From mboxrd@z Thu Jan 1 00:00:00 1970 From: santosh shilimkar Subject: Re: [PATCH v4 13/21] ARM: omap: convert wakeupgen to stacked domains Date: Wed, 21 Jan 2015 13:28:11 -0800 Message-ID: <54C019EB.5030007@oracle.com> References: <1421660655-21394-1-git-send-email-marc.zyngier@arm.com> <1421660655-21394-14-git-send-email-marc.zyngier@arm.com> <20150121163031.GR7718@atomide.com> <54BFE05E.9080403@arm.com> <20150121183615.GS7718@atomide.com> <54C00832.1070807@oracle.com> <20150121204347.GT7718@atomide.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150121204347.GT7718@atomide.com> Sender: linux-samsung-soc-owner@vger.kernel.org To: Tony Lindgren Cc: Marc Zyngier , Stephen Warren , Thierry Reding , Alexandre Courbot , Benoit Cousson , Nishanth Menon , Santosh Shilimkar , Shawn Guo , Sascha Hauer , Kukjin Kim , Pankaj Dubey , Simon Horman , Magnus Damm , Linus Walleij , Michal Simek , Rob Herring , Mark Rutland , Jason Cooper , Thomas Gleixner , Stefan Agner , "linux-arm-kernel@lists.infradead.org" , "linux-samsung-soc@vger.kernel.org" List-Id: linux-omap@vger.kernel.org On 1/21/2015 12:43 PM, Tony Lindgren wrote: > * santosh shilimkar [150121 12:16]: >> On 1/21/2015 10:36 AM, Tony Lindgren wrote: >>> * Marc Zyngier [150121 09:25]: >>>> On 21/01/15 16:30, Tony Lindgren wrote: >>>> >>>>> I gave this a quick boot test on am437x-gp-evm and the >>>>> interrupts look OK with the fix also applied: >>>>> >>>>> # cat /proc/interrupts >>>>> CPU0 >>>>> 16: 657 WUGEN 68 gp_timer >>>>> 18: 0 WUGEN 9 l3-dbg-irq >>>>> 19: 0 WUGEN 10 l3-app-irq >>>>> 20: 5 WUGEN 12 edma >>>>> 22: 0 WUGEN 14 edma_error >>>>> 23: 96 WUGEN 72 OMAP UART0 >>>>> 33: 0 44e07000.gpio 6 mmc0 >>>>> 158: 52 WUGEN 70 44e0b000.i2c >>>>> 159: 0 WUGEN 71 4802a000.i2c >>>>> 160: 35 WUGEN 64 mmc0 >>>>> 161: 0 WUGEN 40 4a100000.ethernet >>>>> 162: 7739 WUGEN 41 4a100000.ethernet >>>>> 163: 7608 WUGEN 42 4a100000.ethernet >>>>> 164: 0 WUGEN 43 4a100000.ethernet >>>>> 170: 0 WUGEN 100 gpmc >>>>> 180: 0 WUGEN 7 tps65218 >>>>> IPI0: 0 CPU wakeup interrupts >>>>> IPI1: 0 Timer broadcast interrupts >>>>> IPI2: 0 Rescheduling interrupts >>>>> IPI3: 0 Function call interrupts >>>>> IPI4: 0 Single function call interrupts >>>>> IPI5: 0 CPU stop interrupts >>>>> IPI6: 0 IRQ work interrupts >>>>> IPI7: 0 completion interrupts >>>>> Err: 0 >>>> >>>> Interesting. No TWD timer on this one? >>> >>> Good question, adding Felipe to cc. It eems to be there in >>> the TRM in "Table 2-3. L4_PER Peripheral Memory Map" as >>> MPU_PRV_TIMERS. Also seems to actually work with the >>> attached patch: >>> >> TWD is useless on this machine since single core and TWD >> as know die in low power states. All the broadcast stuff >> is for SMP machines. > > Hmm it seems we should still use TWD during runtime and > swich over to the gptimer for idle states for wake-up > events. > Well timer wheel code don't support it so if you are serious, some one needs to do that. For me, it is not worth at all. You will have more to loose than gain with these time switching schemes since you have to keep 2 times alive, do switching, loose the idle time. All of that is to save few CPU cycles since TWD is closer compared to other SOC timer. Anyways I will let you fight it out but IIRC, I had a discussion a while back with tglx in one of the conference and the conclusion was it not worth doing. Rather TWD hardware on SOC should be made wakeup capable and then everything is good. Till you have support, using TWD on AM43XX will break CPUIDLE. Not sure if it is supported or some one cares about it. Just keep that aspect in mind. Regards, Santosh