Okay here is the situation,
I have hacked & slashed the PPCBoot code to work with our custom
board (all except the flash portion). I have mapped the memory as show below.
address size name BR#/OR# buswidth
0x00000000 8meg Bank0 1 32
0x00800000 8meg Bank1 2 32
0x40000000 2meg Flash0 0 16
0x60000000* 2meg Flash1 3 16
0xFFF00000 whatever IMMR N/A N/A
(* Note will be remapped to the end of flash0 to form contigious flash block
when I get around to hacking the flash code)
I have taken the "include/asm/mbx.h" and replaced its boardinfo
structure with the one I used in the PPCBoot code and then compiled the
kernel. Following the instructions in the readme file, I grabbed
arch/ppc/coffboot/vmlinux.gz and converted as shown. It is given a load
address of 0x00000000 and an entry point 0x0000000C. I put the converted
image into flash using our ICE at address 0x40020000.
Our board boots up checks the kernels CRC then uncompresses it. It
then jumps to 0x0000000C. A little bit later it then jumps to some address
0xC000???? and faults.
Is this what it is supposed to do? Am I supossed to have the RAM
mapped at 0xC0000000? If it loads at address 0 how do I remap it to
0xC0000000 once the kernel starts? Is there any way to force the kernel to
run in lower memory?
Thanks in advance for any help.
Conn Clark
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
From: Frank Smith <hidden> Date: 2000-08-19 02:10:44
-----Original Message-----
From: owner-linuxppc-embedded@lists.linuxppc.org
[mailto:owner-linuxppc-embedded@lists.linuxppc.org]On Behalf Of
clark@esteem.com
Sent: Friday, August 18, 2000 9:49 PM
To: linuxppc-embedded@lists.linuxppc.org
Subject: PPCBoot memory mapping problems
...
Our board boots up checks the kernels CRC then uncompresses it. It
then jumps to 0x0000000C. A little bit later it then jumps to some address
0xC000???? and faults.
Is this what it is supposed to do? Am I supossed to have the RAM
Jump to 0xC000???? Yup. Fault? No.
mapped at 0xC0000000? If it loads at address 0 how do I remap it to
0xC0000000 once the kernel starts? Is there any way to force the kernel to
Basically, the kernel boot process should be doing this *for* you.
Part of the kernel boot process is to set up a memory mapping from
virtual C0000000 to physical 00000000, and then enable address translation.
This is done in arch/ppc/kernel/head.S using the BAT registers.
From: Jerry Van Baren <hidden> Date: 2000-08-21 11:24:18
At 05:45 PM 8/18/00 -0700, clark@esteem.com wrote:
Okay here is the situation,
I have hacked & slashed the PPCBoot code to work with our custom
board (all except the flash portion). I have mapped the memory as show
below.
address size name BR#/OR# buswidth
0x00000000 8meg Bank0 1 32
0x00800000 8meg Bank1 2 32
0x40000000 2meg Flash0 0 16
0x60000000* 2meg Flash1 3 16
0xFFF00000 whatever IMMR N/A N/A
(* Note will be remapped to the end of flash0 to form contigious flash
block
when I get around to hacking the flash code)
One thing that leaps out at me which could be a problem, depending on
conditions and code, is the IMMR address. We found it much easier to
just set the IMMR to 0xF0000000 rather than fight the code to put it
elsewhere. Theoretically, it can be anywhere above the virtual address
of RAM (0xC0000000). You also have to be _very_ careful in your IMMR
remap code that it only is executed _once_. If you execute it a second
time or try to remap it but don't have the correct current IMMR address
(you need the current IMMR address in order to set it to the new
address), you will (probably) cause a bus fault and Bad Things Will Happen.
It shouldn't be a problem, but I would strongly urge you to _not_ set
the IMMR to 0xFFF00000 because that is the magic boot address. It will
be very confusing for everybody who follows in your footsteps as to why
you appear to be overwriting your boot code when you do IMMR I/O. I
would recommend you use one of the power up selectable IMMR addresses
(0xF0000000 is the only one that is above 0xC0000000) and it is easier
if you set your boot configuration to set the IMMR to 0xF0000000 on
bootup to make it match the linux expectations.
