ioremap() fails for >64 MB

Dan Malek dan at
Wed Aug 23 21:51:40 EST 2006

On Aug 23, 2006, at 6:00 AM, Phil Nitschke wrote:

> Since my (2 GB) memory is within the (4 GB) addressable by a 32-bit
> processor, why do I need high memory at all?

Because the processor used virtual memory addressing, and
we divide this 4G virtual space up among application, kernel,
IO mapping, etc.  The kernel can't map the whole 4G (or even
the 2G) physical space at one time.

> I avoided this simply because I wanted to load/unload my driver  
> (during
> development),

My personal preference is to debug drivers in a development
mode by building them into the kernel.  I find it easier to debug,
and you are also likely to be rebooting anyway :-)

	-- Dan

More information about the Linuxppc-embedded mailing list