From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartlomiej Zolnierkiewicz Subject: Re: [PATCH 1/2] hpt366: fix PCI clock detection for HPT374 Date: Sat, 11 Aug 2007 19:07:29 +0200 Message-ID: <200708111907.29501.bzolnier@gmail.com> References: <200708060006.35511.sshtylyov@ru.mvista.com> <200708111841.34648.bzolnier@gmail.com> <46BDE9D4.1020702@ru.mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from fk-out-0910.google.com ([209.85.128.186]:28090 "EHLO fk-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751747AbXHKRK7 (ORCPT ); Sat, 11 Aug 2007 13:10:59 -0400 Received: by fk-out-0910.google.com with SMTP id z23so989451fkz for ; Sat, 11 Aug 2007 10:10:57 -0700 (PDT) In-Reply-To: <46BDE9D4.1020702@ru.mvista.com> Content-Disposition: inline Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Sergei Shtylyov Cc: Alan Cox , rah@bash.sh, linux-ide@vger.kernel.org On Saturday 11 August 2007, Sergei Shtylyov wrote: > Bartlomiej Zolnierkiewicz wrote: > > >>>>>>>>+ if (chip_type == HPT374 && (PCI_FUNC(dev->devfn) & 1)) { > >>>>>>>>+ struct pci_dev *dev1 = pci_get_slot(dev->bus, > >>>>>>>>+ dev->devfn - 1); > > >>>>>>>Can be NULL > > >>>>>> Not really. This may not be called if it's NULL -- see hpt374_init_setup(). > >>>>>>Maybe worth a comment though... > > >>>>>>>>+ unsigned long io_base = pci_resource_start(dev1, 4); > > >>>>>>>Kaboom > > >>>>>> That was a dud bomb. ;-) > > >>>>>What stops a hot unplug of a 374 from causing that to occur. I don't see > > >>>> Pinned as in pci_get_device()? If so, see setup-ide.c:ide_scan_pcibus(). > >>>>The IDE core does that for me. > > >>>ide_scan_pcibus() is used iff IDE is built-in. > > >>>Moreover pci_get_device() holds reference _only_ to the current PCI device > >>>(the reference count to @from PCI device is _always_ decremented). > > >> Indeed... doesn't it look like a buglet in the IDE core? > > > It is OK, when ide_scan_pcibus() is not used > > But whan it is used? Then it keeps the reference to PCI device itself by using pci_get_device()... > > probing is done by PCI layer > > and it keeps the reference to the PCI device in pci_device_probe(). > > >>>>>where you have the other pci_dev pinned on a hotplug on a box set to scan > >>>>>the devices in reverse order > > >>>> Function 1 will always be skipped, regardless of the scan order. > > >>>Yes, but init_chipset_hpt366() will still try to access Function 1 > > >> No! Re-read the code please: init_chipset_hpt366() won't be called for > >>function 1 if that one is not detected, and only in this case it does function > >>0 access to read the saved f_CNT value. > > > Argh, thinko on my side. > > Alas, it's your thinko, *again*. ;-) > > > Unfortunately patch needs fixing anyway since the new comment is incorrect > > because the reference is kept by hpt366 driver itself - pci_get_slot() in > > init_setup_hpt374() - not the IDE core... > > Actually, init_setup_hpt374() grabs function 1 to register pair of devices > (in hopes that the callers have already "pinned" function 0), and > init_chipset_hpt366() "pins" function 0 to read the saved f_CNT. Yep, this would make a nice code comment instead the current one. :) Bart