Another possibility is your flash addresses. The kernel makes
assumptions that the addresses of I/O is higher than the end of virtual
RAM: if your kernel is using the flash[01], it may be getting confused.
This is what Jon Diekema and I came up with for Linux memory mapping
rules, applied to mapping the resource on the EST SBC8260 board.
* EST SBC8260 Linux memory mapping rules:
Initial conditions:
-------------------
Tasks that need to be perform by the boot ROM before control is
transferred to zImage (compressed Linux kernel):
- Define the IMMR to 0xf0000000
- Initialize the memory controller so that RAM is available at
physical address 0x00000000. On the SBC8260 is this 16M (64M)
SDRAM.
- Build the board information structure (see
include/asm-ppc/est8260.h for its definition)
- The compressed Linux kernel (zImage) contains a bootstrap
loader
that is position independent; you can load it into any RAM,
ROM or FLASH memory address >= 0x00200000 (above 2 MB).
Note: If zImage is loaded at its link address of 0x00400000
(4 MB),
then zImage will skip the step of moving itself to
its link address.
- Load R3 with the address of the board information structure
- Transfer control to zImage
- The Linux console port is SMC1, and the baud rate is controlled
from the bi_baudrate field of the board information structure.
On thing to keep in mind when picking the baud rate, is that
there is no flow control on the SMC ports. I would stick
with something safe and standard like 19200.
On the EST SBC8260, the SMC1 port is on the COM1 connector of
the board.
EST SBC8260 defaults:
---------------------
0x00000000-0x00FFFFFF 16M (64M) SDRAM
0xFE000000-0xFFFFFFFF 4M flash (SIMM)
0xFC000000-0xFCFFFFFF 2M flash (8 bits wide, soldered to
the board)
0x22000000-0x2200FFFF 8K EEPROM
0x04000000-0x04FFFFFF 4M local bus SDRAM (soldered to the
board)
0x21000000-0x21000000 Flash present detect (from the flash SIMM)
0x21000001-0x21000001 Switches (read) and LEDs (write)
- BATs can map 128K-256Mbytes each. There are four data BATs and
four instruction BATs. Generally the data and instruction BATs
are mapped the same.
- The chip selects can map 32K blocks and up (powers of 2)
- The SDRAM machine can handled up to 128Mbytes per chip select
- The IMMR must be set above the kernel virtual memory addresses,
which start at 0xC0000000. Otherwise, the kernel may crash as
soon as you start any threads or processes.
- Linux uses the 60x bus memory (the SDRAM DIMM) for the
communications buffers.
- RAM is at physical address 0x00000000, and gets mapped to
0xC0000000
for the kernel.
Physical addresses used by the Linux kernel:
--------------------------------------------
0x00000000-0x3FFFFFFF 1GB reserved for RAM
0xF0000000-0xF001FFFF 128K IMMR 64K used for dual port memory,
64K for 8260 registers
Logical addresses used by the Linux kernel:
-------------------------------------------
0xF0000000-0xFFFFFFFF 256M BAT0 (IMMR: dual port RAM, registers)
0xE0000000-0xEFFFFFFF 256M BAT1 (I/O space for custom boards)
0xC0000000-0xCFFFFFFF 256M BAT2 (RAM)
0xD0000000-0xDFFFFFFF 256M BAT3 (if RAM > 256MByte)
EST SBC8260 Linux mapping:
--------------------------
DBAT0, IBAT0, cache inhibited:
Chip
Memory Sel Use
--------------------- --- ---------------------------------
0xFE000000-0xFFFFFFFF CS0 4M/16M flash (SIMM)
0xFD000000-0xFDFFFFFF CS1 0M/16M Reserved for expanded SIMM
flash
0xFC000000-0xFCFFFFFF CS6 2M/16M flash (onboard)
0xFA000000-0xFABFFFFF CS4 4M/16M local bus SDRAM
0xF8010000-0xF801FFFF CS5 8K/64K EEPROM
0xF8000000-0xF800FFFF CS7 2B/64K LED, switches, flash
present detect
0xF0000000-0xF001FFFF n/a IMMR: dual port RAM, registers
DBAT1, IBAT1, cache inhibited:
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Here is the complete document from the Linux tree,
Documentation/powerpc/SBC8260_memory_mapping.txt:
Please mail me (Jon Diekema, diekema_jon@si.com or diekema@cideas.com)
if you have questions, comments or corrections.
