From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Helgaas Subject: mlx4 fails ("go bit not cleared") without MSI Date: Wed, 13 Jan 2016 16:08:43 -0600 Message-ID: <20160113220843.GA21544@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Eugenia Emantayev Return-path: Received: from mail.kernel.org ([198.145.29.136]:40075 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755184AbcAMWIp (ORCPT ); Wed, 13 Jan 2016 17:08:45 -0500 Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hi Eugenia, Due to my own stupidity, I tried to use mlx4 without turning on CONFIG_PCI_MSI=y. The driver failed miserably: pci 0000:01:00.0: [15b3:1007] type 00 class 0x020000 mlx4_core: Mellanox ConnectX core driver v2.2-1 (Feb, 2014) mlx4_core: Initializing 0000:01:00.0 mlx4_core 0000:01:00.0: PCIe link speed is 8.0GT/s, device supports 8.0GT/s mlx4_core 0000:01:00.0: PCIe link width is x8, device supports x8 mlx4_core 0000:01:00.0: command 0x23 timed out (go bit not cleared) mlx4_core 0000:01:00.0: device is going to be reset mlx4_core 0000:01:00.0: device was reset successfully mlx4_core 0000:01:00.0: Failed to initialize queue pair table, aborting mlx4_core: probe of 0000:01:00.0 failed with error -5 The lack of MSI was my own fault, but it took me a long time to figure it out. The fact that mlx4 has a "msi_x" module parameter makes me think that mlx4 is *supposed* to work without MSI. Would you consider either fixing the non-MSI fallback path, or printing a warning when the driver can't set up MSIs? This is easy to reproduce; just turn off CONFIG_PCI_MSI or boot with "pci=nomsi". Bjorn