From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DD44539B4BC; Fri, 17 Jul 2026 12:39:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784291994; cv=none; b=nGdMyq7nkV6O7olAVwNRmJ7a4EWREjT6hv7iYM3uFDNYeXJMqkEaJ9sirBUSQEF1S099zIf60um+hWnbahpkMZL9wEo/Dp0WuAGgFFf+C8/GG5d8esh2dUQLHGL1M0OY7xNi9hoIz3EXFShgHO9JJChYQr958Jzhm7PbRLB/ygo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784291994; c=relaxed/simple; bh=sgNDHJb3RKgnT1vrDMA6ETnGqUQSBLnSbjiP8j2PMj0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=pFb0nhVnpBlfXZaddqfN64V+0CaDX1tU8WKb9RrOOM9ihJTUVUSjim87DFmb44QPngaKcMRalQwEm2ioA5D8x1VSapGfTIjEKoyTksz7kA2xbtG8Gf2Lklo+TRLw5T4JWx0YYeBf9jqf5+NwyE2hfsk4tbNOPBqX9sUhCdzaz1U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=E37kNoqN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="E37kNoqN" Received: by smtp.kernel.org (Postfix) with ESMTPS id B240CC2BCF6; Fri, 17 Jul 2026 12:39:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1784291994; bh=sgNDHJb3RKgnT1vrDMA6ETnGqUQSBLnSbjiP8j2PMj0=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=E37kNoqNBnL9MxC4gniH+1NrHMROWgLd2JLanN89DyStR/C+QhpM2SB3mDqeRUmSk 1ueH+lClVGB7X4yi/TQnYRJQuHdWezgsKHotSd8V3PAuTy0n4ztuS6C68IgRclIlwB Ciyisdi4Iry/cRslIsX+hkersSrumq0zQ9ejhNCXQimMq4nGFCwpEqzMClgZ2S6GbM 9N75EWLdpwwzHGSnHm2vXBVt7RYjHJfVR74MwGNBfJuOcYXWEEwpfuGZavbgSFOYmS xs07Xriy6Ilpy00/31KShvNbSR164AKjnECGTKotPMR9JF77wwiJ25KxFVygSwkQXw Yo3cIK8iF6wBg== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96B6AC44520; Fri, 17 Jul 2026 12:39:54 +0000 (UTC) From: Jean-Baptiste Maneyrol via B4 Relay Date: Fri, 17 Jul 2026 14:39:41 +0200 Subject: [PATCH 2/2] iio: invensense: improve period measurement by using a longer delay Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260717-iio-common-inv-sensors-timestamp-rework-v1-2-d1afee2805cd@tdk.com> References: <20260717-iio-common-inv-sensors-timestamp-rework-v1-0-d1afee2805cd@tdk.com> In-Reply-To: <20260717-iio-common-inv-sensors-timestamp-rework-v1-0-d1afee2805cd@tdk.com> To: Jonathan Cameron , David Lechner , =?utf-8?q?Nuno_S=C3=A1?= , Andy Shevchenko Cc: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Jean-Baptiste Maneyrol X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1784291993; l=4521; i=jean-baptiste.maneyrol@tdk.com; s=20240923; h=from:subject:message-id; bh=QaB1sqyTIlaV5WHBIAd4mGNxiNij+cw0Vv5qDbn6Sr4=; b=aiCdjaLn9gJqnWHa6UH0pXxfZt/qHxBg0e73Luv8nALJmZXVHxaZxUYOMVB9Jwj49buy98D9y IvO6fFf82+iAo4P5SpQXeLHspXm8Wpv0fPtHbFagN2uzhY3C6PP0mo+ X-Developer-Key: i=jean-baptiste.maneyrol@tdk.com; a=ed25519; pk=bRqF1WYk0hR3qrnAithOLXSD0LvSu8DUd+quKLxCicI= X-Endpoint-Received: by B4 Relay for jean-baptiste.maneyrol@tdk.com/20240923 with auth_id=218 X-Original-From: Jean-Baptiste Maneyrol Reply-To: jean-baptiste.maneyrol@tdk.com From: Jean-Baptiste Maneyrol Period measurement can be difficult when using high sampling frequency where the jitter criteria is hard to meet because of the system jitter. This new version is using the delta time between 2 distant interrupts to measure an interval of at least 20ms. 20ms is a good compromise between the mitigation of system jitter and the delay to update period. This way we decorrelate the period measurement from the interrupt timestamps syncing using only the 2 last interrupts. Signed-off-by: Jean-Baptiste Maneyrol --- .../iio/common/inv_sensors/inv_sensors_timestamp.c | 31 +++++++++++++++++----- include/linux/iio/common/inv_sensors_timestamp.h | 6 +++++ 2 files changed, 31 insertions(+), 6 deletions(-) diff --git