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

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Date:	Fri, 24 Apr 2015 15:29:23 +0200
From:	Pavel Machek <pavel@....cz>
To:	Archit Taneja <architt@...eaurora.org>
Cc:	Tomi Valkeinen <tomi.valkeinen@...com>,
	Geert Uytterhoeven <geert@...ux-m68k.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>,
	shc_work@...l.ru, linux@....linux.org.uk,
	hsweeten@...ionengravers.com
Subject: Re: simple framebuffer slower by factor of 20, on socfpga (arm)
 platform

Hi!

On Fri 2015-04-10 12:35:52, Archit Taneja wrote:
> >That said, if the fb is in RAM, and is only written by the CPU, I think
> >a normal memcpy() for fb_memcpy_fromfb() should be fine...
> 
> I didn't test for performance regressions when I posted this patch.
> 
> A look at _memcpy_fromio in arch/arm/kernel/io.c shows that readb() is used
> all the time, even when the source and destination addresses are aligned for
> larger reads to be possible. Other archs seem to use readl() or readq() when
> they can. Maybe that makes memcpy_fromio slower than the implementation of
> memcpy on arm?

Ok, can you prepare a patch for me to try? Or should we just revert
the original commit?
									Pavel
-- 
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