From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com ([134.134.136.20]:41048 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751058AbdHUGd1 (ORCPT ); Mon, 21 Aug 2017 02:33:27 -0400 Subject: Re: [PATCH] usb: optimize acpi companion search for usb port devices To: Greg Kroah-Hartman References: <1503054177-2490-1-git-send-email-mathias.nyman@linux.intel.com> <20170818161700.GB9858@kroah.com> Cc: stable@vger.kernel.org From: Mathias Nyman Message-ID: <599A7F85.3000006@linux.intel.com> Date: Mon, 21 Aug 2017 09:36:53 +0300 MIME-Version: 1.0 In-Reply-To: <20170818161700.GB9858@kroah.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: On 18.08.2017 19:17, Greg Kroah-Hartman wrote: > On Fri, Aug 18, 2017 at 02:02:57PM +0300, Mathias Nyman wrote: >> commit ed18c5fa945768a9bec994e786edbbbc7695acf6 upstream >> >> This optimization significantly reduces xhci driver load time. >> >> In ACPI tables the acpi companion port devices are children of >> the hub device. The port devices are identified by their port number >> returned by the ACPI _ADR method. >> _ADR 0 is reserved for the root hub device. >> >> The current implementation to find a acpi companion port device >> loops through all acpi port devices under that parent hub, evaluating >> their _ADR method each time a new port device is added. >> >> for a xHC controller with 25 ports under its roothub it >> will end up invoking ACPI bytecode 625 times before all ports >> are ready, making it really slow. >> >> The _ADR values are already read and cached earler. So instead of >> running the bytecode again we can check the cached _ADR value first, >> and then fall back to the old way. >> >> As one of the more significant changes, the xhci load time on >> Intel kabylake reduced by 70%, (28ms) from >> initcall xhci_pci_init+0x0/0x49 returned 0 after 39537 usecs >> to >> initcall xhci_pci_init+0x0/0x49 returned 0 after 11270 usecs >> >> Signed-off-by: Mathias Nyman >> Signed-off-by: Greg Kroah-Hartman >> --- >> drivers/usb/core/usb-acpi.c | 26 +++++++++++++++++++++++--- >> 1 file changed, 23 insertions(+), 3 deletions(-) > > What stable kernel tree(s) is this for? > Oh, right, should have mentioned that as well. 4.4 and later Thanks Mathias