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Tue, 13 Oct 2026 11:01:03 +0000 Message-ID: <54e1f3fb-136b-45e4-9ca9-6c73383851ab@oss.nxp.com> Date: Tue, 13 Oct 2026 14:01:02 +0300 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] 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: <20260913133645.1102997-1-juhee.kang@redhat.com> Content-Language: en-GB From: Ghennadi Procopciuc In-Reply-To: <20260913133645.1102997-1-juhee.kang@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AM9P250CA0019.EURP250.PROD.OUTLOOK.COM (2603:10a6:20b:21c::24) 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_|AMDPR04MB11607:EE_ X-MS-Office365-Filtering-Correlation-Id: 186615d7-5e05-4b6a-f43d-08df291945be 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|19092799006|23010399003|1800799024|366016|376014|22082099003|260925021911599003|260925022911599003|260925021311599003|10067099003|18002099003|11063799006|261009223027099003|56012099006; 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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 > --- > drivers/clocksource/timer-nxp-stm.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/clocksource/timer-nxp-stm.c b/drivers/clocksource/timer-nxp-stm.c > index 6fe098a4a33f..7572cd20732f 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 +469,11 @@ static int nxp_stm_timer_probe(struct platform_device *pdev) > return ret; > } > > + if (!stm_sched_clock) { > + stm_sched_clock = stm_timer; > + sched_clock_register(nxp_stm_read_sched_clock, 32, stm_timer->rate); > + } > + > return 0; > } > One optional nit: a short comment above the block would help future readers understand why it runs only once, e.g.: /* * The STM instances are independent counters running at the same * rate. Only one of them can back sched_clock, use the first one * probed. */ With or without it: Reviewed-by: Ghennadi Procopciuc -- Regards, Ghennadi