From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753885AbdLMVY2 (ORCPT ); Wed, 13 Dec 2017 16:24:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:51516 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753360AbdLMVY0 (ORCPT ); Wed, 13 Dec 2017 16:24:26 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA9CA218AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=helgaas@kernel.org Date: Wed, 13 Dec 2017 15:24:21 -0600 From: Bjorn Helgaas To: Govinda Tatti Cc: jgross@suse.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, JBeulich@suse.com, bhelgaas@google.com, xen-devel@lists.xenproject.org, boris.ostrovsky@Oracle.COM, roger.pau@citrix.com, Christoph Hellwig Subject: Re: [Xen-devel] [PATCH V3 1/2] Drivers/PCI: Export pcie_has_flr() interface Message-ID: <20171213212420.GH30595@bhelgaas-glaptop.roam.corp.google.com> References: <20171207222145.9769-1-Govinda.Tatti@Oracle.COM> <20171207222145.9769-2-Govinda.Tatti@Oracle.COM> <20171208202424.GC12367@bhelgaas-glaptop.roam.corp.google.com> <426eeeab-0dcd-8de3-9c5f-a166acf2c130@Oracle.COM> <20171212005919.GB30595@bhelgaas-glaptop.roam.corp.google.com> <49956aaf-5fd5-939d-5fc7-231ffdb98b70@Oracle.COM> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <49956aaf-5fd5-939d-5fc7-231ffdb98b70@Oracle.COM> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [+cc Christoph] On Wed, Dec 13, 2017 at 02:46:57PM -0600, Govinda Tatti wrote: > > >>>>-static bool pcie_has_flr(struct pci_dev *dev) > >>>>+bool pcie_has_flr(struct pci_dev *dev) > >>>> { > >>>> u32 cap; > >>>>@@ -3882,6 +3882,7 @@ static bool pcie_has_flr(struct pci_dev *dev) > >>>> pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap); > >>>> return cap & PCI_EXP_DEVCAP_FLR; > >>>> } > >>>>+EXPORT_SYMBOL_GPL(pcie_has_flr); > >>>I'd rather change pcie_flr() so you could *always* call it, and it > >>>would return 0, -ENOTTY, or whatever, based on whether FLR is > >>>supported. Is that feasible? > >>Sure, I will add pcie_has_flr() logic inside pcie_flr() and return > >>appropriate > >>values as suggested by you. Do we still want to retain pcie_has_flr() and > >>its usage inside pci.c?.Otherwise, I will remove it and do required cleanup. > >If you can restructure the code and remove pcie_has_flr() while > >retaining the existing behavior of its callers, that would be great. > I checked the current usage of pcie_has_flr() and pcie_flr(). I have > a couple > of questions or need some clarification. > > 1. pcie_has_flr() usage inside pci_probe_reset_function(). > >    This function is only calling pcie_has_flr() but not pcie_flr(). >    Rest of the code is trying to do specific type of reset except > pcie_flr(). > >         rc = pci_dev_specific_reset(dev, 1); >         if (rc != -ENOTTY) >                 return rc; >         if (pcie_has_flr(dev)) >                 return 0; >         rc = pci_af_flr(dev, 1); >         if (rc != -ENOTTY) >                 return rc; > >    In other-words, I can remove usage of pcie_has_flr() in all other places >    in pci.c except in above function. I think we should keep the EXPORT_SYMBOL_GPL() part of a60a2b73ba69 ("PCI: Export pcie_flr()"), but revert the restructuring part. Prior to a60a2b73ba69, we had int pcie_flr(struct pci_dev *dev, int probe); like all the other reset methods. AFAICT, the addition of pcie_has_flr() was to optimize the path slightly because when drivers call pcie_flr(), they should already know that their hardware supports FLR. But I don't think that optimization is worth the extra code complexity. If we do need to optimize it, we can check this in the core during enumeration and set PCI_DEV_FLAGS_NO_FLR_RESET accordingly. Christoph, chime in if I'm missing something here. > 2. W.r.t pcie_flr(), I am planning to return error code. Currently, > the following >    file/modules are calling this function. My plan is to add a check > for return >    code and print a WANRING message if return code is NON-ZERO. I > hope this is >    sufficient for this patch. > >    drivers/crypto/qat/qat_common/adf_aer.c >    drivers/infiniband/hw/hfi1/chip.c (2 places) >    drivers/net/ethernet/cavium/liquidio/lio_vf_main.c >    drivers/net/ethernet/intel/ixgbe/ixgbe_main.c (2 places) >    drivers/pci/quirks.c (2 places) Checking the return code is probably overkill, since pcie_flr() is void and returns no errors now. The only point of the return value is to tell whether the device supports FLR. If we call it with "probe == 0" there's no useful error to return. Bjorn