From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-io0-f176.google.com ([209.85.223.176]:43239 "EHLO mail-io0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751330AbdINUgJ (ORCPT ); Thu, 14 Sep 2017 16:36:09 -0400 Received: by mail-io0-f176.google.com with SMTP id k101so3650483iod.0 for ; Thu, 14 Sep 2017 13:36:08 -0700 (PDT) Subject: Re: iwlwifi firmware load broken in current -git To: Srinath Mannam Cc: Bjorn Helgaas , Johannes Berg , Luca Coelho , "Grumbach, Emmanuel" , linuxwifi , "linux-wireless@vger.kernel.org" , "linux-pci@vger.kernel.org" References: <04c9b578-693c-1dc6-9f0f-904580231b21@kernel.dk> <1505232673.5400.243.camel@intel.com> <1505234187.5400.249.camel@coelho.fi> <4bcbcbc1-7c79-09f0-5071-bc2f53bf6574@kernel.dk> <1505246657.1974.11.camel@sipsolutions.net> <8de8d1e2-1673-e1ff-d0ac-6d3bb03e9e99@kernel.dk> <93bfbc9b-8829-66fa-f4d6-6d47124e460c@kernel.dk> From: Jens Axboe Message-ID: (sfid-20170914_223612_268611_1D124169) Date: Thu, 14 Sep 2017 14:36:06 -0600 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 09/14/2017 02:04 PM, Srinath Mannam wrote: > Hi Jens Axboe, > > > On Thu, Sep 14, 2017 at 11:14 PM, Jens Axboe wrote: >> On 09/14/2017 11:35 AM, Jens Axboe wrote: >>> On 09/14/2017 11:28 AM, Srinath Mannam wrote: >>>> Hi Bjorn, >>>> >>>> On Thu, Sep 14, 2017 at 10:52 PM, Jens Axboe wrote: >>>>> >>>>> On 09/14/2017 11:11 AM, Bjorn Helgaas wrote: >>>>>> [+cc linux-pci] >>>>>> >>>>>> On Thu, Sep 14, 2017 at 12:00 PM, Jens Axboe wrote: >>>>>>> On 09/12/2017 02:04 PM, Johannes Berg wrote: >>>>>>>> On Tue, 2017-09-12 at 13:43 -0600, Jens Axboe wrote: >>>>>>>> >>>>>>>>> CC'ing the guilty part and Bjorn. I'm assuming it's the >>>>>>>>> pci_is_enabled() check, since the rest of the patch shouldn't have >>>>>>>>> functional changes. >>>>>>>> >>>>>>>> and pci_enable_bridge() already checks if it's already enabled, but >>>>>>>> still enables mastering in that case if it isn't: >>>>>>>> >>>>>>>> static void pci_enable_bridge(struct pci_dev *dev) >>>>>>>> { >>>>>>>> [...] >>>>>>>> if (pci_is_enabled(dev)) { >>>>>>>> if (!dev->is_busmaster) >>>>>>>> pci_set_master(dev); >>>>>>>> return; >>>>>>>> } >>>>>>>> >>>>>>>> so I guess due to the new check we end up with mastering disabled, and >>>>>>>> thus the firmware can't load since that's a DMA thing? >>>>>>> >>>>>>> Bjorn/Srinath, any input here? This is a regression that prevents wifi >>>>>>> from working on a pretty standard laptop. It'd suck to have this be in >>>>>>> -rc1. Seems like the trivial fix would be: >>>>>>> >>>>>>> >>>>>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >>>>>>> index b0002daa50f3..ffbe11dbdd61 100644 >>>>>>> --- a/drivers/pci/pci.c >>>>>>> +++ b/drivers/pci/pci.c >>>>>>> @@ -1394,7 +1394,7 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) >>>>>>> return 0; /* already enabled */ >>>>>>> >>>>>>> bridge = pci_upstream_bridge(dev); >>>>>>> - if (bridge && !pci_is_enabled(bridge)) >>>>>>> + if (bridge) >>>> With this change and keeping "mutex_lock(&pci_bridge_mutex);" in >>>> pci_enable_bridge functoin will causes a nexted lock. >>> >>> Took a look, and looks like you are right. That code looks like a mess, >>> fwiw. >>> >>> I'd strongly suggest that the bad commit is reverted until a proper >>> solution is found, since the simple one-liner could potentially >>> introduce a deadlock with your patch applied. >> >> BTW, your patch looks pretty bad too, introducing a random mutex >> deep on code that can be recursive. Why isn't this check in >> pci_enable_device_flags() enough to prevent double-enable of >> an upstream bridge? >> >> if (atomic_inc_return(&dev->enable_cnt) > 1) >> return 0; /* already enabled */ >> > This check only to verify device enable not for the bus master check. > But device enable function calls the bridge enable if it has the bridge. > Bridge enable function enables both device and bus master. > > Here the issue might be because, bridge of endpoint has already set > device enable without set bus master in some other context. which is > wrong. > because all bridges should enable with bridge_enable function only. > So we see the problem In this context, because "if (bridge && > !pci_is_enabled(bridge))" check stops bridge enable which intern stops > bus master. > pci_enable_bridge function always makes sure that both device and bus > master are enabled in any case. If pci_enable_bridge function is not > called means, that bridge is already has device enable flag set. which > is not from pci_enable_bridge function. In any case, your patch introduces a regression on systems. Please get it reverted now, and then you can come up with a new approach to fix the double enable of the upstream bridge. -- Jens Axboe