From patchwork Mon May 10 11:07:08 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Walle X-Patchwork-Id: 12247693 X-Patchwork-Delegate: kuba@kernel.org 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 0E052C43461 for ; Mon, 10 May 2021 11:32:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D6F76610A5 for ; Mon, 10 May 2021 11:32:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235327AbhEJLdL (ORCPT ); Mon, 10 May 2021 07:33:11 -0400 Received: from ssl.serverraum.org ([176.9.125.105]:52703 "EHLO ssl.serverraum.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236627AbhEJLIW (ORCPT ); Mon, 10 May 2021 07:08:22 -0400 Received: from mwalle01.fritz.box (unknown [IPv6:2a02:810c:c200:2e91:fa59:71ff:fe9b:b851]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 757B022239; Mon, 10 May 2021 13:07:15 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1620644836; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=UvqLle58hbQrYS8D+Qw3M/VyRDyS9/kql1bKzFA9u7k=; b=fARMSm9TNGEW00ePDePRuLEWD6meuhM4gNJBexH8X5WahVhkjcmFtIsh/DkiZ1PZadJdlT l3/Z/XBwt3yGoJUb3z5w+Uw2QS8BKKV+qPLzxcQb5TNaW/2096auE7k6llCniolwJprYq+ ygS8YDrQqBviVGNwEKsF4vjWMF4yaD4= From: Michael Walle To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Vladimir Oltean , Claudiu Manoil , Alexandre Belloni , UNGLinuxDriver@microchip.com, Andrew Lunn , Vivien Didelot , Florian Fainelli , "David S . Miller" , Jakub Kicinski , Xiaoliang Yang , Michael Walle Subject: [PATCH net] net: dsa: felix: re-enable TAS guard band mode Date: Mon, 10 May 2021 13:07:08 +0200 Message-Id: <20210510110708.11504-1-michael@walle.cc> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-Spam: Yes Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org Commit 316bcffe4479 ("net: dsa: felix: disable always guard band bit for TAS config") disabled the guard band and broke 802.3Qbv compliance. There are two issues here: (1) Without the guard band the end of the scheduling window could be overrun by a frame in transit. (2) Frames that don't fit into a configured window will still be sent. The reason for both issues is that the switch will schedule the _start_ of a frame transmission inside the predefined window without taking the length of the frame into account. Thus, we'll need the guard band which will close the gate early, so that a complete frame can still be sent. Revert the commit and add a note. For a lengthy discussion see [1]. [1] https://lore.kernel.org/netdev/c7618025da6723418c56a54fe4683bd7@walle.cc/ Fixes: 316bcffe4479 ("net: dsa: felix: disable always guard band bit for TAS config") Signed-off-by: Michael Walle Reviewed-by: Vladimir Oltean --- drivers/net/dsa/ocelot/felix_vsc9959.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c index 2473bebe48e6..f966a253d1c7 100644 --- a/drivers/net/dsa/ocelot/felix_vsc9959.c +++ b/drivers/net/dsa/ocelot/felix_vsc9959.c @@ -1227,12 +1227,17 @@ static int vsc9959_qos_port_tas_set(struct ocelot *ocelot, int port, if (taprio->num_entries > VSC9959_TAS_GCL_ENTRY_MAX) return -ERANGE; - /* Set port num and disable ALWAYS_GUARD_BAND_SCH_Q, which means set - * guard band to be implemented for nonschedule queues to schedule - * queues transition. + /* Enable guard band. The switch will schedule frames without taking + * their length into account. Thus we'll always need to enable the + * guard band which reserves the time of a maximum sized frame at the + * end of the time window. + * + * Although the ALWAYS_GUARD_BAND_SCH_Q bit is global for all ports, we + * need to set PORT_NUM, because subsequent writes to PARAM_CFG_REG_n + * operate on the port number. */ - ocelot_rmw(ocelot, - QSYS_TAS_PARAM_CFG_CTRL_PORT_NUM(port), + ocelot_rmw(ocelot, QSYS_TAS_PARAM_CFG_CTRL_PORT_NUM(port) | + QSYS_TAS_PARAM_CFG_CTRL_ALWAYS_GUARD_BAND_SCH_Q, QSYS_TAS_PARAM_CFG_CTRL_PORT_NUM_M | QSYS_TAS_PARAM_CFG_CTRL_ALWAYS_GUARD_BAND_SCH_Q, QSYS_TAS_PARAM_CFG_CTRL);