From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 969F247C106; Sat, 12 Sep 2026 16:32:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789230754; cv=none; b=R7S6t7ldZRhdHOUHOJPOXesnQf32Kcq+uMVxvRdNMPV8LAf3Jyx07I/tufxEKNlm/Dx2jKq0mc2BcAC4t06MTfoK2YGyDCCb2nK0gc+WOvLzMOHoa1WSYCvQnfpP/Cyxq8h2QUJezctFyCrwhP4K1+4BH2t71RDQBVir9HJYPyI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789230754; c=relaxed/simple; bh=I4IHgL5BQjU3R4Rb95R5aD6M4GXqd5iLPYVx+bWAFoo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Egs6x5bqo9i+aGDkGpLcv581jyQp5VbeDUzn4A8a5B+ZqhDPuPncLwH6kzf0iNWFUgs99WRpkqkGgLRrBZ0BwFyYgyAEGcmuSPar+F1Nsku8UaUDxVNc8fmnTeLcBzEid9pXuSS9SC1L/+4usXlLmeXNfNqfrI5snW84pp5j+7M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0FbFMkFM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="0FbFMkFM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 990291F000FF; Sat, 12 Sep 2026 16:32:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789230753; bh=MJUVpdkIb/XFPVDPZnt1T7eRdrmWRkZdt8M7C/2VlVo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=0FbFMkFMGVacHILNYmSHkocag+7WjMtGkAYSd1L6WipsmIV/MRrr6OF8juBKRAx/g fyxK37oMVbQW214PZpOxMOceAc31sqdbZH06EqS1Vw1ZwTOa/PxoOa1N49TsruIh9B +Dp1258AgQVfUVUdch3PrGiF35pbS8wDnL9Xhd0c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Michael Byczkowski , Calvin Owens , Sebastian Andrzej Siewior , Rodolfo Giometti , Andrew Morton , Sasha Levin Subject: [PATCH 6.1 0858/1191] pps: pps-gpio: split IRQ handler into hardirq timestamper + threaded handler Date: Sat, 12 Sep 2026 08:59:46 +0200 Message-ID: <20260912065607.523046407@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065548.086904252@linuxfoundation.org> References: <20260912065548.086904252@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michael Byczkowski [ Upstream commit 93781560b2fdd26fa8499d64db8a95a07e1dc902 ] Split the pps-gpio interrupt handler into a primary (hardirq) handler that captures the PPS timestamp at interrupt entry, and a threaded handler that processes the event. This produces the same two-part handler structure on both PREEMPT_RT and non-RT kernels. On non-RT kernels the threaded portion runs immediately after the primary, with no behavioral change compared to the previous single-handler implementation. On PREEMPT_RT, where interrupt handlers are force-threaded by default, the previous single-handler implementation captured the timestamp inside the threaded portion, after IRQ-thread scheduling delay. With the split, the timestamp is captured in true hardirq context as it is on non-RT kernels, eliminating a significant source of PPS jitter on RT systems. Link: https://lore.kernel.org/2e32729029fbf6977ecf04665eb00f2efd3e2c17.1780359378.git.calvin@wbinvd.org Signed-off-by: Michael Byczkowski Signed-off-by: Calvin Owens Reviewed-by: Sebastian Andrzej Siewior Tested-by: Michael Byczkowski Tested-by: Calvin Owens Acked-by: Rodolfo Giometti Signed-off-by: Andrew Morton Stable-dep-of: b899e0279f90 ("pps-gpio: remove dead capture_clear code") Signed-off-by: Sasha Levin --- drivers/pps/clients/pps-gpio.c | 37 +++++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 12 deletions(-) diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c index dbe598d092099..d21fc4bf0e3df 100644 --- a/drivers/pps/clients/pps-gpio.c +++ b/drivers/pps/clients/pps-gpio.c @@ -35,33 +35,44 @@ struct pps_gpio_device_data { bool capture_clear; unsigned int echo_active_ms; /* PPS echo active duration */ unsigned long echo_timeout; /* timer timeout value in jiffies */ + struct pps_event_time ts; /* timestamp captured in hardirq */ }; /* * Report the PPS event */ -static irqreturn_t pps_gpio_irq_handler(int irq, void *data) +/* + * Primary hardirq handler -- runs in hardirq context even on PREEMPT_RT. + * Only captures the timestamp; all other work is deferred to the thread. + */ +static irqreturn_t pps_gpio_irq_hardirq(int irq, void *data) { - const struct pps_gpio_device_data *info; - struct pps_event_time ts; - int rising_edge; + struct pps_gpio_device_data *info = data; + + pps_get_ts(&info->ts); - /* Get the time stamp first */ - pps_get_ts(&ts); + return IRQ_WAKE_THREAD; +} - info = data; +/* + * Threaded handler -- processes the PPS event using the timestamp + * captured in hardirq context above. + */ +static irqreturn_t pps_gpio_irq_thread(int irq, void *data) +{ + struct pps_gpio_device_data *info = data; + int rising_edge; - /* Small trick to bypass the check on edge's direction when capture_clear is unset */ rising_edge = info->capture_clear ? gpiod_get_value(info->gpio_pin) : !info->assert_falling_edge; if ((rising_edge && !info->assert_falling_edge) || (!rising_edge && info->assert_falling_edge)) - pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data); + pps_event(info->pps, &info->ts, PPS_CAPTUREASSERT, data); else if (info->capture_clear && ((rising_edge && info->assert_falling_edge) || (!rising_edge && !info->assert_falling_edge))) - pps_event(info->pps, &ts, PPS_CAPTURECLEAR, data); + pps_event(info->pps, &info->ts, PPS_CAPTURECLEAR, data); else dev_warn_ratelimited(&info->pps->dev, "IRQ did not trigger any PPS event\n"); @@ -210,8 +221,10 @@ static int pps_gpio_probe(struct platform_device *pdev) } /* register IRQ interrupt handler */ - ret = request_irq(data->irq, pps_gpio_irq_handler, - get_irqf_trigger_flags(data), data->info.name, data); + ret = request_threaded_irq(data->irq, + pps_gpio_irq_hardirq, pps_gpio_irq_thread, + get_irqf_trigger_flags(data) | IRQF_ONESHOT, + data->info.name, data); if (ret) { pps_unregister_source(data->pps); dev_err(dev, "failed to acquire IRQ %d\n", data->irq); -- 2.53.0