linux-mips
[Top] [All Lists]

Re: cacheflush system call-MIPS

To: David Daney <ddaney@caviumnetworks.com>
Subject: Re: cacheflush system call-MIPS
From: Eugene Surovegin <ebs@ebshome.net>
Date: Tue, 17 Feb 2009 11:45:09 -0800
Cc: post@pfrst.de, Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org
In-reply-to: <499AEE98.1010908@caviumnetworks.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <f5a7b3810902100716t2658ce95t2dcc7f85634522@mail.gmail.com> <20090211131649.GA1365@linux-mips.org> <Pine.LNX.4.58.0902140002180.408@Indigo2.Peter> <20090213235603.GA32274@linux-mips.org> <Pine.LNX.4.58.0902150312460.459@Indigo2.Peter> <499AEE98.1010908@caviumnetworks.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.16 (2007-06-09)
On Tue, Feb 17, 2009 at 09:06:32AM -0800, David Daney wrote:
> peter fuerst wrote:
>>> Why does it need that flush?
>> To prepare the update-area (in the Shadow-FB) for DMA to RE.
>
> And on systems where the root frame buffer is directly manipulated by the 
> CPU, the video system is continually using DMA to refresh the display.  A 
> cache flush can be required to eliminate transient visual glitches.

In this case using uncached fb access is the only way to avoid 
glitches - you cannot control cache line evictions. And it's usually 
faster to use uncached mappings for effectively write-only regions.

-- 
Eugene


<Prev in Thread] Current Thread [Next in Thread>