From patchwork Mon Jun 14 12:38:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vladimir Oltean X-Patchwork-Id: 460144 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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, 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 8189AC2B9F4 for ; Mon, 14 Jun 2021 12:39:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AF8161208 for ; Mon, 14 Jun 2021 12:39:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233397AbhFNMlh (ORCPT ); Mon, 14 Jun 2021 08:41:37 -0400 Received: from mail-ed1-f44.google.com ([209.85.208.44]:37746 "EHLO mail-ed1-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232775AbhFNMlf (ORCPT ); Mon, 14 Jun 2021 08:41:35 -0400 Received: by mail-ed1-f44.google.com with SMTP id b11so46297254edy.4 for ; Mon, 14 Jun 2021 05:39:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=hgFkwjcJJLaBU8nE16Qln3qRxVwMomFvhqvRMqMhxus=; b=OCcTvZHPcXTl2AJYDO1QFoNIs47QkqawY2WsLpMbZobgWz1IkqvuQEfpwPxq9XtuxV uil26lz823dpwLSdSFFtsWhVyfX7uvXZnJHvi6QEoO3Wnx5wqMhiV2XYvnmwCH6fkEQA Rot49P1/pmdI/ATKXmSXddAuZQ6PtLAHTHuBFwBqwwIB/D8N2xZNTQUT/c+SnUSA+axc XPzdOnngC7heIbVenSdDpZK3fTDDrb3gclAFaQVgT4/XeAFdV9FTLDAfmxue9RW4SsuF WL9w825v4yZ778qEYLpEtTRWEWjJ+xyDwcx2asjofV/LKQ6jPSSwznHcICXJJF/g2/u+ MFnQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=hgFkwjcJJLaBU8nE16Qln3qRxVwMomFvhqvRMqMhxus=; b=V9UMVbwGmBWz6j5xQOq22kGNSNv7f57cxzSPxJN8/T7iZNSDSpvv4opInCe5GOSOOE BShP/7tFnyKUIub86D/0BMUZtUHLIuaxWNMEmuBBh6YqpDvWAJbDtwEhnPK9hyd/yMCi tNiwoAdYgB10TsJ7m7a3podU/5rCX8r1qUCGTOXY5cdxLM1oF2P7mZPA3xjsUgaABH3v FvRTt3+RYqJ1N0aTAbnDua0HptfpQca/tcdcDpsu/rpYVIySKHrJNavKa9BK0/YS847V l3PPqeJHm6lz/ErljCgbW48JC+oMDBOffzMRnP3uhWxd0p2AxazeKwOuR8hN0JWKGYh/ lMdQ== X-Gm-Message-State: AOAM530FF+oRsSR9TQXbIe2LdKxkG3NN1S0ajre5svuPJLXD9vyYlklZ uyKLfWzcTJuab4OD5LAtyGs= X-Google-Smtp-Source: ABdhPJxFMG6f3Z2+GzabkVyxw4VJ2lLHLZe9Kju99XOI6Hwte4u8nWkaB4fobXTkSEqEh90G5LyKbw== X-Received: by 2002:a05:6402:31f3:: with SMTP id dy19mr16673100edb.153.1623674311770; Mon, 14 Jun 2021 05:38:31 -0700 (PDT) Received: from localhost.localdomain ([188.26.224.68]) by smtp.gmail.com with ESMTPSA id f6sm7157965eja.108.2021.06.14.05.38.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Jun 2021 05:38:31 -0700 (PDT) From: Vladimir Oltean To: Jakub Kicinski , "David S. Miller" , netdev@vger.kernel.org Cc: Florian Fainelli , Andrew Lunn , Heiner Kallweit , Russell King , Radu Pirea , Vladimir Oltean , Richard Cochran Subject: [PATCH v2 net-next 2/3] net: phy: nxp-c45-tja11xx: fix potential RX timestamp wraparound Date: Mon, 14 Jun 2021 15:38:14 +0300 Message-Id: <20210614123815.443467-3-olteanv@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210614123815.443467-1-olteanv@gmail.com> References: <20210614123815.443467-1-olteanv@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Vladimir Oltean The reconstruction procedure for partial timestamps reads the current PTP time and fills in the low 2 bits of the second portion, as well as the nanoseconds portion, from the actual hardware packet timestamp. Critically, the reconstruction procedure works because it assumes that the current PTP time is strictly larger than the hardware timestamp was: it detects a 2-bit wraparound of the 'seconds' portion by checking whether the 'seconds' portion of the partial hardware timestamp is larger than the 'seconds' portion of the current time. That can only happen if the hardware timestamp was captured by the PHY during the last phase of a 'modulo 4 seconds' interval, and the current PTP time was read by the driver during the initial phase of the next 'modulo 4 seconds' interval. The partial RX timestamps are added to priv->rx_queue in nxp_c45_rxtstamp() and they are processed potentially in parallel by the aux worker thread in nxp_c45_do_aux_work(). This means that it is possible for nxp_c45_do_aux_work() to process more than one RX timestamp during the same schedule. There is one premature optimization that will cause issues: for RX timestamping, the driver reads the current time only once, and it uses that to reconstruct all PTP RX timestamps in the queue. For the second and later timestamps, this will be an issue if we are processing two RX timestamps which are to the left and to the right, respectively, of a 4-bit wraparound of the 'seconds' portion of the PTP time, and the current PTP time is also pre-wraparound. 0.000000000 4.000000000 8.000000000 12.000000000 |..................|..................|..................|............> ^ ^ ^ ^ time | | | | | | | process hwts 1 and hwts 2 | | | | | hwts 2 | | | read current PTP time | hwts 1 What will happen in that case is that hwts 2 (post-wraparound) will use a stale current PTP time that is pre-wraparound. But nxp_c45_reconstruct_ts will not detect this condition, because it is not coded up for it, so it will reconstruct hwts 2 with a current time from the previous 4 second interval (i.e. 0.something instead of 4.something). This is solvable by making sure that the full 64-bit current time is always read after the PHY has taken the partial RX timestamp. We do this by reading the current PTP time for every timestamp in the RX queue. Fixes: 514def5dd339 ("phy: nxp-c45-tja11xx: add timestamping support") Cc: Richard Cochran Signed-off-by: Vladimir Oltean --- v1->v2: none drivers/net/phy/nxp-c45-tja11xx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/phy/nxp-c45-tja11xx.c b/drivers/net/phy/nxp-c45-tja11xx.c index 902fe1aa7782..118b393b1cbb 100644 --- a/drivers/net/phy/nxp-c45-tja11xx.c +++ b/drivers/net/phy/nxp-c45-tja11xx.c @@ -427,8 +427,8 @@ static long nxp_c45_do_aux_work(struct ptp_clock_info *ptp) nxp_c45_process_txts(priv, &hwts); } - nxp_c45_ptp_gettimex64(&priv->caps, &ts, NULL); while ((skb = skb_dequeue(&priv->rx_queue)) != NULL) { + nxp_c45_ptp_gettimex64(&priv->caps, &ts, NULL); ts_raw = __be32_to_cpu(NXP_C45_SKB_CB(skb)->header->reserved2); hwts.sec = ts_raw >> 30; hwts.nsec = ts_raw & GENMASK(29, 0);