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

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Date:	Fri, 24 Apr 2015 15:31:24 +0200
From:	Pavel Machek <pavel@....cz>
To:	Arnd Bergmann <arnd@...db.de>
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,
	Archit Taneja <architt@...eaurora.org>
Subject: Re: simple framebuffer slower by factor of 20, on socfpga (arm)
 platform


> > The difference is probably caused by memcpy() vs memcpy_fromio(). The
> > comment above memcpy_fromio() says "This needs to be optimized". I think
> > generally speaking memcpy_fromio() is correct for a framebuffer.
> > 
> > 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...
> 
> Could memcpy() cause alignment traps here if the fb pointer is unaligned
> and uncached?

Original commit did not comment on any failure, so I expect that is
not a problem here...
									Pavel
-- 
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