add build-time guards for unhandled register accesses

:::::: TO: Marc Zyngier <maz@kernel.org>
:::::: CC: Marc Zyngier <maz@kernel.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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