From patchwork Fri Mar 30 21:05:11 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bjorn Helgaas X-Patchwork-Id: 10318367 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id AE69C60212 for ; Fri, 30 Mar 2018 21:08:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9D5A328E30 for ; Fri, 30 Mar 2018 21:08:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8F0102A661; Fri, 30 Mar 2018 21:08:41 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 361A128E30 for ; Fri, 30 Mar 2018 21:08:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752947AbeC3VFP (ORCPT ); Fri, 30 Mar 2018 17:05:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:33576 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752941AbeC3VFN (ORCPT ); Fri, 30 Mar 2018 17:05:13 -0400 Received: from localhost (unknown [69.71.5.252]) (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 9FFA821777; Fri, 30 Mar 2018 21:05:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9FFA821777 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=helgaas@kernel.org Subject: [PATCH v5 04/14] PCI: Add pcie_bandwidth_available() to compute bandwidth available to device From: Bjorn Helgaas To: Tal Gilboa Cc: Tariq Toukan , Jacob Keller , Ariel Elior , Ganesh Goudar , Jeff Kirsher , everest-linux-l2@cavium.com, intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Date: Fri, 30 Mar 2018 16:05:11 -0500 Message-ID: <152244391143.135666.12548496808512444463.stgit@bhelgaas-glaptop.roam.corp.google.com> In-Reply-To: <152244269202.135666.3064353823697623332.stgit@bhelgaas-glaptop.roam.corp.google.com> References: <152244269202.135666.3064353823697623332.stgit@bhelgaas-glaptop.roam.corp.google.com> User-Agent: StGit/0.18 MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Tal Gilboa Add pcie_bandwidth_available() to compute the bandwidth available to a device. This may be limited by the device itself or by a slower upstream link leading to the device. The available bandwidth at each link along the path is computed as: link_speed * link_width * (1 - encoding_overhead) The encoding overhead is about 20% for 2.5 and 5.0 GT/s links using 8b/10b encoding, and about 1.5% for 8 GT/s or higher speed links using 128b/130b encoding. Also return the device with the slowest link and the speed and width of that link. Signed-off-by: Tal Gilboa [bhelgaas: changelog, leave pcie_get_minimum_link() alone for now, return bw directly, use pci_upstream_bridge(), check "next_bw <= bw" to find uppermost limiting device, return speed/width of the limiting device] Signed-off-by: Bjorn Helgaas --- drivers/pci/pci.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/pci.h | 3 +++ 2 files changed, 57 insertions(+) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 9ce89e254197..e00d56b12747 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5146,6 +5146,60 @@ int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed, } EXPORT_SYMBOL(pcie_get_minimum_link); +/** + * pcie_bandwidth_available - determine minimum link settings of a PCIe + * device and its bandwidth limitation + * @dev: PCI device to query + * @limiting_dev: storage for device causing the bandwidth limitation + * @speed: storage for speed of limiting device + * @width: storage for width of limiting device + * + * Walk up the PCI device chain and find the point where the minimum + * bandwidth is available. Return the bandwidth available there and (if + * limiting_dev, speed, and width pointers are supplied) information about + * that point. + */ +u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev, + enum pci_bus_speed *speed, + enum pcie_link_width *width) +{ + u16 lnksta; + enum pci_bus_speed next_speed; + enum pcie_link_width next_width; + u32 bw, next_bw; + + *speed = PCI_SPEED_UNKNOWN; + *width = PCIE_LNK_WIDTH_UNKNOWN; + bw = 0; + + while (dev) { + pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta); + + next_speed = pcie_link_speed[lnksta & PCI_EXP_LNKSTA_CLS]; + next_width = (lnksta & PCI_EXP_LNKSTA_NLW) >> + PCI_EXP_LNKSTA_NLW_SHIFT; + + next_bw = next_width * PCIE_SPEED2MBS_ENC(next_speed); + + /* Check if current device limits the total bandwidth */ + if (!bw || next_bw <= bw) { + bw = next_bw; + + if (limiting_dev) + *limiting_dev = dev; + if (speed) + *speed = next_speed; + if (width) + *width = next_width; + } + + dev = pci_upstream_bridge(dev); + } + + return bw; +} +EXPORT_SYMBOL(pcie_bandwidth_available); + /** * pcie_get_speed_cap - query for the PCI device's link speed capability * @dev: PCI device to query diff --git a/include/linux/pci.h b/include/linux/pci.h index 8043a5937ad0..f2bf2b7a66c7 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -1083,6 +1083,9 @@ int pcie_get_mps(struct pci_dev *dev); int pcie_set_mps(struct pci_dev *dev, int mps); int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed, enum pcie_link_width *width); +u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev, + enum pci_bus_speed *speed, + enum pcie_link_width *width); void pcie_flr(struct pci_dev *dev); int __pci_reset_function_locked(struct pci_dev *dev); int pci_reset_function(struct pci_dev *dev);