From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755289AbdESPrQ convert rfc822-to-8bit (ORCPT ); Fri, 19 May 2017 11:47:16 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:52004 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752916AbdESPrO (ORCPT ); Fri, 19 May 2017 11:47:14 -0400 From: Ivan Mikhaylov To: Michael Ellerman , Alistair Popple , Matt Porter Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Joel Stanley , Paul Mackerras Subject: Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite Date: Fri, 19 May 2017 18:47:05 +0300 X-Mailer: git-send-email 2.10.1 (Apple Git-78) In-Reply-To: <87wp9d5ekz.fsf@concordia.ellerman.id.au> References: <87wp9d5ekz.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 X-MIMETrack: Itemize by SMTP Server on D06ML001/06/M/IBM(Release 9.0.1FP6HF197 | July 7, 2016) at 19/05/2017 16:47:06, Serialize by Router on D06ML001/06/M/IBM(Release 9.0.1FP6HF197 | July 7, 2016) at 19/05/2017 16:47:06 X-TNEFEvaluated: 1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-TM-AS-GCONF: 00 x-cbid: 17051915-0012-0000-0000-00000533BCFC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17051915-0013-0000-0000-0000188C9291 Message-Id: <20170519154705.10504-1-ivan@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-05-19_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1705190098 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Michael, >> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c >> index 2b33cfa..f75e512 100644 >> --- a/arch/powerpc/kernel/time.c >> +++ b/arch/powerpc/kernel/time.c >> @@ -738,12 +738,28 @@ static int __init get_freq(char *name, int cells, unsigned long *val) >> >> static void start_cpu_decrementer(void) >> { >> + unsigned int tcr; >> #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) >> /* Clear any pending timer interrupts */ >> mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); >> >> +#ifdef CONFIG_FSP2 >> + /* >> + * Prevent a kernel panic caused by unintentionally clearing TCR >> + * watchdog bits. At this point in the kernel boot, the watchdog has >> + * already been enabled by u-boot. The original code's attempt to > > Don't refer to "the original code", as it doesn't exist anymore now that > we've patched it. Just say something like ".. so we must not clear the > watchdog configuration bits". Ok, got it. >That breaks the build for other platforms: > > arch/powerpc/kernel/time.c: In function ‘start_cpu_decrementer’: > arch/powerpc/kernel/time.c:741:15: error: unused variable ‘tcr’ [-Werror=unused-variable] > Oops, didn't notice, my fault. >Or you could possibly just always leave TCR[WP], is there any case where >it would be correct to clear that? > >cheers >>From my point of view it's possible. I've checked docu and on idea it should be possible cause WP is only affecting watchdog ping time. Which in case of '00' is very small, around ~5 ms. Ben also in next message said about get rid of ifdef for FSP2. And now patch looks like this, What do you think Michael, Ben? arch/powerpc/kernel/time.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index bc2e08d..2411c49 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -718,11 +718,22 @@ static int __init get_freq(char *name, int cells, unsigned long *val) static void start_cpu_decrementer(void) { #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) + unsigned int tcr; /* Clear any pending timer interrupts */ mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); - /* Enable decrementer interrupt */ - mtspr(SPRN_TCR, TCR_DIE); + tcr = mfspr(SPRN_TCR); + /* + * At this point in the kernel boot, the watchdog has already + * been enabled by u-boot. If we set it this to '00' it may + * trigger watchdog earlier than needed which will cause + * inattentional kernel panic. In this case we leaving TCR[WP] + * bit setting from uboot/bootstrap. + */ + tcr &= TCR_WP_MASK; /* clear all bits except for TCR[WP] */ + tcr |= TCR_DIE; /* enable decrementer */ + mtspr(SPRN_TCR, tcr); + #endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ } -- 1.7.1