Messages in this thread | | | Subject | Re: [PATCH] clocksource: kona: avoid bogus warning | From | Ray Jui <> | Date | Mon, 13 Jun 2016 15:34:38 -0700 |
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Hi Arnd,
On 6/13/2016 1:40 PM, Arnd Bergmann wrote: > I could not figure out why, but gcc cannot prove that the > kona_timer_init function always initializes its two outputs, > and we get a warning for the use of the 'lsw' variable later, > which is obviously correct. > > drivers/clocksource/bcm_kona_timer.c: In function 'kona_timer_init': > drivers/clocksource/bcm_kona_timer.c:119:13: error: 'lsw' may be used uninitialized in this function [-Werror=maybe-uninitialized] > > Slightly reordering the loop makes the warning disappear, after > it becomes more obvious to the compiler that the loop is > always entered on the first iteration. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > drivers/clocksource/bcm_kona_timer.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c > index 70d9c1e482dd..bbbfb03b46dd 100644 > --- a/drivers/clocksource/bcm_kona_timer.c > +++ b/drivers/clocksource/bcm_kona_timer.c > @@ -69,7 +69,7 @@ static void kona_timer_disable_and_clear(void __iomem *base) > static void > kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw) > { > - int loop_limit = 4; > + int loop_limit = 3; > > /* > * Read 64-bit free running counter > @@ -83,12 +83,12 @@ kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw) > * if new hi-word is equal to previously read hi-word then stop. > */ > > - while (--loop_limit) { > + do { > *msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET); > *lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET); > if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET)) > break; > - } > + } while (--loop_limit); > if (!loop_limit) { > pr_err("bcm_kona_timer: getting counter failed.\n"); > pr_err(" Timer will be impacted\n"); >
This fix of compiler warning looks fine to me.
Btw, this also exposes another issue in the code:
Does it make more sense to have "kona_timer_get_counter" return -ETIMEDOUT in the case when "loop_limit" reaches zero, and in "kona_timer_set_net_event", it should bail out immediately when error is returned from "kona_timer_get_counter":
ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw); if (ret) return ret;
Thanks,
Ray
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