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Alejandro Cabrera | 29 Apr 2011 21:45
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[microblaze-linux] BRAM Kernel Usage in recent kernels

Hi

Do anyone know if kernel code/data are placed into BRAMs after booting ? 
I want to know what is the kernel minimum BRAM memory requirement.

Kernel 2.6.20 (petalinux-0.4-final) has config parameters that allow the 
kernel BRAM usage, but in recent kernels, >= 2.6.31 I dont see it. Even 
I found a patch at mainline that allow system without BRAM at all....

What are the reason to remove the config parameters ??

best regards
Alejandro

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Steven J. Magnani | 29 Apr 2011 22:05

Re: [microblaze-linux] BRAM Kernel Usage in recent kernels

On Fri, 2011-04-29 at 15:45 -0400, Alejandro Cabrera wrote:
> Hi
> 
> Do anyone know if kernel code/data are placed into BRAMs after booting ? 
> I want to know what is the kernel minimum BRAM memory requirement.
> 
> Kernel 2.6.20 (petalinux-0.4-final) has config parameters that allow the 
> kernel BRAM usage, but in recent kernels, >= 2.6.31 I dont see it. Even 
> I found a patch at mainline that allow system without BRAM at all....
> 
> What are the reason to remove the config parameters ??
> 
> best regards
> Alejandro
> 

Hi Alejandro -

I believe the PetaLinux kernels were long a fork of an increasingly
ancient uClinux kernel. I don't think it's a question of removing
BRAM-related config parameters, so much as a decision not to port them
from PetaLinux to mainline during the 2.6.30 Microblaze merge. AFAIK
mainline Microblaze kernels don't make any use of BRAM.

Regards,
------------------------------------------------------------------------
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Michal Simek | 1 May 2011 09:18
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Re: [microblaze-linux] BRAM Kernel Usage in recent kernels

Steven J. Magnani wrote:
> On Fri, 2011-04-29 at 15:45 -0400, Alejandro Cabrera wrote:
>> Hi
>>
>> Do anyone know if kernel code/data are placed into BRAMs after booting ? 
>> I want to know what is the kernel minimum BRAM memory requirement.
>>
>> Kernel 2.6.20 (petalinux-0.4-final) has config parameters that allow the 
>> kernel BRAM usage, but in recent kernels, >= 2.6.31 I dont see it. Even 
>> I found a patch at mainline that allow system without BRAM at all....

Some kernel parts were moved to the BRAM to speedup networking and maybe others 
but it can't go to the mainline because it is just hack.

The second mainline patch is for people who want to completely remove bram. Main 
memory is place from address 0x0 and there is necessary do some things to 
support it. That's why there is this option.

>>
>> What are the reason to remove the config parameters ??

just hack which is not acceptable for mainline.

>>
>> best regards
>> Alejandro
>>
> 
> Hi Alejandro -
>
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