On Fri, Nov 12, 2021 at 07:05:48AM +0800, kernel test robot wrote: > Hi Drew, > > FYI, the error/warning still remains. > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > head: debe436e77c72fcee804fb867f275e6d31aa999c > commit: a47d7ef4550d08fb428ea4c3f1a9c71674212208 clocksource/drivers/pistachio: Fix trivial typo > date: 7 months ago > config: mips-randconfig-r012-20210927 (attached as .config) > compiler: mips-linux-gcc (GCC) 11.2.0 > 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 > # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... > git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > git fetch --no-tags linus master > git checkout a47d7ef4550d08fb428ea4c3f1a9c71674212208 > # save the attached .config to linux build tree > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=mips > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot <lkp(a)intel.com&gt; > > All warnings (new ones prefixed by >>): > > drivers/clocksource/timer-pistachio.c: In function 'pistachio_clocksource_read_cycles': >>> drivers/clocksource/timer-pistachio.c:74:22: warning: variable 'overflow' set but not used [-Wunused-but-set-variable] > 74 | u32 counter, overflow; > | ^~~~~~~~ > > > vim +/overflow +74 drivers/clocksource/timer-pistachio.c > > 69 > 70 static u64 notrace > 71 pistachio_clocksource_read_cycles(struct clocksource *cs) > 72 { > 73 struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs); > > 74 u32 counter, overflow; > 75 unsigned long flags; > 76 > 77 /* > 78 * The counter value is only refreshed after the overflow value is read. > 79 * And they must be read in strict order, hence raw spin lock added. > 80 */ > 81 > 82 raw_spin_lock_irqsave(&pcs->lock, flags); > 83 overflow = gpt_readl(pcs->base, TIMER_CURRENT_OVERFLOW_VALUE, 0);

I fail to see how variable 'overflow' set but not used as the return value of gpt_readl() is unconditionally assigned to 'overflow'.

On Sun, Nov 14, 2021 at 11:17:38PM +0100, Daniel Lezcano wrote: > On 14/11/2021 22:29, Drew Fustini wrote: >> On Fri, Nov 12, 2021 at 07:05:48AM +0800, kernel test robot wrote: >>> Hi Drew, >>> >>> FYI, the error/warning still remains. >>> >>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master >>> head: debe436e77c72fcee804fb867f275e6d31aa999c >>> commit: a47d7ef4550d08fb428ea4c3f1a9c71674212208 clocksource/drivers/pistachio: Fix trivial typo >>> date: 7 months ago >>> config: mips-randconfig-r012-20210927 (attached as .config) >>> compiler: mips-linux-gcc (GCC) 11.2.0 >>> 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 >>> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... >>> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git >>> git fetch --no-tags linus master >>> git checkout a47d7ef4550d08fb428ea4c3f1a9c71674212208 >>> # save the attached .config to linux build tree >>> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=mips >>> >>> If you fix the issue, kindly add following tag as appropriate >>> Reported-by: kernel test robot <lkp(a)intel.com&gt; >>> >>> All warnings (new ones prefixed by >>): >>> >>> drivers/clocksource/timer-pistachio.c: In function 'pistachio_clocksource_read_cycles': >>>>> drivers/clocksource/timer-pistachio.c:74:22: warning: variable 'overflow' set but not used [-Wunused-but-set-variable] >>> 74 | u32 counter, overflow; >>> | ^~~~~~~~ >>> >>> >>> vim +/overflow +74 drivers/clocksource/timer-pistachio.c >>> >>> 69 >>> 70 static u64 notrace >>> 71 pistachio_clocksource_read_cycles(struct clocksource *cs) >>> 72 { >>> 73 struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs); >>> > 74 u32 counter, overflow; >>> 75 unsigned long flags; >>> 76 >>> 77 /* >>> 78 * The counter value is only refreshed after the overflow value is read. >>> 79 * And they must be read in strict order, hence raw spin lock added. >>> 80 */ >>> 81 >>> 82 raw_spin_lock_irqsave(&pcs->lock, flags); >>> 83 overflow = gpt_readl(pcs->base, TIMER_CURRENT_OVERFLOW_VALUE, 0); > > overflow is set here but then never reused in the function. So a call to > gpt_readl without getting the return value is fine. > > The warning is different from 'variable is unused' Thank you for pointing that out. I was reading it incorrectly. As for this function, it seems that warning is a false positive as the act of reading TIMER_CURRENT_OVERFLOW_VALUE causes the hardware to refresh TIMER_CURRENT_VALUE.