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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 B9C1DCA9EAF for ; Mon, 21 Oct 2019 13:41:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 963902166E for ; Mon, 21 Oct 2019 13:41:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729672AbfJUNlU (ORCPT ); Mon, 21 Oct 2019 09:41:20 -0400 Received: from mga12.intel.com ([192.55.52.136]:25753 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729656AbfJUNlR (ORCPT ); Mon, 21 Oct 2019 09:41:17 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Oct 2019 06:41:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,323,1566889200"; d="scan'208";a="209446042" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.157]) by fmsmga001.fm.intel.com with SMTP; 21 Oct 2019 06:41:12 -0700 Received: by lahna (sSMTP sendmail emulation); Mon, 21 Oct 2019 16:41:11 +0300 Date: Mon, 21 Oct 2019 16:41:11 +0300 From: Mika Westerberg To: Stuart Hayes Cc: Bjorn Helgaas , Austin Bolen , keith.busch@intel.com, Alexandru Gagniuc , "Rafael J . Wysocki" , Andy Shevchenko , "Gustavo A . R . Silva" , Sinan Kaya , Oza Pawandeep , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, lukas@wunner.de Subject: Re: [PATCH v3 2/3] PCI: pciehp: Wait for PDS if in-band presence is disabled Message-ID: <20191021134111.GK2819@lahna.fi.intel.com> References: <20191017193256.3636-1-stuart.w.hayes@gmail.com> <20191017193256.3636-3-stuart.w.hayes@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191017193256.3636-3-stuart.w.hayes@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 17, 2019 at 03:32:55PM -0400, Stuart Hayes wrote: > From: Alexandru Gagniuc > > When inband presence is disabled, PDS may come up at any time, or not > at all. PDS being low may indicate that the card is still mating, and > we could expect contact bounce to bring down the link as well. > > It is reasonable to assume that most cards will mate in a hotplug slot > in about a second. Thus, when we know PDS only reflects out-of-band > presence, it's worthwhile to wait the extra second or so to make sure > the card is properly mated before loading the driver, and to prevent > the hotplug code from disabling a device if the presence detect change > goes active after the device is enabled. > > Signed-off-by: Alexandru Gagniuc > Signed-off-by: Stuart Hayes Reviewed-by: Mika Westerberg One nit below. > --- > v2: > replace while(true) loop with do...while > v3 > remove unused variable declaration (pds) > modify text of warning message > > drivers/pci/hotplug/pciehp_hpc.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c > index dc109d521f30..02eb811a014f 100644 > --- a/drivers/pci/hotplug/pciehp_hpc.c > +++ b/drivers/pci/hotplug/pciehp_hpc.c > @@ -242,6 +242,22 @@ static bool pci_bus_check_dev(struct pci_bus *bus, int devfn) > return found; > } > > +static void pcie_wait_for_presence(struct pci_dev *pdev) > +{ > + int timeout = 1250; > + u16 slot_status; > + > + do { > + pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status); > + if (!!(slot_status & PCI_EXP_SLTSTA_PDS)) It is more readable if you write it like: if (slot_status & PCI_EXP_SLTSTA_PDS) > + return; > + msleep(10); > + timeout -= 10; > + } while (timeout > 0); > + > + pci_info(pdev, "Timeout waiting for Presence Detect state to be set\n"); > +} > + > int pciehp_check_link_status(struct controller *ctrl) > { > struct pci_dev *pdev = ctrl_dev(ctrl); > @@ -251,6 +267,9 @@ int pciehp_check_link_status(struct controller *ctrl) > if (!pcie_wait_for_link(pdev, true)) > return -1; > > + if (ctrl->inband_presence_disabled) > + pcie_wait_for_presence(pdev); > + > found = pci_bus_check_dev(ctrl->pcie->port->subordinate, > PCI_DEVFN(0, 0)); > > -- > 2.18.1