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

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Message-ID: <553A47D3.2070107@ti.com>
Date:	Fri, 24 Apr 2015 16:40:35 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Pavel Machek <pavel@....cz>, Archit Taneja <architt@...eaurora.org>
CC:	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

On 24/04/15 16:29, Pavel Machek wrote:
> 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?

The old way worked fine, afaik, so maybe we can revert. But still, isn't
it more correct to use memcpy_fromio? It's (possibly) io memory we have
here.

 Tomi



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