Problem in getting shared memory access on P1022RDK

Arshad, Farrukh Farrukh_Arshad at
Tue Jan 3 20:42:39 EST 2012

Adding more to it,

When I write from Core 1 on the shared memory region it is visible at Core 0 and it can read what I have written from Core 1 but when I write from Core 0 on this shared memory it is not visible on Core 1.

Farrukh Arshad

From: Arshad, Farrukh
Sent: Tuesday, January 03, 2012 12:11 AM
To: linuxppc-dev at
Subject: Problem in getting shared memory access on P1022RDK

Greetings All,

Please excuse me for a 'not very precise' question but I just need some clue or point to look for the trouble.
I am running linux in AMP configuration on P1022RDK dual core. My memory partitioning is given below

Core Base Address (CONFIG_PHYSICAL_START / bootm_low)
Size (bootm_size / mem kernel boot parameter)
Core 0 0x0000,0000
Core 1 0x1000,0000
Shared Memory 0x1C00,0000

I have set bootm_low / bootm_size and provided mem parameter in both kernel configurations, both
kernels are booting up fine. I have a shared memory driver running in both cores. My shared memory
driver just exposes the physical memory (0x1C00,0000) to user-space.

The problem I am facing is I can not get access to same shared memory in user-space on both kernels.
I have verified my shared memory driver on another platform (p1022ds) and it works perfect. I have also
tried using non-cached memory mapping in shared memory driver but that does not work as well.

To me it seems one of my kernels is going beyond its defined memory partition (which I have set above), I have
set kernel's partitioning as CONFIG_PHYSICAL_START, bootm_size, bootm_low and mem kernel boot param.

Besides the shared memory driver, can anyone suggest or give me clue where should I look for the
trouble in the kernel.

Farrukh Arshad.
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