Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754821AbbKMTAR (ORCPT ); Fri, 13 Nov 2015 14:00:17 -0500 Received: from devils.ext.ti.com ([198.47.26.153]:39400 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754648AbbKMTAP (ORCPT ); Fri, 13 Nov 2015 14:00:15 -0500 Subject: Re: [PATCH] clocksource: arm_global_timer: fix suspend resume To: Felipe Balbi , , Daniel Lezcano , Thomas Gleixner , Srinivas Kandagatla , Maxime Coquelin References: <1447431951-23713-1-git-send-email-grygorii.strashko@ti.com> <87a8qhq284.fsf@saruman.tx.rr.com> <56461688.1090809@ti.com> <87y4e1ol0g.fsf@saruman.tx.rr.com> <56462742.3020300@ti.com> <87si49ojed.fsf@saruman.tx.rr.com> <56462C0A.6070802@ti.com> <87mvuhoimr.fsf@saruman.tx.rr.com> CC: , , , , Arnd Bergmann , John Stultz , Tony Lindgren From: Grygorii Strashko Message-ID: <56463304.2040009@ti.com> Date: Fri, 13 Nov 2015 20:59:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <87mvuhoimr.fsf@saruman.tx.rr.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5441 Lines: 132 On 11/13/2015 08:32 PM, Felipe Balbi wrote: > > Hi, > > Grygorii Strashko writes: >> On 11/13/2015 08:15 PM, Felipe Balbi wrote: >>> >>> Hi, >>> >>> Grygorii Strashko writes: >>>> On 11/13/2015 07:40 PM, Felipe Balbi wrote: >>>>> >>>>> Hi, >>>>> >>>>> Grygorii Strashko writes: >>>>>> On 11/13/2015 06:43 PM, Felipe Balbi wrote: >>>>>>> >>>>>>> Hi, >>>>>>> >>>>>>> Grygorii Strashko writes: >>>>>>>> Now the System stall is observed on TI AM437x based board >>>>>>>> (am437x-gp-evm) during resuming from System suspend when ARM Global >>>>>>>> timer is selected as clocksource device - SysRq are working, but >>>>>>>> nothing else. The reason of stall is that ARM Global timer loses its >>>>>>>> contexts. >>>>>>>> >>>>>>>> The reason of stall is that ARM Global timer loses its contexts during >>>>>>>> System suspend: >>>>>>>> GT_CONTROL.TIMER_ENABLE = 0 (unbanked) >>>>>>>> GT_COUNTERx = 0 >>>>>>>> >>>>>>>> Hence, update ARM Global timer driver to reflect above behaviour >>>>>>>> - save GT_CONTROL.TIMER_ENABLE during suspend and restore on resume; >>>>>>>> - ensure clocksource and clockevent devices have coresponding flags >>>>>>>> (CLOCK_SOURCE_SUSPEND_NONSTOP and CLOCK_EVT_FEAT_C3STOP) set >>>>>>>> depending on presence of "always-on" DT property. >>>>>>>> >>>>>>>> CC: Arnd Bergmann >>>>>>>> Cc: John Stultz >>>>>>>> Cc: Felipe Balbi >>>>>>>> Cc: Tony Lindgren >>>>>>>> Signed-off-by: Grygorii Strashko >>>>>>>> --- >>>>>>>> drivers/clocksource/arm_global_timer.c | 23 +++++++++++++++++++++++ >>>>>>>> 1 file changed, 23 insertions(+) >>>>>>>> >>>>>>>> diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c >>>>>>>> index a2cb6fa..1bbaf64 100644 >>>>>>>> --- a/drivers/clocksource/arm_global_timer.c >>>>>>>> +++ b/drivers/clocksource/arm_global_timer.c >>>>>>>> @@ -51,6 +51,8 @@ static void __iomem *gt_base; >>>>>>>> static unsigned long gt_clk_rate; >>>>>>>> static int gt_ppi; >>>>>>>> static struct clock_event_device __percpu *gt_evt; >>>>>>>> +static bool gt_always_on; >>>>>>>> +static u32 gt_control; >>>>>>>> >>>>>>>> /* >>>>>>>> * To get the value from the Global Timer Counter register proceed as follows: >>>>>>>> @@ -168,6 +170,9 @@ static int gt_clockevents_init(struct clock_event_device *clk) >>>>>>>> { >>>>>>>> int cpu = smp_processor_id(); >>>>>>>> >>>>>>>> + if (!gt_always_on) >>>>>>>> + clk->features |= CLOCK_EVT_FEAT_C3STOP; >>>>>>>> + >>>>>>>> clk->name = "arm_global_timer"; >>>>>>>> clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | >>>>>>>> CLOCK_EVT_FEAT_PERCPU; >>>>>>>> @@ -195,12 +200,25 @@ static cycle_t gt_clocksource_read(struct clocksource *cs) >>>>>>>> return gt_counter_read(); >>>>>>>> } >>>>>>>> >>>>>>>> +static void gt_suspend(struct clocksource *cs) >>>>>>>> +{ >>>>>>>> + gt_control = readl(gt_base + GT_CONTROL); >>>>>>>> +} >>>>>>>> + >>>>>>>> +static void gt_resume(struct clocksource *cs) >>>>>>>> +{ >>>>>>>> + /* enables timer on all the cores */ >>>>>>>> + writel(gt_control & GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL); >>>>>>> >>>>>>> do you really need to save context if all you restore is TIMER_ENABLE >>>>>>> bit ? seems like you could skip gt_suspend altogether. Is there really a >>>>>>> situation where this driver is running and GT isn't enabled ? >>>>>> >>>>>> Now It's not. It's always enabled. I did it because .suspend() is called for >>>>>> all registered clock sources regardless of their usage. So, potentially >>>>>> in the future, at the moment when .suspend() is called it might be disabled >>>>>> (for example, .enable/disable() callbacks can be added and, if ARM Global timer >>>>>> will not be registered as sched_clock, it will be possible to keep it disabled >>>>>> if not used now). >>>>>> >>>>>> But It's not essentially now - I can update it and drop save restore. >>>>>> Pls, confirm. >>>>> >>>>> I think it's best to skip suspend completely. You're not restoring >>>>> anything you saved during suspend, unless you meant | where you used &. >>>>> >>>> >>>> I didn't get it - I'm restoring one bit(0) only. >>> >>> that's the point, if you know you're restoring only that bit. Why save >>> anything at all ? >>> >> >> i think there are difference between "restoring" and "re-enabling". >> "restoring" - assume saving smth.. then restore saving value. >> I'm saving & restoring one bit here. > > with your current suspend/resume, they are the same thing. You save > GT_CONTROL contents, timer goes off and looses context, you set ENABLE > bit. No difference what so ever. > I'm writing: gt_control & GT_CONTROL_TIMER_ENABLE, where gt_control is old value of GT_CONTROL before entering suspend, so on resume: - if gt_control == 0x0000 0001 ==> gt_control & GT_CONTROL_TIMER_ENABLE(0x1) == 0x1 - if gt_control == 0x0000 0000 ==> gt_control & GT_CONTROL_TIMER_ENABLE(0x1) == 0x0 What am I missed? -- regards, -grygorii -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/