linux-kernel - Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 24 Aug 2015 15:15:44 +0200
From:	Marek Vasut <marex@...x.de>
To:	"Russell King - ARM Linux" <linux@....linux.org.uk>
Cc:	Cyrille Pitchen <cyrille.pitchen@...el.com>, mark.rutland@....com,
	devicetree@...r.kernel.org, pawel.moll@....com,
	ijc+devicetree@...lion.org.uk, ben@...adent.org.uk,
	zajec5@...il.com, nicolas.ferre@...el.com,
	linux-kernel@...r.kernel.org, robh+dt@...nel.org,
	linux-spi@...r.kernel.org, juhosg@...nwrt.org, broonie@...nel.org,
	linux-mtd@...ts.infradead.org, galak@...eaurora.org,
	shijie.huang@...el.com, computersforpeace@...il.com,
	dwmw2@...radead.org, linux-arm-kernel@...ts.infradead.org,
	beanhuo@...ron.com
Subject: Re: [PATCH linux-next v4 5/5] mtd: atmel-quadspi: add driver for Atmel QSPI controller

On Monday, August 24, 2015 at 02:49:24 PM, Russell King - ARM Linux wrote:

Hi Russell,

> On Mon, Aug 24, 2015 at 01:03:51PM +0200, Marek Vasut wrote:
> > These are functions, not macros :)
> > 
> > btw is there any reason for these ? I'd say, just put the read*() and
> > write*() functions directly into the code and be done with it, it is
> > much less confusing.
> > 
> > Also, why do you use the _relaxed() versions of the functions ?
> 
> Now that the _relaxed() accessors are available throughout the kernel,
> everyone should be using the _relaxed() versions unless they need the
> properties of the non-relaxed versions.

You mean the memory barrier, right ?

> Remember that the non-relaxed
> versions are rather expensive on ARM due to the need to go all the way
> out to the L2 cache - it at least doubles the number of accesses for
> every read*/write*().

I think in case of this driver, we don't need the non-relaxed version
anywhere, right ? Thanks for the educational writeup :)

btw. is [1] still the current study material on the I/O accessor best
practices please ?

[1] http://permalink.gmane.org/gmane.linux.ports.arm.kernel/117644

Best regards,
Marek Vasut
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/