linux-kernel - Re: [PATCH v2 2/2] memory: samsung: exynos5422-dmc: Add module param to control IRQ mode

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Message-ID: <db571467-48ec-8f11-de1d-00393d8aa99b@samsung.com>
Date:   Mon, 3 Aug 2020 17:30:30 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org
Cc:     willy.mh.wolff.ml@...il.com, k.konieczny@...sung.com,
        cw00.choi@...sung.com, b.zolnierkie@...sung.com, krzk@...nel.org,
        chanwoo@...nel.org, myungjoo.ham@...sung.com,
        kyungmin.park@...sung.com, s.nawrocki@...sung.com, kgene@...nel.org
Subject: Re: [PATCH v2 2/2] memory: samsung: exynos5422-dmc: Add module
 param to control IRQ mode

Hi Lukasz,

On 10.07.2020 21:11, Lukasz Luba wrote:
> The driver can operate in two modes relaying on devfreq monitoring
> mechanism which periodically checks the device status or it can use
> interrupts when they are provided by loaded Device Tree. The newly
> introduced module parameter can be used to choose between devfreq
> monitoring and internal interrupts without modifying the Device Tree.
> It also sets devfreq monitoring as default when the parameter is not set
> (also the case for default when the driver is not built as a module).
>
> Reported-by: Willy Wolff <willy.mh.wolff.ml@...il.com>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>

I've got back from my holidays and noticed that in meantime this commit 
got merged as commit 4fc9a0470d2d. It revealed that there is a race 
between registering exynos5422-dmc driver and exynos-ppmu driver, which 
can be observed sometimes as the following message and freeze on Odroid 
XU3 with multi_v7_defconfig:

[    8.767708] exynos5-dmc 10c20000.memory-controller: couldn't probe 
performance counters

I will check this later why the EPROBE_DEFER error is not properly 
propagated and why it causes a freeze.

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