RE: [U-Boot-Users] MMU setup in u-boot

12 May 2003


      ...
On Mon, May 12, 2003 at 11:23:55AM -0230, john ashfield wrote:
...
u-boot setups MMU for maximum of 256M memory using Block Address
Translation. Do you have any idea how to setup MMU for
more than 256M
...
(for example 1G of memory)?
Hmm, normally the MMU is not used in U-Boot at all! This
should be the
task of the kernel (or whatever you boot).
Actually, I/DBATS *are* part of the MMU.  :) They are simply *one*
of the translation mechanisms provided by the PPC architecture!!
The MMU is enabled in start.S for 824x like this:
/*
     * Setup BATs - cannot be done in C since we don't have a stack yet
     */
    bl	setup_bats
/* Enable MMU.
     */
    mfmsr	r3
    ori	r3, r3, (MSR_IR | MSR_DR)
    mtmsr	r3
Regards,
Chris Hallinan
DS4.COM, Inc.