a/drivers/iio/common/inv_sensors/inv_sensors_timestamp.c b/drivers/iio/common/inv_sensors/inv_sensors_timestamp.c index 2c89e0edc87d..63c1d8a2e19a 100644 --- a/drivers/iio/common/inv_sensors/inv_sensors_timestamp.c +++ b/drivers/iio/common/inv_sensors/inv_sensors_timestamp.c @@ -16,6 +16,9 @@ #define INV_SENSORS_TIMESTAMP_MAX(_val, _jitter) \ (((_val) * (1000 + (_jitter))) / 1000) +/* minimum timestamp delta between 2 interrupts for measuring period (20ms) */ +#define INV_SENSORS_MIN_IT_DELTA (20 * NSEC_PER_MSEC) + /* Add a new value inside an accumulator and update the estimate value */ static void inv_update_acc(struct inv_sensors_timestamp_acc *acc, uint32_t val) { @@ -121,10 +124,13 @@ static uint32_t inv_align_timestamp_it(struct inv_sensors_timestamp *ts, void inv_sensors_timestamp_interrupt(struct inv_sensors_timestamp *ts, size_t sample_nb, int64_t timestamp) { + const int64_t delta_threshold = + INV_SENSORS_TIMESTAMP_MIN(INV_SENSORS_MIN_IT_DELTA, + ts->chip.jitter); struct inv_sensors_timestamp_interval *it; int64_t delta, interval; uint32_t period; - bool valid = false; + bool valid; if (sample_nb == 0) return; @@ -136,16 +142,29 @@ void inv_sensors_timestamp_interrupt(struct inv_sensors_timestamp *ts, ts->timestamp = timestamp - interval; } + /* update delta timestamps and estimated period */ + it = &ts->delta; + ts->delta_counter += sample_nb; + delta = timestamp - it->up; + if (delta >= delta_threshold) { + it->lo = it->up; + it->up = timestamp; + if (it->lo != 0) { + /* compute period: delta time divided by number of samples */ + delta = it->up - it->lo; + period = div_s64(delta, sample_nb); + inv_update_chip_period(ts, period); + } + ts->delta_counter = 0; + } + /* update interrupt timestamp and compute chip and sensor periods */ it = &ts->it; it->lo = it->up; it->up = timestamp; delta = it->up - it->lo; - if (it->lo != 0) { - /* compute period: delta time divided by number of samples */ - period = div_s64(delta, sample_nb); - valid = inv_update_chip_period(ts, period); - } + period = div_s64(delta, sample_nb); + valid = inv_validate_period(ts, period); /* if interrupt interval is valid, sync with interrupt timestamp */ ts->period = valid ? inv_align_timestamp_it(ts, sample_nb) : diff --git a/include/linux/iio/common/inv_sensors_timestamp.h b/include/linux/iio/common/inv_sensors_timestamp.h index 8d506f1e9df2..bc04831f54c4 100644 --- a/include/linux/iio/common/inv_sensors_timestamp.h +++ b/include/linux/iio/common/inv_sensors_timestamp.h @@ -46,6 +46,8 @@ struct inv_sensors_timestamp_acc { * @min_period: minimal acceptable clock period * @max_period: maximal acceptable clock period * @it: interrupts interval timestamps + * @delta: interval timestamps between several interrupts + * @delta_counter: number of data samples in the delta interval * @timestamp: store last timestamp for computing next data timestamp * @mult: current internal period multiplier * @new_mult: new set internal period multiplier (not yet effective) @@ -57,6 +59,8 @@ struct inv_sensors_timestamp { uint32_t min_period; uint32_t max_period; struct inv_sensors_timestamp_interval it; + struct inv_sensors_timestamp_interval delta; + uint32_t delta_counter; int64_t timestamp; uint32_t mult; uint32_t new_mult; @@ -88,6 +92,8 @@ static inline void inv_sensors_timestamp_reset(struct inv_sensors_timestamp *ts) const struct inv_sensors_timestamp_interval interval_init = {0LL, 0LL}; ts->it = interval_init; + ts->delta = interval_init; + ts->delta_counter = 0; ts->timestamp = 0; } -- 2.54.0