linux-kernel - Re: [PATCH 1/3] PM / Runtime: Add notifiers for device runtime PM events

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Message-id: <8bc9aa9f-f42c-3c1b-b949-c2caf2f2a270@samsung.com>
Date:	Fri, 17 Jun 2016 08:24:23 +0200
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	"Rafael J. Wysocki" <rafael@...nel.org>
Cc:	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
	linux-samsung-soc@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Joerg Roedel <joro@...tes.org>,
	Inki Dae <inki.dae@...sung.com>, Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 1/3] PM / Runtime: Add notifiers for device runtime PM
 events

Hi Rafael,


On 2016-06-08 19:18, Rafael J. Wysocki wrote:
> On Wed, Jun 8, 2016 at 12:25 PM, Marek Szyprowski
> <m.szyprowski@...sung.com>  wrote:
>> From: Krzysztof Kozlowski<k.kozlowski@...sung.com>
>>
>> Allow drivers registering for certain runtime PM events of other
>> devices. Some drivers in power domain are more or less coupled. When one
>> driver is suspending (thus leading to power domain being also turned
>> off) the other might have to perform some necessary steps. For example
>> Exynos IOMMU has to save its context.
>>
>> Based on previous work of Sylwester Nawrocki<s.nawrocki@...sung.com>.
>>
>> Signed-off-by: Krzysztof Kozlowski<k.kozlowski@...sung.com>
>> Signed-off-by: Marek Szyprowski<m.szyprowski@...sung.com>
> No, this is not the right way to address this and using notifiers for
> that is just wrong (because of the potential ordering issues).
>
> Also, the problem is not limited to runtime PM, but also to system
> suspend/resume and initialization/shutdown.
>
> I posted a series of device dependencies patches a few months ago that
> might help to address this problem, but there was almost no interest
> in it at that time.

I spent some time digging for your patches. Sadly no list archives had
them all and I finally found them only in the linux-pm patchwork. This
may explain why there was almost no interest in them.

After some debugging I've managed to get it working for my case. I will
include your patches in my v2 patchset together with the fixes needed to
get it working.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland