linux-kernel - Re: [RFC 00/17] clk: Add per-controller locks to fix deadlocks

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Date:   Fri, 19 Aug 2016 15:31:08 -0400
From:   Javier Martinez Canillas <javier@....samsung.com>
To:     Krzysztof Kozlowski <k.kozlowski@...sung.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Stephen Warren <swarren@...dotorg.org>,
        Lee Jones <lee@...nel.org>, Eric Anholt <eric@...olt.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Kukjin Kim <kgene@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Mark Brown <broonie@...nel.org>, linux-clk@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org, linux-i2c@...r.kernel.org,
        alsa-devel@...a-project.org
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
        a.hajda@...sung.com,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [RFC 00/17] clk: Add per-controller locks to fix deadlocks

Hello Krzysztof,

On 08/16/2016 09:34 AM, Krzysztof Kozlowski wrote:
> Hi,
> 
> RFC, please, do not apply, maybe except patch #1 which is harmless.
> 
> 
> Introduction
> ============
> The patchset brings new entity: clock controller representing a hardware
> block.  The clock controller comes with its own prepare lock which
> is used then in many places.  The idea is to fix the deadlock mentioned
> in commit 10ff4c5239a1 ("i2c: exynos5: Fix possible ABBA deadlock by keeping
> I2C clock prepared") and commit 34e81ad5f0b6 ("i2c: s3c2410: fix ABBA deadlock
> by keeping clock prepared").
> 
> 

I'm not familiar enough with the common clock framework to do a proper review
of this patch-set, but I've tested both on an Exynos5800 Peach Pi Chromebook
and an Exynos5422 Odroid XU4 board and I didn't find any clock regressions.

Also, I confirmed that the possible deadlock in the Odroid XU4 that was fixed
by reverted commit 10ff4c5239a1 doesn't happen anymore with your patches.

Tested-by: Javier Martinez Canillas <javier@....samsung.com>

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America