* EST SBC8260 Linux memory mapping rules
http://www.estc.com/http://www.estc.com/products/boards/SBC8260-8240_ds.html
Initial conditions:
-------------------
Tasks that need to be perform by the boot ROM before control is
transferred to zImage (compressed Linux kernel):
- Define the IMMR to 0xf0000000
- Initialize the memory controller so that RAM is available at
physical address 0x00000000. On the SBC8260 is this 16M (64M)
SDRAM.
- The boot ROM should only clear the RAM that it is using.
The reason for doing this is to enhances the chances of a
successful post mortem on a Linux panic. One of the first
items to examine is the 16k (LOG_BUF_LEN) circular console
buffer called log_buf which is defined in kernel/printk.c.
- To enhance boot ROM performance, the I-cache can be enabled.
Date: Mon, 22 May 2000 14:21:10 -0700
From: Neil Russell [off-list ref]
LiMon (LInux MONitor) runs with and starts Linux with MMU
off, I-cache enabled, D-cache disabled. The I-cache doesn't
need hints from the MMU to work correctly as the D-cache
does. No D-cache means no special code to handle devices in
the presence of cache (no snooping, etc). The use of the
I-cache means that the monitor can run acceptably fast
directly from ROM, rather than having to copy it to RAM.
- Build the board information structure (see
include/asm-ppc/est8260.h for its definition)
- The compressed Linux kernel (zImage) contains a bootstrap loader
that is position independent; you can load it into any RAM,
ROM or FLASH memory address >= 0x00500000 (above 5 MB), or
at its link address of 0x00400000 (4 MB).
Note: If zImage is loaded at its link address of 0x00400000 (4 MB),
then zImage will skip the step of moving itself to
its link address.
- Load R3 with the address of the board information structure
- Transfer control to zImage
- The Linux console port is SMC1, and the baud rate is controlled
from the bi_baudrate field of the board information structure.
On thing to keep in mind when picking the baud rate, is that
there is no flow control on the SMC ports. I would stick
with something safe and standard like 19200.
On the EST SBC8260, the SMC1 port is on the COM1 connector of
the board.
EST SBC8260 defaults:
---------------------
Chip
Memory Sel Bus Use
--------------------- --- --- ----------------------------------
0x00000000-0x03FFFFFF CS2 60x (16M or 64M)/64M SDRAM
0x04000000-0x04FFFFFF CS4 local 4M/16M SDRAM (soldered to the board)
0x21000000-0x21000000 CS7 60x 1B/64K Flash present detect (from the flash SIMM)
0x21000001-0x21000001 CS7 60x 1B/64K Switches (read) and LEDs (write)
0x22000000-0x2200FFFF CS5 60x 8K/64K EEPROM
0xFC000000-0xFCFFFFFF CS6 60x 2M/16M flash (8 bits wide, soldered to the board)
0xFE000000-0xFFFFFFFF CS0 60x 4M/16M flash (SIMM)
Notes:
------
- The chip selects can map 32K blocks and up (powers of 2)
- The SDRAM machine can handled up to 128Mbytes per chip select
- Linux uses the 60x bus memory (the SDRAM DIMM) for the
communications buffers.
- BATs can map 128K-256Mbytes each. There are four data BATs and
four instruction BATs. Generally the data and instruction BATs
are mapped the same.
