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 X-Spam-Level: X-Spam-Status: No, score=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 9FC6DC433E9 for ; Tue, 2 Mar 2021 07:09:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5B1D664DE8 for ; Tue, 2 Mar 2021 07:09:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243244AbhCBDpg (ORCPT ); Mon, 1 Mar 2021 22:45:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:56568 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243938AbhCAUxk (ORCPT ); Mon, 1 Mar 2021 15:53:40 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id B2A8C61606; Mon, 1 Mar 2021 20:28:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614630499; bh=YoemYxX5fP7QqIIwm3B1ehuIMnFwkmcXLzB8TOLXBmk=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=DonRjxkS9VoNpqJFm7EnJEa9sAYuYYVMZEgMiBMoIIjZTFDsU3D4VsZII40Yf6CIm EVK0whgQft2ymSyACZkiPrdzL4xnxO39gW4nl3pOb4x3oU9+rAWRSn0neupGD3txSx NjM+2Qs/mZC0grudpOTScJ6GVUtbz4GtPCEMzWHT2J6Hpl5asr+aECEm71RrtvswCA mLn9KVL1VZmdWed1dYhD2ImQ1sPwmO8QhbR3rjIF1ZmLpb/JoKRPszD7LzMGVyCK4/ DOA58GXZDizgAU8W2Q8PGaNmasQB1WqnhCvTGkpxZ2dfdQreUfY4eohJL70VaQtY8R BhpgTIEAqN8qw== Date: Mon, 1 Mar 2021 14:28:17 -0600 From: Bjorn Helgaas To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Bjorn Helgaas , Lorenzo Pieralisi , Marek =?iso-8859-1?Q?Beh=FAn?= , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Alex Williamson Subject: Re: RFC: sysfs node for Secondary PCI bus reset (PCIe Hot Reset) Message-ID: <20210301202817.GA201451@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210301171221.3d42a55i7h5ubqsb@pali> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [+cc Alex, reset expert] On Mon, Mar 01, 2021 at 06:12:21PM +0100, Pali Rohár wrote: > Hello! > > PCIe card can be reset via in-band Hot Reset signal which can be > triggered by PCIe bridge via Secondary Bus Reset bit in PCI config > space. > > Kernel already exports sysfs node "reset" for triggering Functional > Reset of particular function of PCI device. But in some cases Functional > Reset is not enough and Hot Reset is required. > > Following RFC patch exports sysfs node "reset_bus" for PCI bridges which > triggers Secondary Bus Reset and therefore for PCIe bridges it resets > connected PCIe card. > > What do you think about it? > > Currently there is userspace script which can trigger PCIe Hot Reset by > modifying PCI config space from userspace: > > https://alexforencich.com/wiki/en/pcie/hot-reset-linux > > But because kernel already provides way how to trigger Functional Reset > it could provide also way how to trigger PCIe Hot Reset. > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > index 50fcb62d59b5..f5e11c589498 100644 > --- a/drivers/pci/pci-sysfs.c > +++ b/drivers/pci/pci-sysfs.c > @@ -1321,6 +1321,30 @@ static ssize_t reset_store(struct device *dev, struct device_attribute *attr, > > static DEVICE_ATTR(reset, 0200, NULL, reset_store); > > +static ssize_t reset_bus_store(struct device *dev, struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + struct pci_dev *pdev = to_pci_dev(dev); > + unsigned long val; > + ssize_t result = kstrtoul(buf, 0, &val); > + > + if (result < 0) > + return result; > + > + if (val != 1) > + return -EINVAL; > + > + pm_runtime_get_sync(dev); > + result = pci_bridge_secondary_bus_reset(pdev); > + pm_runtime_put(dev); > + if (result < 0) > + return result; > + > + return count; > +} > + > +static DEVICE_ATTR(reset_bus, 0200, NULL, reset_bus_store); > + > static int pci_create_capabilities_sysfs(struct pci_dev *dev) > { > int retval; > @@ -1332,8 +1356,15 @@ static int pci_create_capabilities_sysfs(struct pci_dev *dev) > if (retval) > goto error; > } > + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) { > + retval = device_create_file(&dev->dev, &dev_attr_reset_bus); > + if (retval) > + goto error_reset_bus; > + } > return 0; > > +error_reset_bus: > + device_remove_file(&dev->dev, &dev_attr_reset); > error: > pcie_vpd_remove_sysfs_dev_files(dev); > return retval; > @@ -1414,6 +1445,8 @@ static void pci_remove_capabilities_sysfs(struct pci_dev *dev) > device_remove_file(&dev->dev, &dev_attr_reset); > dev->reset_fn = 0; > } > + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) > + device_remove_file(&dev->dev, &dev_attr_reset_bus); > } > > /**