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Re: cacheflush system call-MIPS

To:, Ralf Baechle <>
Subject: Re: cacheflush system call-MIPS
From: David Daney <>
Date: Tue, 17 Feb 2009 09:06:32 -0800
In-reply-to: <Pine.LNX.4.58.0902150312460.459@Indigo2.Peter>
Original-recipient: rfc822;
References: <> <> <Pine.LNX.4.58.0902140002180.408@Indigo2.Peter> <> <Pine.LNX.4.58.0902150312460.459@Indigo2.Peter>
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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.

David Daney

kind regards

On Fri, 13 Feb 2009, Ralf Baechle wrote:

Date: Fri, 13 Feb 2009 23:56:03 +0000
From: Ralf Baechle <>
To: peter fuerst <>
Cc: naresh kamboju <>,
Subject: Re: cacheflush system call-MIPS

On Sat, Feb 14, 2009 at 12:50:46AM +0100, peter fuerst wrote:

there is one more good reason to ... : the Impact Xserver needs to do
a cacheflush(a,w,DCACHE) as part of the refresh-sequence.
And hence requires a sys_cacheflush, let's say, more conforming to the
man-page (or some disgusting new ioctl in the Impact kernel-driver to
do an equivalent operation ;-)
Why does it need that flush?


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