From: Jon Smirl <jonsmirl@yahoo.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
kronos@kronoz.cjb.net,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Mapping large framebuffers into kernel space
Date: Sun, 7 Sep 2003 17:17:16 -0700 (PDT) [thread overview]
Message-ID: <20030908001716.78049.qmail@web14901.mail.yahoo.com> (raw)
In-Reply-To: <1062973512.19548.0.camel@dhcp23.swansea.linux.org.uk>
--- Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>
> The kernel has 4Gb of virtual address space. Because of the way x86
> works it really wants to keep the user map, the view of main memory and
> io mappings visible at once. For larger objects you have to use kmap and
> map them through a window (anyone remember they joys of EMS). On
> 64bit this of course all goes away
>
On my system I have 1GB physical and 1GB swap. So there should always be some
open address space in the 1-4GB kernel address space. Would it be better to map
the framebuffer to 1-4GB when HIGHMEM is configured? Is there an ioremap() that
will map to high memory? Seems that this would be better than reserving 256MB
in the 0-1GB range and forcing 256MB of physical RAM into highmem.
The kernel DRM drivers map framebuffers up to 256MB in size into user space.
Could this be mapped as a single 256MB page instead of 64K 4KB ones?
We're working on the radeon drivers right now so I can try a few things out.
=====
Jon Smirl
jonsmirl@yahoo.com
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next prev parent reply other threads:[~2003-09-08 0:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-07 21:18 Jon Smirl
2003-09-07 22:25 ` Alan Cox
2003-09-08 0:17 ` Jon Smirl [this message]
2003-09-08 12:28 ` Alan Cox
-- strict thread matches above, loose matches on Subject: below --
2003-09-07 18:21 Jon Smirl
2003-09-07 19:12 ` Alan Cox
2003-09-07 19:26 ` Zwane Mwaikambo
2003-09-07 19:42 ` Jon Smirl
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