From mboxrd@z Thu Jan 1 00:00:00 1970 From: soren.brinkmann@xilinx.com (=?utf-8?B?U8O2cmVu?= Brinkmann) Date: Wed, 31 Jul 2013 09:26:55 -0700 Subject: Enable arm_global_timer for Zynq brakes boot In-Reply-To: <51F8BC5D.80605@linaro.org> References: <51E7435B.3060605@codeaurora.org> <51ED8DF2.60600@codeaurora.org> <20130722201348.GI453@xsjandreislx> <0735ab8c-0f80-4b64-b2b2-8d4553482c2a@CO9EHSMHS013.ehs.local> <51F66565.7010600@linaro.org> <8d56935e-2a20-46c7-b80a-f779572dd839@CO1EHSMHS014.ehs.local> <51F77D93.4030505@linaro.org> <51F8BC5D.80605@linaro.org> Message-ID: <2ebbb5cd-2755-4082-b434-d276e7225de5@CO1EHSMHS024.ehs.local> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jul 31, 2013 at 09:27:25AM +0200, Daniel Lezcano wrote: > On 07/31/2013 12:34 AM, S?ren Brinkmann wrote: > > On Tue, Jul 30, 2013 at 10:47:15AM +0200, Daniel Lezcano wrote: > >> On 07/30/2013 02:03 AM, S?ren Brinkmann wrote: > >>> Hi Daniel, > >>> > >>> On Mon, Jul 29, 2013 at 02:51:49PM +0200, Daniel Lezcano wrote: > >>> (snip) > >>>> > >>>> the CPUIDLE_FLAG_TIMER_STOP flag tells the cpuidle framework the local > >>>> timer will be stopped when entering to the idle state. In this case, the > >>>> cpuidle framework will call clockevents_notify(ENTER) and switches to a > >>>> broadcast timer and will call clockevents_notify(EXIT) when exiting the > >>>> idle state, switching the local timer back in use. > >>> > >>> I've been thinking about this, trying to understand how this makes my > >>> boot attempts on Zynq hang. IIUC, the wrongly provided TIMER_STOP flag > >>> would make the timer core switch to a broadcast device even though it > >>> wouldn't be necessary. But shouldn't it still work? It sounds like we do > >>> something useless, but nothing wrong in a sense that it should result in > >>> breakage. I guess I'm missing something obvious. This timer system will > >>> always remain a mystery to me. > >>> > >>> Actually this more or less leads to the question: What is this > >>> 'broadcast timer'. I guess that is some clockevent device which is > >>> common to all cores? (that would be the cadence_ttc for Zynq). Is the > >>> hang pointing to some issue with that driver? > >> > >> If you look at the /proc/timer_list, which timer is used for broadcasting ? > > > > So, the correct run results (full output attached). > > > > The vanilla kernel uses the twd timers as local timers and the TTC as > > broadcast device: > > Tick Device: mode: 1 > > Broadcast device > > Clock Event Device: ttc_clockevent > > > > When I remove the offending CPUIDLE flag and add the DT fragment to > > enable the global timer, the twd timers are still used as local timers > > and the broadcast device is the global timer: > > Tick Device: mode: 1 > > Broadcast device > > Clock Event Device: arm_global_timer > > > > Again, since boot hangs in the actually broken case, I don't see way to > > obtain this information for that case. > > Hmm, interesting. Can you give the ouput of /proc/interrupts also with > the global timer ? Sure: # cat /proc/interrupts CPU0 CPU1 27: 14 1 GIC 27 gt 29: 841 843 GIC 29 twd 43: 0 0 GIC 43 ttc_clockevent 82: 563 0 GIC 82 xuartps IPI0: 0 0 CPU wakeup interrupts IPI1: 0 0 Timer broadcast interrupts IPI2: 1266 1330 Rescheduling interrupts IPI3: 0 0 Function call interrupts IPI4: 34 59 Single function call interrupts IPI5: 0 0 CPU stop interrupts Err: 0 S?ren