linux-kernel - Re: [PATCH 4/10] atyfb: set FBINFO_READS

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Date:	Thu, 23 Jan 2014 14:31:01 -0500 (EST)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/10] atyfb: set FBINFO_READS_FAST



On Thu, 23 Jan 2014, Linus Torvalds wrote:

> Hmm. You're doing this for Matrix and now the aty driver.
> 
> Maybe the problem is at the fbcon level? Depending on
> FBINFO_READS_FAST to decide whether you should scroll or rewrite
> sounds a bit silly: even if a device doesn't have fast reads, maybe it
> has a fast accelerated BLIT operation and scrolls quickly. Should the
> fbcon test perhaps be for FBINFO_READS_FAST _or_ the
> FBINFO_HWACCEL_COPYAREA bits?

Both mach64 and matrox have a hardware bitter that is faster than 
rewriting the console - that's why FBINFO_READS_FAST improves performance 
for them.

One could improve generic framebuffer core to benchmark the performance of 
scrolling using blitter and rewrite and select FBINFO_READS_FAST 
automatically...

Mikulas

> I dunno. I didn't actually check the ->bcopy implementations, maybe
> they don't use copyarea. So I'm just going by a general "this feels
> wrong" feeling..
> 
>                 Linus


> On Thu, Jan 23, 2014 at 10:18 AM, Mikulas Patocka <mpatocka@...hat.com> wrote:
> > Set FBINFO_READS_FAST so that the console code uses scrolling instead of
> > rewriting. This improves scrolling speed.
> 
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