From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:14083 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752447AbaG2Qno (ORCPT ); Tue, 29 Jul 2014 12:43:44 -0400 Message-ID: <1406652178.1011.191.camel@ul30vt.home> Subject: Re: [PATCH] PCI: update device mps when doing pci hotplug From: Alex Williamson To: Keith Busch Cc: Yijing Wang , Bjorn Helgaas , linux-pci@vger.kernel.org, Jordan_Hargrave@Dell.com, jon.mason@intel.com, Jon Mason Date: Tue, 29 Jul 2014 10:42:58 -0600 In-Reply-To: References: <1406621877-12022-1-git-send-email-wangyijing@huawei.com> <1406650687.1011.180.camel@ul30vt.home> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org List-ID: On Tue, 2014-07-29 at 10:30 -0600, Keith Busch wrote: > On Tue, 29 Jul 2014, Alex Williamson wrote: > > On Tue, 2014-07-29 at 16:17 +0800, Yijing Wang wrote: > >> Currently we don't update device's mps value when doing > >> pci device hot-add. The hot-added device's mps will be set > >> to default value (128B). But the upstream port device's mps > >> may be larger than 128B which was set by firmware during > >> system bootup. In this case the new added device may not > >> work normally. > > > > Apologies if we rehash some previously discussed topics while I try to > > cover for Bjorn while he's out. By "normally", do you mean "optimally"? > > The device should be functional with a lower mps setting, right? > > You'd think so, but some platforms don't work. A pci-e trace showed > TLPs exceeding MPS when parent device at 256B and the end device left > at 128B. Even if that's a platform bug, I think we still want it to work. But if it's a platform bug for a non-compliant device, should it be handled as a quirk rather than standard configuration? Thanks, Alex