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[24.6.192.50]) by smtp.gmail.com with ESMTPSA id n22-v6sm23804660pfj.68.2018.08.30.21.36.01 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 Aug 2018 21:36:02 -0700 (PDT) Subject: Re: v4.17 regression: PowerMac G3 won't boot, was Re: [PATCH v5 1/3] of: cache phandle nodes to reduce cost of of_find_node_by_phandle() To: Finn Thain Cc: Stan Johnson , Rob Herring , Benjamin Herrenschmidt , Chintan Pandya , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <1520208889-3908-1-git-send-email-frowand.list@gmail.com> <1520208889-3908-2-git-send-email-frowand.list@gmail.com> From: Frank Rowand Message-ID: <0ad5dbfd-08f3-b97d-34b9-70fc9a729921@gmail.com> Date: Thu, 30 Aug 2018 21:36:00 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Finn, On 08/29/18 17:44, Finn Thain wrote: > Hi Frank, > > Linux v4.17 and later will no longer boot on a G3 PowerMac. The boot hangs > very early, before any video driver loads. > > Stan and I were able to bisect the regression between v4.16 and v4.17 and > arrived at commit 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of > of_find_node_by_phandle()"). > > I don't see any obvious bug in 0b3ce78e90fc or b9952b5218ad. But if you > revert these from v4.18 (which is also affected) that certainly resolves > the issue. > > I did see this in the kernel messages: > > Duplicate name in PowerPC,750, renamed to "l2-cache#1" > Duplicate name in mac-io, renamed to "ide#1" > Duplicate name in ide#1, renamed to "atapi-disk#1" > Duplicate name in multifunc-device, renamed to "pci1799,1#1" > > No idea whether that's relevant; I haven't done any further investigation. > Complete dmesg output is attached. Please let me know if there's any more > information you need to help find the bug. > > Thanks. I don't have any useful answers yet, but I am following the thread and have also quickly scanned the two commits for any obvious cause. I will look into this some more, but have a few other tasks that I need to complete first. A long shot, but something to consider, is that I failed to cover the cases of dynamic devicetree updates (removing nodes that contain a phandle) in ways other than overlays. Michael Ellerman has reported such a problem for powerpc/mobility with of_detach_node(). A patch to fix that is one of the tasks I need to complete. -Frank