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 A2EDBEB64DD for ; Tue, 27 Jun 2023 10:48:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231304AbjF0KsV (ORCPT ); Tue, 27 Jun 2023 06:48:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54176 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230310AbjF0KsS (ORCPT ); Tue, 27 Jun 2023 06:48:18 -0400 Received: from mail-pf1-f176.google.com (mail-pf1-f176.google.com [209.85.210.176]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB34F10D8; Tue, 27 Jun 2023 03:48:17 -0700 (PDT) Received: by mail-pf1-f176.google.com with SMTP id d2e1a72fcca58-66c729f5618so2867715b3a.1; Tue, 27 Jun 2023 03:48:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687862897; x=1690454897; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=N8kR5N8k1cATdBJ+KhZdRci8FZk5P5nCz0LfFdh3fX4=; b=NWDaF18hqry3cIREP7vfFyG9g6N0hWt0Eiae0MFkQ+IjDTLgpS4w6ViKPrKKS7w4Ra 2kE3s31dAIUSJn7py54r/bPGUH4uLQ6bs4hStGMDVIi0SsPcFmxrJZ3SBeijQuF03Lhx 04IaY4LAgzxq63Z3TFwRsypIjlksV0zN8loBAimA3xTosGHQ0hDRJYGhVElY9xVNlJ22 Fl/r0fgi9g3aZRJzD/tGKG4nkM8DpH7qx3UOeqBRVJ9WSlYM06jzOROTNUfrtQmA1o63 ok4s+Q7q498Pa637JdL5XsDFdmAmvkYJRUM38RP2Fu1LoSiworitELQdCYhoXbd/4IXD K28w== X-Gm-Message-State: AC+VfDwCRZAPHpfhLh3Xg9rteit7DhgDdQFX+u0VKLm+eyLPWz+8//Cj TdkC2vDVk5RmaZFnmgo6vas= X-Google-Smtp-Source: ACHHUZ5tgtCulcm7hoVplGcarYJQ0IMFJCwGAz7GA7wJbXixNt/NX0oiVwmcSOn6w0VAWhJilFBySw== X-Received: by 2002:a05:6a00:c86:b0:676:76ea:e992 with SMTP id a6-20020a056a000c8600b0067676eae992mr6523213pfv.5.1687862897025; Tue, 27 Jun 2023 03:48:17 -0700 (PDT) Received: from localhost (fpd11144dd.ap.nuro.jp. [209.17.68.221]) by smtp.gmail.com with ESMTPSA id d25-20020aa78159000000b0064378c52398sm5184966pfn.25.2023.06.27.03.48.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jun 2023 03:48:15 -0700 (PDT) Date: Tue, 27 Jun 2023 19:48:14 +0900 From: Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= To: Vidya Sagar Cc: lpieralisi@kernel.org, robh@kernel.org, bhelgaas@google.com, thierry.reding@gmail.com, jonathanh@nvidia.com, Sergey.Semin@baikalelectronics.ru, linux-pci@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, kthota@nvidia.com, mmaddireddy@nvidia.com, sagar.tv@gmail.com Subject: Re: [PATCH V3] Revert "PCI: tegra194: Enable support for 256 Byte payload" Message-ID: <20230627104814.GA3676313@rocinante> References: <20230619014218.1970846-1-vidyas@nvidia.com> <20230619102604.3735001-1-vidyas@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230619102604.3735001-1-vidyas@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, > This reverts commit 4fb8e46c1bc4 ("PCI: tegra194: Enable > support for 256 Byte payload"). > > Consider a PCIe hierarchy with a PCIe switch and a device connected > downstream of the switch that has support for MPS which is the minimum in > the hierarchy, and root port programmed with an MPS in its DevCtl register > that is greater than the minimum. In this scenario, the default bus > configuration of the kernel i.e. "PCIE_BUS_DEFAULT" doesn't configure the > MPS settings in the hierarchy correctly resulting in the device with > support for minimum MPS in the hierarchy receiving the TLPs of size more > than that. Although this can be addressed by appending "pci=pcie_bus_safe" > to the kernel command line, it doesn't seem to be a good idea to always > have this commandline argument even for the basic functionality to work. > > Reverting commit 4fb8e46c1bc4 ("PCI: tegra194: Enable support for 256 > Byte payload") avoids this requirement and ensures that the basic > functionality of the devices irrespective of the hierarchy and the MPS of > the devices in the hierarchy. > > To reap the benefits of having support for higher MPS, optionally, one can > always append the kernel command line with "pci=pcie_bus_perf". Applied to controller/tegra194, thank you! [1/1] Revert "PCI: tegra194: Enable support for 256 Byte payload" https://git.kernel.org/pci/pci/c/606295f16360 Krzysztof