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=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 12E8DC41604 for ; Wed, 7 Oct 2020 17:28:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC5BD217BA for ; Wed, 7 Oct 2020 17:28:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728459AbgJGR2y (ORCPT ); Wed, 7 Oct 2020 13:28:54 -0400 Received: from mga12.intel.com ([192.55.52.136]:7786 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728456AbgJGR2x (ORCPT ); Wed, 7 Oct 2020 13:28:53 -0400 IronPort-SDR: K0HIRN/KUmkODLSWpTxVne3OH/b885xBH1cORRpNKIkshKiihbSY9Phg4KQ5dCIh9fItQH9g2K TSZXShCO5ETg== X-IronPort-AV: E=McAfee;i="6000,8403,9767"; a="144411819" X-IronPort-AV: E=Sophos;i="5.77,347,1596524400"; d="scan'208";a="144411819" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Oct 2020 10:28:51 -0700 IronPort-SDR: 0e/WL67OF1SS3EUzmvW2mir+firZR9ovDYD8JbaZS63+sZHvwi1Am/7iTu3v5+y1B01G4PiStF BEp+pd2EnllQ== X-IronPort-AV: E=Sophos;i="5.77,347,1596524400"; d="scan'208";a="311835366" Received: from jdelcan-mobl.amr.corp.intel.com (HELO [10.254.64.135]) ([10.254.64.135]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Oct 2020 10:28:51 -0700 Subject: Re: [PATCH v8 2/6] PCI/DPC: define a function to check and wait till port finish DPC handling To: Ethan Zhao , bhelgaas@google.com, oohall@gmail.com, ruscur@russell.cc, lukas@wunner.de, andriy.shevchenko@linux.intel.com, stuart.w.hayes@gmail.com, mr.nuke.me@gmail.com, mika.westerberg@linux.intel.com Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, ashok.raj@linux.intel.com, xerces.zhao@gmail.com References: <20201007113158.48933-1-haifeng.zhao@intel.com> <20201007113158.48933-3-haifeng.zhao@intel.com> From: "Kuppuswamy, Sathyanarayanan" Message-ID: <4bedeb35-942e-5ad3-9721-62495af1f09a@intel.com> Date: Wed, 7 Oct 2020 10:28:50 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201007113158.48933-3-haifeng.zhao@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 10/7/20 4:31 AM, Ethan Zhao wrote: > Once root port DPC capability is enabled and triggered, at the beginning > of DPC is triggered, the DPC status bits are set by hardware and then > sends DPC/DLLSC/PDC interrupts to OS DPC and pciehp drivers, it will > take the port and software DPC interrupt handler 10ms to 50ms (test data > on ICS(Ice Lake SP platform, see > https://en.wikichip.org/wiki/intel/microarchitectures/ice_lake_(server) > & stable 5.9-rc6) to complete the DPC containment procedure This data is based on one particular architecture. So using this to create a timed loop in pci_wait_port_outdpc() looks incorrect. I still recommend looking for some locking model to fix this issue (may be atomic state flag or lock). > till the DPC status is cleared at the end of the DPC interrupt handler. > > We use this function to check if the root port is in DPC handling status > and wait till the hardware and software completed the procedure. > > Signed-off-by: Ethan Zhao > Tested-by: Wen Jin > Tested-by: Shanshan Zhang > --- > changes: > v2：align ICS code name to public doc. > v3: no change. > v4: response to Christoph's (Christoph Hellwig ) > tip, move pci_wait_port_outdpc() to DPC driver and its declaration > to pci.h. > v5: fix building issue reported by lkp@intel.com with some config. > v6: move from [1/5] to [2/5]. > v7: no change. > v8: no change. > > drivers/pci/pci.h | 2 ++ > drivers/pci/pcie/dpc.c | 27 +++++++++++++++++++++++++++ > 2 files changed, 29 insertions(+) > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index fa12f7cbc1a0..455b32187abd 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -455,10 +455,12 @@ void pci_restore_dpc_state(struct pci_dev *dev); > void pci_dpc_init(struct pci_dev *pdev); > void dpc_process_error(struct pci_dev *pdev); > pci_ers_result_t dpc_reset_link(struct pci_dev *pdev); > +bool pci_wait_port_outdpc(struct pci_dev *pdev); > #else > static inline void pci_save_dpc_state(struct pci_dev *dev) {} > static inline void pci_restore_dpc_state(struct pci_dev *dev) {} > static inline void pci_dpc_init(struct pci_dev *pdev) {} > +static inline bool pci_wait_port_outdpc(struct pci_dev *pdev) { return false; } > #endif > > #ifdef CONFIG_PCI_ATS > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c > index daa9a4153776..2e0e091ce923 100644 > --- a/drivers/pci/pcie/dpc.c > +++ b/drivers/pci/pcie/dpc.c > @@ -71,6 +71,33 @@ void pci_restore_dpc_state(struct pci_dev *dev) > pci_write_config_word(dev, dev->dpc_cap + PCI_EXP_DPC_CTL, *cap); > } > > +bool pci_wait_port_outdpc(struct pci_dev *pdev) > +{ > + u16 cap = pdev->dpc_cap, status; > + u16 loop = 0; > + > + if (!cap) { > + pci_WARN_ONCE(pdev, !cap, "No DPC capability initiated\n"); > + return false; > + } > + pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status); > + pci_dbg(pdev, "DPC status %x, cap %x\n", status, cap); > + > + while (status & PCI_EXP_DPC_STATUS_TRIGGER && loop < 100) { > + msleep(10); > + loop++; > + pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status); > + } > + > + if (!(status & PCI_EXP_DPC_STATUS_TRIGGER)) { > + pci_dbg(pdev, "Out of DPC %x, cost %d ms\n", status, loop*10); > + return true; > + } > + > + pci_dbg(pdev, "Timeout to wait port out of DPC status\n"); > + return false; > +} > + > static int dpc_wait_rp_inactive(struct pci_dev *pdev) > { > unsigned long timeout = jiffies + HZ; -- Sathyanarayanan Kuppuswamy Linux Kernel Developer