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SubjectRe: drivers/clocksource/timer-pistachio.c:74:22: warning: variable 'overflow' set but not used
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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/?id=a47d7ef4550d08fb428ea4c3f1a9c71674212208
>> 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@intel.com>
>>
>> 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'

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




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