Re: Support for ARM940T core Samsung S3C2510A MCU under Linux

[Greg Ungerer <gerg@snapgear.com>]

Hi Madhavi,

On 22/03/11 22:43, Madhavi Manchala wrote:
> Thank you very much for your valuable information and suggestions.
>
> On Mon, Mar 21, 2011 at 4:57 PM, Greg Ungerer<gerg@snapgear.com>  wrote:
>> On 19/03/11 01:54, Madhavi Manchala wrote:
>>>
>>> I have one basic question about the architecture files in Linux
>>> kernels. We have a board with Samsung S3C2510A MCU (ARM940T core)
>>> which is a no-mmu based CPU. I heard that "there was not a lot of ARM
>>> no-mmu support at the moment" from Ben Dooks.
>>
>> The core is there, but there is very little specific machine support.
>> The one I use for testing is non-MMU ARM is the Atmel/AT91X40 (that is
>> CONFIG_ARCH_AT91X40). I don't run it on real hardware, but on the
>> SkyEye emulator.
>
> I saw the mach-at91/at91x40.c and mach-at91/at91x40_time.c file
> sources. There is a few lines of code is available in these two files.
> I guess, some of the common files are there for all Atmel boards and
> that is also included as a part of at91x40 board. Am I correct?

Yes, exactly. Much of the code is shared by all type of at91 parts,
irrespective of whether they have the MMU or not. (Most of the
internal peripherals at either the same or very similar - so
things like interrupts, etc).


> I found only at91_aic_init() function only called from at91x40.c file.
> What about other initialization like serial etc.?  Is this included
> from common files for Atmel boards?

Serial is a problem for this target, it is a little different
on the old at91x40 series to most of the newer at91 parts. Currently
it requires a different driver than the standard at91 serial driver.
(And that driver is not in mainline, and is not a platform type
driver either).


>>> So, I started developing the architecture files for my Samsung
>>> S3C2510A MCU (ARM940T core) by looking at the existing S3C2410A
>>> (ARM920 core) architecture files. Is this my porting (developing the
>>> architecture files) correct?
>>
>> Would make sense to start on something similar, yes.
>
> I downloaded the latest uClinux sources from
> http://sourceforge.net/projects/uclinux/files/uClinux%20Stable/ and
> the name of the file is uClinux-dist-20101026.tar.bz2. In this
> distribution, I found mach-s3c24a0, mach-s3c3410, s3c44b0x and
> mach-s5c7375 sources in linux-2.6.x/arch/arm/ directory. (Arnd asked
> me to see these sources as a reference, only). So, I am looking at
> these sources and especially s3c3410 sources as remaining are
> different like s3c24a0 is a MMU based etc.
>
>>
>>> How can I port the Linux on to my board which has a Samsung S3C2510A
>>> MCU (ARM940T core) which is a NO-MMU based CPU?
>>>
>>> Thanks for your suggestions / hints / comments.
>>
>> You can look at what I did with the AT91X40 for an example.
>> Or look at the patches that Ithamar Adema sent to the ARM linux
>> mailing list in the last few days for supporting the NXP LPC2K
>> family as another example (they are also non-MMU parts).
>
> As I said above, there are only two files which are related to at91x40
> board. However, I found some sources for the Ithamar Adema patches at
> the following link.
> http://www.spinics.net/lists/arm-kernel/msg118932.html
>
> These sources (patches) are similar to samsung sources which are
> available in uClinux-dist. So, I will look into the Ithamar Adema
> patches and uClinux-dist samsung machine directory sources. Please
> suggest me.

Looking at all of these will be useful. The AT91 changes where quite
simple due to the high degree of similarity.


> My final question, All these samsung machines (s3c24a0, s3c3410,
> s3c44b0x and s5c7375) are ARM7TDMI core based MCUs. My MCU (Samsung
> s3c2510A) is a ARM9TDMI core based. So, is this porting will help?
>
> I am extreamly sorry, If I asked silly questions here.
>
> Once again, thanks for your suggestions and valuable inforamtion.

No problem, glad to help.

Regards
Greg


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Greg Ungerer  --  Principal Engineer        EMAIL:     gerg@snapgear.com
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