linux-kernel - Re: [PATCH] iommu: exynos: pointers are nto physical addresses

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Message-ID: <26472865.zD5Ep58Exn@wuerfel>
Date:	Mon, 29 Feb 2016 10:54:49 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
Cc:	Joerg Roedel <jroedel@...e.de>, Joerg Roedel <joro@...tes.org>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	linux-arm-kernel@...ts.infradead.org,
	iommu@...ts.linux-foundation.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu: exynos: pointers are nto physical addresses

On Monday 29 February 2016 10:33:59 Marek Szyprowski wrote:
> > ---
> > I also see that some incorrect __raw_writel() calls have crept in
> > around the same time, which breaks running big-endian kernels when
> > this driver is loaded.
> >
> > Please fix and that that as well.
> 
> Okay, so in the driver code all __raw_writel should be replaced by
> writel(), right?

Yes, writel() is always the safe choice if you don't know what to
use. __raw_writel() should be considered an implementation detail
and not used in drivers at all. There is also writel_relaxed(),
which is faster than writel() because it leaves out all the
barriers (as __raw_writel does too), and you can sometimes use that
in the fast path if you can prove that no barriers are needed.

	Arnd