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Thu, 15 Oct 2026 11:40:14 +0000 Message-ID: Date: Thu, 15 Oct 2026 14:40:12 +0300 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] clocksource/drivers/nxp-stm: Register sched_clock once To: Juhee Kang , Daniel Lezcano , Thomas Gleixner Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, NXP S32 Linux Team , Dustin Black , stable@vger.kernel.org References: <20261015113738.435986-1-juhee.kang@redhat.com> Content-Language: en-GB From: Ghennadi Procopciuc In-Reply-To: <20261015113738.435986-1-juhee.kang@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AS4P192CA0034.EURP192.PROD.OUTLOOK.COM (2603:10a6:20b:658::13) To AMBPR04MB021426.eurprd04.prod.outlook.com (2603:10a6:20b:78c::16) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AMBPR04MB021426:EE_|VI0PR04MB11867:EE_ X-MS-Office365-Filtering-Correlation-Id: 909a761e-1647-4ab4-42d5-08df2ab113eb X-MS-Exchange-SharedMailbox-RoutingAgent-Processed: True X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|23010399003|19092799006|56012099006|11063799006|261009223027099003|260925021311599003|260925022911599003|260925021911599003|10067099003|22082099003|18002099003; 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Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ] > > Each probe updates stm_sched_clock before calling sched_clock_register() > again. The call then subtracts the counter value saved during the > previous registration from the new STM's counter. If the new counter is > smaller, the subtraction wraps and the timestamp jumps forward. > (e.g. from 0.4 to 32.9 seconds below) > > [ 0.403653] sched_clock: 32 bits at 132MHz, resolution 7ns, wraps every 16243448316ns > [ 0.404056] clocksource: timer@40120000: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 14456668980 ns > [ 32.890509] sched_clock: 32 bits at 132MHz, resolution 7ns, wraps every 16243448316ns > [ 32.890882] clocksource: timer@40124000: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 14456668980 ns > > To fix this, register sched_clock once at the end of the first > successful probe. Clocksource and per-CPU clockevent registration > remain unchanged. > > Fixes: cec32ac75827 ("clocksource/drivers/nxp-timer: Add the System Timer Module for the s32gx platforms") > Reported-by: Dustin Black > Signed-off-by: Juhee Kang > Reviewed-by: Ghennadi Procopciuc > --- > Changes in v2: > - add the comment > --- > drivers/clocksource/timer-nxp-stm.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/drivers/clocksource/timer-nxp-stm.c b/drivers/clocksource/timer-nxp-stm.c > index 6fe098a4a33f..23b2d44e4b78 100644 > --- a/drivers/clocksource/timer-nxp-stm.c > +++ b/drivers/clocksource/timer-nxp-stm.c > @@ -211,10 +211,6 @@ static int nxp_stm_clocksource_init(struct device *dev, struct stm_timer *stm_ti > if (ret) > return ret; > > - stm_sched_clock = stm_timer; > - > - sched_clock_register(nxp_stm_read_sched_clock, 32, stm_timer->rate); > - > dev_dbg(dev, "Registered clocksource %s\n", name); > > return 0; > @@ -473,6 +469,15 @@ static int nxp_stm_timer_probe(struct platform_device *pdev) > return ret; > } > > + /* > + * STM counters run independently at the same rate. Use the first > + * probed instance for sched_clock to avoid timestamp jumps. > + */ > + if (!stm_sched_clock) { > + stm_sched_clock = stm_timer; > + sched_clock_register(nxp_stm_read_sched_clock, 32, stm_timer->rate); > + } > + > return 0; > } > > -- > 2.55.0 Thank you for addressing this issue! Tested-by: Ghennadi Procopciuc -- Regards, Ghennadi