Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753090AbcLIWo2 (ORCPT ); Fri, 9 Dec 2016 17:44:28 -0500 Received: from mga07.intel.com ([134.134.136.100]:20781 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752437AbcLIWo0 (ORCPT ); Fri, 9 Dec 2016 17:44:26 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,325,1477983600"; d="scan'208";a="1097117199" From: Vaibhav Shankar To: bhelgaas@google.com, vaibhav.shankar@intel.com Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, venkateswarlu.v.vinjamuri@intel.com Subject: [PATCH] PCI: pciehp: Optimize PCIe root resume time Date: Fri, 9 Dec 2016 14:43:26 -0800 Message-Id: <1481323406-12865-1-git-send-email-vaibhav.shankar@intel.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1942 Lines: 47 On Apollolake platforms, PCIe rootport takes a long time to resume from S3. With 100ms delay before read pci conf, rootport takes ~200ms during resume. commit 2f5d8e4ff947 ("PCI: pciehp: replace unconditional sleep with config space access check") is the one that added the 100ms delay before reading pci conf. This patch removes the 100ms delay.By removing the delay, the PCIe root port takes ~16ms during resume. As per PCIe spec, we only require 1000ms delay. This delay is provide by pci_bus_check_dev() function. With 100ms delay: [ 155.102713] calling 0000:00:14.0+ @ 70, parent: pci0000:00, cb: pci_pm_resume_noirq [ 155.119337] call 0000:00:14.0+ returned 0 after 16231 usecs [ 155.119467] calling 0000:01:00.0+ @ 5845, parent: 0000:00:14.0, cb: pci_pm_resume_noirq [ 155.321670] call 0000:00:14.0+ returned 0 after 185327 usecs [ 155.321743] calling 0000:01:00.0+ @ 5849, parent: 0000:00:14.0, cb: pci_pm_resume After removing 100ms delay: [ 36.624709] calling 0000:00:14.0+ @ 4434, parent: pci0000:00, cb: pci_pm_resume_noirq [ 36.641367] call 0000:00:14.0+ returned 0 after 16263 usecs [ 36.652458] calling 0000:00:14.0+ @ 4443, parent: pci0000:00, cb: pci_pm_resume [ 36.652673] call 0000:00:14.0+ returned 0 after 208 usecs [ 36.652863] calling 0000:01:00.0+ @ 4442, parent: 0000:00:14.0, cb: pci_pm_resume Signed-off-by: Vaibhav Shankar --- drivers/pci/hotplug/pciehp_hpc.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index 5c24e93..08357e7 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -311,8 +311,6 @@ int pciehp_check_link_status(struct controller *ctrl) else msleep(1000); - /* wait 100ms before read pci conf, and try in 1s */ - msleep(100); found = pci_bus_check_dev(ctrl->pcie->port->subordinate, PCI_DEVFN(0, 0)); -- 1.7.9.5