linux-kernel - Re: [PATCH v11 17/27] iommu/exynos: remove calls to Runtime PM API functions

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Date:	Wed, 19 Mar 2014 11:37:57 -0700
From:	Grant Grundler <grundler@...omium.org>
To:	Tomasz Figa <t.figa@...sung.com>
Cc:	Grant Grundler <grundler@...omium.org>,
	Cho KyongHo <pullip.cho@...sung.com>,
	Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	Linux DeviceTree <devicetree@...r.kernel.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	Joerg Roedel <joro@...tes.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Prathyush <prathyush.k@...sung.com>,
	Rahul Sharma <rahul.sharma@...sung.com>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Varun Sethi <Varun.Sethi@...escale.com>
Subject: Re: [PATCH v11 17/27] iommu/exynos: remove calls to Runtime PM API functions

On Wed, Mar 19, 2014 at 10:30 AM, Tomasz Figa <t.figa@...sung.com> wrote:
...
> As I said, AFAIK the trend is to get rid of ordering by initcalls and make
> sure that drivers can handle missing dependencies properly, even for
> "services" such as DMA, GPIO, clocks and so on, which after all are provided
> by normal drivers like other.

Ok - I'm not following the general kernel dev trends. initcall()
levels are easy to understand and implement. So I would not be in a
hurry to replace them.

>> ps. I've written IOMMU support for four different IOMMUs on three
>> operating systems (See drivers/parisc for two linux examples). But I
>> still feel like I at best have 80% understanding of how this one is
>> organized/works. Abstract descriptions and convoluted code have been
>> handicapping me (and lack of time to dig further).
>
>
> Well, this is one of my concerns with this driver. It isn't easy to read
> (and so review, maintain, extend and debug found issues).

My postscript comment was more to explain why I'm not confident in my
opinion - not a reason to reject the patch series.  I still consider
the whole series as a step forward. But I'm not the expert here.

Right now, with ~30 patches posted by the exynos iommu (official?)
maintainer, no one else who has a clue will attempt to fix or clean up
those kinds of problems.  i.e. it's useful to enable others to fix
what are essentially unspecified "design pattern" issues.

cheers,
grant
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