Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754223AbbFOIwd (ORCPT ); Mon, 15 Jun 2015 04:52:33 -0400 Received: from foss.arm.com ([217.140.101.70]:33949 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752168AbbFOIw0 (ORCPT ); Mon, 15 Jun 2015 04:52:26 -0400 Message-ID: <557E9244.7090106@arm.com> Date: Mon, 15 Jun 2015 09:52:20 +0100 From: Sudeep Holla User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Doug Anderson , Javier Martinez Canillas CC: Sudeep Holla , Krzysztof Kozlowski , "linux-samsung-soc@vger.kernel.org" , Jason Cooper , Chanho Park , "linux-kernel@vger.kernel.org" , Kukjin Kim , Peter Chubb , Shuah Khan , Thomas Gleixner , Tomasz Figa , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v2 1/1] irqchip: exynos-combiner: Save IRQ enable set on suspend References: <1434087795-13990-1-git-send-email-javier.martinez@collabora.co.uk> <557AB00C.5040606@arm.com> <557AC23D.8040602@collabora.co.uk> <557AC85E.5070705@arm.com> <557AD728.7090908@collabora.co.uk> <557B34A7.4090507@collabora.co.uk> In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4888 Lines: 114 On 12/06/15 21:17, Doug Anderson wrote: > Hi, > > On Fri, Jun 12, 2015 at 12:36 PM, Javier Martinez Canillas > wrote: >>>> registers are lost assuming the combiner was powered down, even the >>>> status register will be lost and you will not know exactly the wakeup >>>> reason right ? >>>> >>> >>> Good question, I didn't find in the documentation I've access to that >>> this happen but just found through experimentation that the IRQ enable >>> set register values are lost after a resume and that saving/restoring >>> the values makes the interrupts to be triggered again. >>> >> >> I'll share here too the findings I mentioned over IRC. As you suggested I >> add some printouts and noticed that the ISTRn (Interrupt Status) registers >> values are indeed preserved on resume so I can know for example if the >> wakeup source was the power gpio-key or cros_ec keyboard. I've checked the >> values of the registers against the Exynos manual and they corresponds to >> the interrupt sources in each case so the values are correct. >> >> So as you said, it seems that is not that the IP block loses its state on >> S2R but that something is blindly writing the IESRn (Interrupt Enable Set) >> registers. > > I'll postulate an alternate theory here. You can tell me if you buy > it or if you think I've been out in the sun too long. > > Let's say that the interrupt combiner's status registers show the raw > status as asserted by whatever is hooked up to the combiner. This > means that even if the combiner got reset we could still read the > status register and get the status of the source. Imagine that the > combiner is like a GPIO bank. If you reset the GPIO bank, you'll lose > all kinds of config (input vs. output, edge interrupt status, maybe > pulls, etc). ...but you can still read the state asserted by an > external source, right? > Right, this makes sense. I assumed status was latched output and might be lost. But that's wrong assumption I believe. > In this case the combiner's interrupt source is 'EINT 11'. ...and I'm > pretty sure that the controller managine 'EINT 11' _doesn't_ lose > power across suspend/resume... > > > I'll further bolster my theory by saying that _almost nothing_ in the > exynos keeps power across suspend/resume. The UART? Nope. The GPIO > controllers? Nuh-uh. The GIC? Sorry, but no. The clock tree? It > might be nice, but you're out of luck. ...so it would make me > terribly surprised to see the combiner keep power. > Interesting even GIC loses power ? I would be interested in knowing more details as who will wake up the system then. Is the wakeup source offloaded to some external power controller ? > >> To reduce the possible s/w components that could be doing this, I booted a >> signed FIT image directly using the RO U-Boot instead of chain loading a >> mainline nv-uboot. In this configuration I've the same issue so it seems >> that if something is zeroing those registers on S2R, this can't be changed >> without void the warranty of these machines. >> >> I also looked at the downstream ChromiumOS v3.8 tree [0] and I see that >> they have a very similar solution than my patch, the IESRn are also saved >> but using a notifier for the CPU_PM_ENTER and CPU_PM_EXIT events instead >> or registering a syscore ops but the idea is basically the same. > > Yup, you can see where kliegs added it in > . As per the > comments in that CL, this was probably broken in: > > 063bd6f ARM: EXYNOS: Remove GIC save & restore function > > >> I have to take a look to the U-boot that is shipped on the device, I think >> the correct branch is [1] but I'm not sure if that is the correct one. > > It is the right one. If U-Boot were touching this (which would > greatly surprise me) it should be here: > > arch/arm/include/asm/arch-exynos/cpu.h > > ...and it's not. Doing a grep for '10440000' (the combiner base > address) doesn't find anything in U-Boot either, which makes it less > likely. ...and it's even less likely since the amount of code that is > in U-Boot that runs at resume time is a very small subset and I'm > fairly familiar with it and I would have remembered it touching the > combiner. > Yes, I did search and find nothing, so definitely not U-Boot if I am looking at the right source. > It's POSSIBLE that the internal ROM in exynos is clobbering this, but > as per above it seems crazy unlikely and I think it's just losing > power. > Agreed, not because I believe ROM code are not crazy but because of the theory you have provided above :) Regards, Sudeep -- 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/