From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Date: Wed, 19 Mar 2014 15:48:50 +0000 Subject: Re: [PATCH/RFC 0/5] Fix the sh_eth race between open and MDIO bus registration Message-Id: <2759366.H52WfZEWX0@avalon> List-Id: References: <1395185156-6681-1-git-send-email-laurent.pinchart+renesas@ideasonboard.com> In-Reply-To: <1395185156-6681-1-git-send-email-laurent.pinchart+renesas@ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sh@vger.kernel.org Hi Ben, On Wednesday 19 March 2014 16:45:01 Ben Dooks wrote: > On 19/03/14 16:06, Laurent Pinchart wrote: > > On Wednesday 19 March 2014 14:35:59 Geert Uytterhoeven wrote: > >> On Wed, Mar 19, 2014 at 11:07 AM, Laurent Pinchart wrote: > >>> On Wednesday 19 March 2014 10:14:53 Ben Dooks wrote: > >>>> On 19/03/14 08:41, Geert Uytterhoeven wrote: > >>>>> On Wed, Mar 19, 2014 at 12:25 AM, Laurent Pinchart wrote: > >>>>>> Laurent Pinchart (5): > >>>>>> sh_eth: Use the platform device for memory allocation > >>>>>> sh_eth: Use the platform device as the MDIO bus parent > >>>>>> sh_eth: Simplify MDIO bus initialization and release > >>>>>> sh_eth: Register MDIO bus before registering the network device > >>>>>> sh_eth: Remove goto statements that jump straight to a return > >>>>> > >>>>> Thanks, the changes look fine to me, so > >>>> > >>>> I think the only issue I have is the re-parent of the MDIO device. > >>>> > >>>> My view also is that the probe should explicitly get a reference if it > >>>> is going to be created sub-devices. > >>> > >>> I'm not sure to follow you, could you please elaborate on that ? What > >>> should take a reference on what ? > >> > >> I think he means a runtime pm reference, and he is right. > >> > >> I gave your series a try on Koelsch. Now the clock is: > >> 1. enabled in sh_eth_drv_probe(), > >> 2. disabled from the worker thread, > >> 3. enabled and disabled in sh_eth_get_stats(), > >> 4. enabled in sh_eth_open() for nfsroot, > >> 5. disabled in sh_eth_close() on shutdown, > >> 6. enabled and disabled in sh_eth_get_stats(). > >> > >> I wondered whether 2 could happen too soon, so I added msleep(2000) to > >> sh_eth_drv_probe(), just after the call to pm_runtime_resume(). Then it > >> fails to obtain the MAC address: > >> > >> sh-eth ee700000.ethernet: no valid MAC address supplied, using a random > >> one. > >> > >> Due to 4, the network hardware works, and it manages to receive an IP > >> address from my DHCP server. But as the MAC address is wrong, the IP > >> address is also wrong, and it hangs when trying to mount NFS. > >> > >> Applying Ben's "PATCH] sh_eth: ensure pm_runtime cannot suspend the > >> device during init" fixes this. > > > > I've investigated the issue. The pm_runtime_resume() call from the sh_eth > > probe function ends up calling rpm_resume() synchronously. The function > > resumes the device, and right before returning calls rpm_idle(dev, > > RPM_ASYNC). This queues a RPM_REQ_IDLE request, resulting in the device > > being suspended the next time the work queue is run. > > > > pm_runtime_resume() seem to be unsafe at probe time if the PM workqueue > > can run before the probe function is done with the device, which means > > pretty much everywhere as probe() usually calls functions that can sleep. > > > > I thus agree that a pm_runtime_get_sync() call is needed. The > > pm_runtime_put_sync() call at the end of the probe function could be > > replaced by a pm_runtime_put() call though. The PM runtime documentation > > should also be updated. > > Thanks, that validates what I saw but did not get time to fully > trace. > > I agree that pm_runtime_put() is probably a better option as we do > not need to ensure that the device is shut down immediately. I will > re-do the patch and submit it tonight. Thank you. Could you please also submit a patch that fixes the runtime PM documentation ? It doesn't have to be long, but driver writers should be warned of the potential pm_runtime_resume() issues. This should also help getting a reply from the runtime PM developers. -- Regards, Laurent Pinchart