From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com ([134.134.136.20]:10537 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725783AbeHPW2r (ORCPT ); Thu, 16 Aug 2018 18:28:47 -0400 Date: Thu, 16 Aug 2018 22:28:05 +0300 From: Mika Westerberg To: Alex Williamson Cc: Bjorn Helgaas , linux-pci@vger.kernel.org Subject: Re: [PATCH] PCI: Add ACS quirk for Intel 300 series chipset Message-ID: <20180816192805.GN2343@lahna.fi.intel.com> References: <20180427104423.2203-1-mika.westerberg@linux.intel.com> <20180815152139.4e469fd4@t450s.home> <20180815164308.6ad5dd39@t450s.home> <20180816061015.GD2343@lahna.fi.intel.com> <20180816091303.69ce8e45@t450s.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180816091303.69ce8e45@t450s.home> Sender: linux-pci-owner@vger.kernel.org List-ID: On Thu, Aug 16, 2018 at 09:13:03AM -0600, Alex Williamson wrote: > static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev) > { > int pos; > + u16 std_ctrl; > u32 cap, ctrl; > > if (!pci_quirk_intel_spt_pch_acs_match(dev)) > @@ -4621,6 +4628,18 @@ static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev) > if (!pos) > return -ENOTTY; > > + /* If the std control word has bits set or is writable, do not quirk */ > + pci_read_config_word(dev, pos + PCI_ACS_CTRL, &std_ctrl); > + if (std_ctrl) > + return -ENOTTY; > + > + pci_write_config_word(dev, pos + PCI_ACS_CTRL, 0xff); I don't know ACS well but could the above have some unwanted side-effects, even if we write back zeroes below? > + pci_read_config_word(dev, pos + PCI_ACS_CTRL, &std_ctrl); > + if (std_ctrl) { > + pci_write_config_word(dev, pos + PCI_ACS_CTRL, 0); > + return -ENOTTY; > + } > + > pci_read_config_dword(dev, pos + PCI_ACS_CAP, &cap); > pci_read_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, &ctrl); >