- The IMMR must be set above the kernel virtual memory addresses,
which start at 0xC0000000. Otherwise, the kernel may crash as
soon as you start any threads or processes due to VM collisions
in the kernel or user process space.
Details from Dan Malek [off-list ref] on 10/29/1999:
The user application virtual space consumes the first 2 Gbytes
(0x00000000 to 0x7FFFFFFF). The kernel virtual text starts at
0xC0000000, with data following. There is a "protection hole"
between the end of kernel data and the start of the kernel
dynamically allocated space, but this space is still within
0xCxxxxxxx.
Obviously the kernel can't map any physical addresses 1:1 in
these ranges.
Details from Dan Malek [off-list ref] on 5/19/2000:
During the early kernel initialization, the kernel virtual
memory allocator is not operational. Prior to this KVM
initialization, we choose to map virtual to physical addresses
1:1. That is, the kernel virtual address exactly matches the
physical address on the bus. These mappings are typically done
in arch/ppc/kernel/head.S, or arch/ppc/mm/init.c. Only
absolutely necessary mappings should be done at this time, for
example board control registers or a serial uart. Normal device
driver initialization should map resources later when necessary.
Although platform dependent, and certainly the case for embedded
8xx, traditionally memory is mapped at physical address zero,
and I/O devices above physical address 0x80000000. The lowest
and highest (above 0xf0000000) I/O addresses are traditionally
used for devices or registers we need to map during kernel
initialization and prior to KVM operation. For this reason,
and since it followed prior PowerPC platform examples, I chose
to map the embedded 8xx kernel to the 0xc0000000 virtual address.
This way, we can enable the MMU to map the kernel for proper
operation, and still map a few windows before the KVM is operational.
On some systems, you could possibly run the kernel at the
0x80000000 or any other virtual address. It just depends upon
mapping that must be done prior to KVM operational. You can never
map devices or kernel spaces that overlap with the user virtual
space. This is why default IMMR mapping used by most BDM tools
won't work. They put the IMMR at something like 0x10000000 or
0x02000000 for example. You simply can't map these addresses early
in the kernel, and continue proper system operation.
The embedded 8xx/82xx kernel is mature enough that all you should
need to do is map the IMMR someplace at or above 0xf0000000 and it
should boot far enough to get serial console messages and KGDB
connected on any platform. There are lots of other subtle memory
management design features that you simply don't need to worry
about. If you are changing functions related to MMU initialization,
you are likely breaking things that are known to work and are
heading down a path of disaster and frustration. Your changes
should be to make the flexibility of the processor fit Linux,
not force arbitrary and non-workable memory mappings into Linux.
- You don't want to change KERNELLOAD or KERNELBASE, otherwise the
virtual memory and MMU code will get confused.
arch/ppc/Makefile:KERNELLOAD = 0xc0000000
include/asm-ppc/page.h:#define PAGE_OFFSET 0xc0000000
include/asm-ppc/page.h:#define KERNELBASE PAGE_OFFSET
- RAM is at physical address 0x00000000, and gets mapped to
virtual address 0xC0000000 for the kernel.
Physical addresses used by the Linux kernel:
--------------------------------------------
0x00000000-0x3FFFFFFF 1GB reserved for RAM
0xF0000000-0xF001FFFF 128K IMMR 64K used for dual port memory,
64K for 8260 registers
Logical addresses used by the Linux kernel:
-------------------------------------------
0xF0000000-0xFFFFFFFF 256M BAT0 (IMMR: dual port RAM, registers)
0xE0000000-0xEFFFFFFF 256M BAT1 (I/O space for custom boards)
0xC0000000-0xCFFFFFFF 256M BAT2 (RAM)
0xD0000000-0xDFFFFFFF 256M BAT3 (if RAM > 256MByte)
EST SBC8260 Linux mapping:
--------------------------
DBAT0, IBAT0, cache inhibited:
Chip
Memory Sel Use
--------------------- --- ---------------------------------
0xF0000000-0xF001FFFF n/a IMMR: dual port RAM, registers
DBAT1, IBAT1, cache inhibited:
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