From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424660AbcFMWfg (ORCPT ); Mon, 13 Jun 2016 18:35:36 -0400 Received: from mail-pf0-f173.google.com ([209.85.192.173]:34949 "EHLO mail-pf0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423549AbcFMWev (ORCPT ); Mon, 13 Jun 2016 18:34:51 -0400 Subject: Re: [PATCH] clocksource: kona: avoid bogus warning To: Arnd Bergmann , Daniel Lezcano , Thomas Gleixner References: <1465850461-3533361-1-git-send-email-arnd@arndb.de> Cc: Florian Fainelli , Ray Jui , Scott Branden , Viresh Kumar , bcm-kernel-feedback-list@broadcom.com, linux-kernel@vger.kernel.org From: Ray Jui Message-ID: <555867a6-6b38-691e-a1c4-1168dbf61dca@broadcom.com> Date: Mon, 13 Jun 2016 15:34:38 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2 MIME-Version: 1.0 In-Reply-To: <1465850461-3533361-1-git-send-email-arnd@arndb.de> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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