From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BDF1EC56202 for ; Tue, 17 Nov 2020 13:56:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 62D95208B8 for ; Tue, 17 Nov 2020 13:56:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="hbzseiJG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730353AbgKQNze (ORCPT ); Tue, 17 Nov 2020 08:55:34 -0500 Received: from mail.kernel.org ([198.145.29.99]:58662 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730953AbgKQNXv (ORCPT ); Tue, 17 Nov 2020 08:23:51 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2E3C62463D; Tue, 17 Nov 2020 13:23:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605619429; bh=alJIKup29P0H0eTaK2JJmRE8/AWK71R5Q9LuzCjWP64=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hbzseiJGnzaZTflNMcsK2Dt17lOSaoIrHjByKa+IsJW1GnrTvYwM2kHQVB7PfA2KS 9S0h6XabaalGG+g/50Iz4H5wL8YoYW75CzTUDL+4Jvj59TlHUoeFnUGoq5ihsIZenn 0nUiDYrRxpmbbN4J6/bVFf5nCvVQQmuQLifVLhdU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Fabian Inostroza , Stephane Grosjean , Marc Kleine-Budde , Sasha Levin Subject: [PATCH 5.4 035/151] can: peak_usb: peak_usb_get_ts_time(): fix timestamp wrapping Date: Tue, 17 Nov 2020 14:04:25 +0100 Message-Id: <20201117122123.133740275@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201117122121.381905960@linuxfoundation.org> References: <20201117122121.381905960@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Stephane Grosjean [ Upstream commit ecc7b4187dd388549544195fb13a11b4ea8e6a84 ] Fabian Inostroza has discovered a potential problem in the hardware timestamp reporting from the PCAN-USB USB CAN interface (only), related to the fact that a timestamp of an event may precede the timestamp used for synchronization when both records are part of the same USB packet. However, this case was used to detect the wrapping of the time counter. This patch details and fixes the two identified cases where this problem can occur. Reported-by: Fabian Inostroza Signed-off-by: Stephane Grosjean Link: https://lore.kernel.org/r/20201014085631.15128-1-s.grosjean@peak-system.com Fixes: bb4785551f64 ("can: usb: PEAK-System Technik USB adapters driver core") Signed-off-by: Marc Kleine-Budde Signed-off-by: Sasha Levin --- drivers/net/can/usb/peak_usb/pcan_usb_core.c | 51 ++++++++++++++++++-- 1 file changed, 46 insertions(+), 5 deletions(-) diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_core.c b/drivers/net/can/usb/peak_usb/pcan_usb_core.c index 0b7766b715fd2..c844c6abe5fcd 100644 --- a/drivers/net/can/usb/peak_usb/pcan_usb_core.c +++ b/drivers/net/can/usb/peak_usb/pcan_usb_core.c @@ -130,14 +130,55 @@ void peak_usb_get_ts_time(struct peak_time_ref *time_ref, u32 ts, ktime_t *time) /* protect from getting time before setting now */ if (ktime_to_ns(time_ref->tv_host)) { u64 delta_us; + s64 delta_ts = 0; + + /* General case: dev_ts_1 < dev_ts_2 < ts, with: + * + * - dev_ts_1 = previous sync timestamp + * - dev_ts_2 = last sync timestamp + * - ts = event timestamp + * - ts_period = known sync period (theoretical) + * ~ dev_ts2 - dev_ts1 + * *but*: + * + * - time counters wrap (see adapter->ts_used_bits) + * - sometimes, dev_ts_1 < ts < dev_ts2 + * + * "normal" case (sync time counters increase): + * must take into account case when ts wraps (tsw) + * + * < ts_period > < > + * | | | + * ---+--------+----+-------0-+--+--> + * ts_dev_1 | ts_dev_2 | + * ts tsw + */ + if (time_ref->ts_dev_1 < time_ref->ts_dev_2) { + /* case when event time (tsw) wraps */ + if (ts < time_ref->ts_dev_1) + delta_ts = 1 << time_ref->adapter->ts_used_bits; + + /* Otherwise, sync time counter (ts_dev_2) has wrapped: + * handle case when event time (tsn) hasn't. + * + * < ts_period > < > + * | | | + * ---+--------+--0-+---------+--+--> + * ts_dev_1 | ts_dev_2 | + * tsn ts + */ + } else if (time_ref->ts_dev_1 < ts) { + delta_ts = -(1 << time_ref->adapter->ts_used_bits); + } - delta_us = ts - time_ref->ts_dev_2; - if (ts < time_ref->ts_dev_2) - delta_us &= (1 << time_ref->adapter->ts_used_bits) - 1; + /* add delay between last sync and event timestamps */ + delta_ts += (signed int)(ts - time_ref->ts_dev_2); - delta_us += time_ref->ts_total; + /* add time from beginning to last sync */ + delta_ts += time_ref->ts_total; - delta_us *= time_ref->adapter->us_per_ts_scale; + /* convert ticks number into microseconds */ + delta_us = delta_ts * time_ref->adapter->us_per_ts_scale; delta_us >>= time_ref->adapter->us_per_ts_shift; *time = ktime_add_us(time_ref->tv_host_0, delta_us); -- 2.27.0