Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750848AbWLLBi3 (ORCPT ); Mon, 11 Dec 2006 20:38:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750843AbWLLBi3 (ORCPT ); Mon, 11 Dec 2006 20:38:29 -0500 Received: from sj-iport-4.cisco.com ([171.68.10.86]:7384 "EHLO sj-iport-4.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750825AbWLLBi2 (ORCPT ); Mon, 11 Dec 2006 20:38:28 -0500 To: Benjamin Herrenschmidt Cc: Stephen Hemminger , Greg Kroah-Hartman , linux-pci@atrey.karlin.mff.cuni.cz, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/6] MTHCA driver (infiniband) use new pci interfaces X-Message-Flag: Warning: May contain useful information References: <20061208182241.786324000@osdl.org> <20061208182500.611327000@osdl.org> <1165809339.7260.19.camel@localhost.localdomain> From: Roland Dreier Date: Mon, 11 Dec 2006 17:38:24 -0800 In-Reply-To: <1165809339.7260.19.camel@localhost.localdomain> (Benjamin Herrenschmidt's message of "Mon, 11 Dec 2006 14:55:39 +1100") Message-ID: User-Agent: Gnus/5.1007 (Gnus v5.10.7) XEmacs/21.4.19 (linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-OriginalArrivalTime: 12 Dec 2006 01:38:24.0924 (UTC) FILETIME=[3708E5C0:01C71D8E] Authentication-Results: sj-dkim-7; header.From=rdreier@cisco.com; dkim=pass ( sig from cisco.com/sjdkim7002 verified; ); Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1193 Lines: 28 > I'm worried by this... At no point do you check the host bridge > capabilities, and thus will happily set the max read req size to some > value larger than the max the host bridge can cope... Well, it's disabled by default... the option is there as a quick way to fix "why is my bandwidth so low" when a broken BIOS sets these to minimum values. Maybe we should just strip out that code and point people who want to tweak this at setpci instead. > So for PCI-X, if we want tat, we need a pcibios hook for the platform > to validate the size requested. For PCI-E, we can use standard code to > look for the root complex (and bridges on the path to it) and get the > proper max value. Actually even PCIe might not be that easy. For example with current kernels on PowerPC 440SPe (SoC with PCIe), I just get: # lspci 00:01.0 InfiniBand: Mellanox Technology: Unknown device 6274 (rev a0) ie no host bridge / root complex. - R. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/