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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57500C0015E for ; Tue, 1 Aug 2023 09:43:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233341AbjHAJnl (ORCPT ); Tue, 1 Aug 2023 05:43:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233339AbjHAJnX (ORCPT ); Tue, 1 Aug 2023 05:43:23 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 284ED2D58 for ; Tue, 1 Aug 2023 02:41:06 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id DB78161518 for ; Tue, 1 Aug 2023 09:41:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E62B3C433C8; Tue, 1 Aug 2023 09:40:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1690882860; bh=2rcrRBE08LwPqjx5kyilMWeMDbOFem841Tub+vFgjqw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ASWHZWmraTTlogm8xcumff/CgOAvwNOi1C2GW6p74wurqdqfKJy23g9F+P2WonqP4 +mJ8SxWdzYf60Verh+qVI9kei4ZpiCW2I+hW5lRTCANzi0owQ4AaCFxZ7Rk8HtKjJG Www7qri1zTJJ6T3P5dH7G011o7yFaGjny8vgmDyg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Lukas Wunner , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , Bjorn Helgaas , Sasha Levin Subject: [PATCH 6.4 028/239] PCI/ASPM: Avoid link retraining race Date: Tue, 1 Aug 2023 11:18:12 +0200 Message-ID: <20230801091926.645388350@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230801091925.659598007@linuxfoundation.org> References: <20230801091925.659598007@linuxfoundation.org> User-Agent: quilt/0.67 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: Ilpo Järvinen [ Upstream commit e7e39756363ad5bd83ddeae1063193d0f13870fd ] PCIe r6.0.1, sec 7.5.3.7, recommends setting the link control parameters, then waiting for the Link Training bit to be clear before setting the Retrain Link bit. This avoids a race where the LTSSM may not use the updated parameters if it is already in the midst of link training because of other normal link activity. Wait for the Link Training bit to be clear before toggling the Retrain Link bit to ensure that the LTSSM uses the updated link control parameters. [bhelgaas: commit log, return 0 (success)/-ETIMEDOUT instead of bool for both pcie_wait_for_retrain() and the existing pcie_retrain_link()] Suggested-by: Lukas Wunner Fixes: 7d715a6c1ae5 ("PCI: add PCI Express ASPM support") Link: https://lore.kernel.org/r/20230502083923.34562-1-ilpo.jarvinen@linux.intel.com Signed-off-by: Ilpo Järvinen Signed-off-by: Bjorn Helgaas Reviewed-by: Lukas Wunner Cc: stable@vger.kernel.org Signed-off-by: Sasha Levin --- drivers/pci/pcie/aspm.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index 517f834ac93ef..998e26de2ad76 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -213,8 +213,19 @@ static int pcie_wait_for_retrain(struct pci_dev *pdev) static int pcie_retrain_link(struct pcie_link_state *link) { struct pci_dev *parent = link->pdev; + int rc; u16 reg16; + /* + * Ensure the updated LNKCTL parameters are used during link + * training by checking that there is no ongoing link training to + * avoid LTSSM race as recommended in Implementation Note at the + * end of PCIe r6.0.1 sec 7.5.3.7. + */ + rc = pcie_wait_for_retrain(parent); + if (rc) + return rc; + pcie_capability_read_word(parent, PCI_EXP_LNKCTL, ®16); reg16 |= PCI_EXP_LNKCTL_RL; pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16); -- 2.39.2