From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com ([192.55.52.93]:33092 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752164AbaG2QbA (ORCPT ); Tue, 29 Jul 2014 12:31:00 -0400 Date: Tue, 29 Jul 2014 10:30:58 -0600 (MDT) From: Keith Busch To: Alex Williamson cc: Yijing Wang , Bjorn Helgaas , linux-pci@vger.kernel.org, Jordan_Hargrave@Dell.com, keith.busch@intel.com, jon.mason@intel.com, Jon Mason Subject: Re: [PATCH] PCI: update device mps when doing pci hotplug In-Reply-To: <1406650687.1011.180.camel@ul30vt.home> Message-ID: References: <1406621877-12022-1-git-send-email-wangyijing@huawei.com> <1406650687.1011.180.camel@ul30vt.home> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-pci-owner@vger.kernel.org List-ID: 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.