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Re: cacheflush system call-MIPS

To: David Daney <>
Subject: Re: cacheflush system call-MIPS
From: Eugene Surovegin <>
Date: Tue, 17 Feb 2009 11:45:09 -0800
Cc:, Ralf Baechle <>,
In-reply-to: <>
Original-recipient: rfc822;
References: <> <> <Pine.LNX.4.58.0902140002180.408@Indigo2.Peter> <> <Pine.LNX.4.58.0902150312460.459@Indigo2.Peter> <>
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.


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