Regarding MPC8641D

Hai,
We have designed a MPC8641D based AMC card. We are using the
kernel (2.6.23-rc4) and uboot (1.2.0). When we disable the core1 Low Memory offset mode the kernel was up and when we enable this core1 Low Memory offset mode kernel was not up, It was hang after MPIC initialization.

Kerenl dump :

# Booting image at 00200000 ...

  Image Name:   Linux-2.6.23-rc4-g5326152f-dirty
  Image Type:   PowerPC Linux Kernel Image (gzip compressed)
  Data Size:    4544816 Bytes =  4.3 MB

Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Booting using flat device tree at 0x700000
data:0
Probing machine type ...
MPC86xx HPCN ...start c05d1e10 end c05d1ee0 <6>Using MPC86xx HPCN machine
description
Total memory = 600MB; using 2048kB for hash table (at cfe00000) Linux version 2.6.23-rc4-g5326152f-dirty (root@sivaji) (gcc version 4.0.2 20060628 (Wasabi)) #45 SMP Wed Dec 5 12:01:58 IST 2007
console [udbg0] enabled
setup_arch: bootmem
mpc86xx_hpcn_setup_arch()
Found FSL PCI host bridge at 0x00000000f8008000.Firmware bus number: 0->254 MPC86xx HPCN board from Freescale Semiconductor
arch: exit
Zone PFN ranges:
DMA 0 -> 153600
Normal 153600 -> 153600
Movable zone start PFN for each node
early_node_map[1] active PFN ranges
0: 0 -> 153600
Built 1 zonelists in Zone order. Total pages: 152400
Kernel command line: root=/dev/ram console=ttyS0,115200 mem=600M
mpic: Setting up MPIC " MPIC " version 1.2 at f8040000, max 2 CPUs
mpic: ISU size: 88, shift: 7, mask: 7f
mpic: Initializing for 88 sources
PID hash table entries: 4096 (order: 12, 16384 bytes)
Console: colour dummy device 80x25
Dentry cache hash table entries: 131072 (order: 7, 524288 bytes) Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
Memory: 600064k/614400k available (5832k kernel code, 14096k reserved, 116k data, 233k bss, 3244k init)
SLUB: Genslabs=22, HWalign=32, Order=0-1, MinObjects=4, CPUs=2, Nodes=1 Security Framework v1.0.0 initialized

SELinux:  Initializing.
selinux_register_security:  Registering secondary module capability

Capability LSM initialized as secondary
Mount-cache hash table entries: 512
mpic: requesting IPIs ...

After this the kernel was hang, i want to know why
kernel was hang when we enalbe Low memory Offset mode. Please help me to fix this issue.
Thanks and Regards
Sivaji

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[snip!]

Have you compiled your kernel for SMP mode? I believe the Low memory offset mode is only for AMP mode (vxworks can use this, probably other OSes). I don't know if the kernel has support for any multiprocessing mode other than SMP.

Hope that helps,
Chris

Hai,
The kernel was compiled in SMP mode. The low memory offset mode
is only for AMP mode means, then how we test both the core 0 and 1 in the linux kernel ?. Asper my understanding if we enable the Low Memory Offset mode, then only the core1 translation is enabled. If we disalbed the Low Memory offset mode, Only Core 0 will work in SMP mode and Core 1 will idle. If we want to test the efficient of Dual core means we need to enable both the core and Low Memory Offset Mode. For this configuration linux kernel was not up.
( Please correct me if I am wrong )

Thanks and Regards
Sivaji

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Hi,

If you want to use SMP, do not enable low memory offset mode. That is only and only for AMP, not for SMP. All the exception vectors go into a different address range for core1, once you enable that, resulting in a need for entirely different copy of OS (be it Linux, or any other OS).

You are in the right path. Just don't enable low memory offset mode, unless you are looking for Assymetric multi-processing.

- siva

Message: 6
Date: Wed, 5 Dec 2007 16:45:31 -0800 (PST)
From: sivaji <[email protected]>
Subject: Re: Regarding MPC8641D
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=3Dus-ascii

Hai,
The kernel was compiled in SMP mode. The low memory offset
mode
is only for AMP mode means, then how we test both the core 0 and 1 in the
linux kernel ?. Asper my understanding if we enable the Low Memory Offset
mode, then only the core1 translation is enabled. If we disalbed the Low Memory offset mode, Only Core 0 will work in SMP mode and Core 1 will idle.
If we want to test the efficient of Dual core means we need to enable both
the core and Low Memory Offset Mode. For this configuration linux kernel was
not up.
( Please correct me if I am wrong )

Thanks and Regards
Sivaji

the

Memory

why

to

Hi,
We need only SMP mode, asper ur idea let me disable the Low
memory offset mode. We face some issues when ioremap in the kernel, we guess the problem is related to Low memory offset mode so only we go for that. Consider now the Low memory offset is disable the bootargs (root=/dev/ram console=ttyS0, mem=504M). When mem=504 or greater than we are not able to ioremap, if mem is less than 500 there was no issues on ioremap. We can't understand why ioremap was failed for 504M?

Thanks and Regards
S.Balamurugan

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BTW... it is not true that core1 is idle when low memory offset mode is disabled. Taking core1 out of reset will enable core1 to start booting. These two are two different things.

- Siva

-----Original Message-----
From: Siva Prasad=20
Sent: Wednesday, December 05, 2007 5:06 PM
To: '[email protected]'
Cc: '[email protected]'
Subject: Regarding MPC8641D

Hi,

If you want to use SMP, do not enable low memory offset mode. That is only and only for AMP, not for SMP. All the exception vectors go into a different address range for core1, once you enable that, resulting in a need for entirely different copy of OS (be it Linux, or any other OS).

You are in the right path. Just don't enable low memory offset mode, unless you are looking for Assymetric multi-processing.

- siva

Message: 6
Date: Wed, 5 Dec 2007 16:45:31 -0800 (PST)
From: sivaji <[email protected]>
Subject: Re: Regarding MPC8641D
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=3Dus-ascii

Hai,
The kernel was compiled in SMP mode. The low memory offset
mode
is only for AMP mode means, then how we test both the core 0 and 1 in the
linux kernel ?. Asper my understanding if we enable the Low Memory Offset
mode, then only the core1 translation is enabled. If we disalbed the Low Memory offset mode, Only Core 0 will work in SMP mode and Core 1 will idle.
If we want to test the efficient of Dual core means we need to enable both
the core and Low Memory Offset Mode. For this configuration linux kernel was
not up.
( Please correct me if I am wrong )

Thanks and Regards
Sivaji

the

Memory

why

to