From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753852AbcIHGWu (ORCPT ); Thu, 8 Sep 2016 02:22:50 -0400 Received: from webbox1416.server-home.net ([77.236.96.61]:43089 "EHLO webbox1416.server-home.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752638AbcIHGWt (ORCPT ); Thu, 8 Sep 2016 02:22:49 -0400 From: Alexander Stein To: linux-kernel@vger.kernel.org Cc: Meng Yi , daniel.lezcano@linaro.org, tglx@linutronix.de Subject: Re: [PATCH] clocksource/fsl: Fix errata A-007728 for flextimer Date: Thu, 08 Sep 2016 08:22:39 +0200 Message-ID: <1977031.jHqNsaRUgG@ws-stein> User-Agent: KMail/4.14.10 (Linux/4.7.2-gentoo; KDE/4.14.20; x86_64; ; ) In-Reply-To: <1473300295-32574-1-git-send-email-meng.yi@nxp.com> References: <1473300295-32574-1-git-send-email-meng.yi@nxp.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 08 September 2016 10:04:55, Meng Yi wrote: > If the FTM counter reaches the FTM_MOD value between the reading of the > TOF bit and the writing of 0 to the TOF bit, the process of clearing the > TOF bit does not work as expected when FTMx_CONF[NUMTOF] != 0 and the > current TOF count is less than FTMx_CONF[NUMTOF]. If the above condition > is met, the TOF bit remains set. If the TOF interrupt is enabled > (FTMx_SC[TOIE] = 1), the TOF interrupt also remains asserted. > > Above is the errata discription > > The workaround is clearing TOF bit until it is cleaned(FTM counter doesn't > always reache the FTM_MOD anyway),which may cost some cycles. > > Signed-off-by: Meng Yi > --- > drivers/clocksource/fsl_ftm_timer.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/drivers/clocksource/fsl_ftm_timer.c > b/drivers/clocksource/fsl_ftm_timer.c index 738515b..ade26e5 100644 > --- a/drivers/clocksource/fsl_ftm_timer.c > +++ b/drivers/clocksource/fsl_ftm_timer.c > @@ -83,11 +83,10 @@ static inline void ftm_counter_disable(void __iomem > *base) > > static inline void ftm_irq_acknowledge(void __iomem *base) > { > - u32 val; > - > - val = ftm_readl(base + FTM_SC); > - val &= ~FTM_SC_TOF; > - ftm_writel(val, base + FTM_SC); > + /*read and clean the FTM_SC_TOF bit until its cleared*/ > + while (FTM_SC_TOF & ftm_readl(base + FTM_SC)) > + ftm_writel(ftm_readl(base + FTM_SC) & (~FTM_SC_TOF), > + base + FTM_SC); > } So you are essentially polling hardware in interrupt context. Please add a sensible timeout to abort this loop in case of defective hardware, and maybe disable the interrupt in that case. Best regards, Alexander