Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754766AbcKCVwc (ORCPT ); Thu, 3 Nov 2016 17:52:32 -0400 Received: from mail-yw0-f172.google.com ([209.85.161.172]:34357 "EHLO mail-yw0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751562AbcKCVwa (ORCPT ); Thu, 3 Nov 2016 17:52:30 -0400 Date: Thu, 3 Nov 2016 22:52:21 +0100 From: Daniel Lezcano To: Vineet Gupta Cc: Noam Camus , tglx@linutronix.de, linux-snps-arc@lists.infradead.org, linux-kernel@vger.kernel.org, Alexey.Brodkin@synopsys.com, stable@vger.kernel.org Subject: Re: [PATCH v2 01/10] ARC: timer: rtc: implement read loop in "C" vs. inline asm Message-ID: <20161103215221.GM1859@mai> References: <1478208701-30923-1-git-send-email-vgupta@synopsys.com> <1478208701-30923-2-git-send-email-vgupta@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1478208701-30923-2-git-send-email-vgupta@synopsys.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1600 Lines: 49 On Thu, Nov 03, 2016 at 02:31:32PM -0700, Vineet Gupta wrote: > The current code doesn't even compile .... Give a better description in the log, especially if this patch is supposed to go to stable@ > CC: stable@vger.kernel.org > Signed-off-by: Vineet Gupta > --- > arch/arc/kernel/time.c | 19 +++++++++++-------- > 1 file changed, 11 insertions(+), 8 deletions(-) > > diff --git a/arch/arc/kernel/time.c b/arch/arc/kernel/time.c > index f927b8dc6edd..1a117b999c0c 100644 > --- a/arch/arc/kernel/time.c > +++ b/arch/arc/kernel/time.c > @@ -152,14 +152,17 @@ static cycle_t arc_read_rtc(struct clocksource *cs) > cycle_t full; > } stamp; > > - > - __asm__ __volatile( > - "1: \n" > - " lr %0, [AUX_RTC_LOW] \n" > - " lr %1, [AUX_RTC_HIGH] \n" > - " lr %2, [AUX_RTC_CTRL] \n" > - " bbit0.nt %2, 31, 1b \n" > - : "=r" (stamp.low), "=r" (stamp.high), "=r" (status)); > + /* > + * hardware has an internal state machine which tracks readout of > + * low/high and updates the CTRL.status if > + * - interrupt/exception taken between the two reads > + * - high increments after low has been read > + */ > + do { > + stamp.low = read_aux_reg(AUX_RTC_LOW); > + stamp.high = read_aux_reg(AUX_RTC_HIGH); > + status = read_aux_reg(AUX_RTC_CTRL); > + } while (!(status & _BITUL(31))); Is the condition correct ? If I refer to your previous answer, the bit will be set for status if the counter wrapped up. So in this case, we won't exit the loop until we wrap up, no ? > return stamp.full; > } > -- > 2.7.4 >