[U-Boot-Users] MMU setup in u-boot
Hi,
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)?
Thanks
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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)?
You did not specify which processor, but in any case, the answer can be found in your processor manaul. For example, for the 603e core, found in many Motorola embedded PowerPC processors, you cannot access more than 256 MB using a single BAT register. I believe this is a PowerPC architectural limitation. However, you might be able to juggle your system resources/configuration to use more than one BAT for mapping in memory. There are four pairs of BAT registers used for translating data accesses, and another four pairs for instruction accesses. See "PowerPC Microprocessor Family: The Programming Environments" (the green book) and your processor manual for details.
Regards,
Chris Hallinan DS4.COM, Inc.
In message NEBBKJPFOLJNBMFNKBIIAEBFDHAA.clh@net1plus.com Chris Hallinan wrote:
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)?
You did not specify which processor, but in any case, the answer can be found in your processor manaul. For example, for the 603e core,
For PowerPC boards please see the CONFIG_VERY_BIG_RAM config option as used by the sacsng board.
[John, please consider getting a different email address. We're blocking all mail from hotmail.com, so if Chris had not replied to your message I would never have seen it.]
Best regards,
Wolfgang Denk
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).
Robert
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.
participants (4)
-
Chris Hallinan -
john ashfield -
Robert Schwebel -
Wolfgang Denk