linux-kernel - Re: simple framebuffer slower by factor of 20, on socfpga (arm) platform

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Date:	Tue, 12 May 2015 10:52:53 +0200
From:	Pavel Machek <pavel@....cz>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Archit Taneja <architt@...eaurora.org>,
	Marek Vasut <marek.vasut@...il.com>,
	kernel list <linux-kernel@...r.kernel.org>,
	Dinh Nguyen <dinh.linux@...il.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Rob Clark <robdclark@...il.com>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Alexander Shiyan <shc_work@...l.ru>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>
Subject: Re: simple framebuffer slower by factor of 20, on socfpga (arm)
 platform

On Wed 2015-05-06 11:45:04, Russell King - ARM Linux wrote:
> On Tue, Apr 28, 2015 at 11:28:53AM -0400, Nicolas Pitre wrote:
> > On Tue, 28 Apr 2015, Russell King - ARM Linux wrote:
> > 
> > > On Fri, Apr 24, 2015 at 03:46:56PM +0200, Geert Uytterhoeven wrote:
> > > > So please optimize ARM's _memcpy_fromio(), _memcpy_toio(), and _memset_io().
> > > > That will benefit other drivers on ARM, too.
> > > 
> > > That's not going to happen.
> > > 
> > > I've had a patch which does that, but people are concerned that it changes
> > > the behaviour of the functions by changing the access size, which could
> > > cause regressions.  It seems people are far too worried about that to even
> > > consider trying. :(
> > 
> > What about making the optimized implementation available via kconfig?
> 
> I'd prefer not to.  My personal feeling is to put the patch in and just be
> done with it - these functions are supposed to be used on IO areas which
> don't care about access size (in other words, are memory-like rather than
> being register-like.)  Here's the rather old patch:
> 
> From: Russell King <rmk+kernel@....linux.org.uk>
> Subject: [PATCH] ARM: optimize memset_io()/memcpy_fromio()/memcpy_toio()
> 
> If we are building for a LE platform, and we haven't overriden the
> MMIO ops, then we can optimize the mem*io operations using the
> standard string functions.
> 
> Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>

Tested-by: Pavel Machek <pavel@....cz>
Acked-by: Pavel Machek <pavel@....cz>

Works for me, framebuffer performance is back in "too fast to measure"
range.

When this is merged, should 981409b25e2a99409b26daa67293ca1cfd5ea0a0
be reverted in -stable?

Thanks,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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