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 Post subject: Porting linux4sam-4.7 to at91sam9g20
PostPosted: Fri Oct 23, 2015 10:43 am 
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I have a at91sam9g20 processor that is running linux 2.6.27. Does anyone have experience on the amount of work that would be required to port the newer kernel to that processor? I don't think that there are any major changes in the kernel to adapt it to my platform. The reason for the upgrade is that there are several new features that I'm interested in having access to, and I think that it might be comparable to port the newer kernel to the old platform and porting the features I need to the old kernel.


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 Post subject: Re: Porting linux4sam-4.7 to at91sam9g20
PostPosted: Mon Oct 26, 2015 8:34 pm 
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Joined: Thu Apr 19, 2007 10:15 pm
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Location: USA
kotte wrote:
I have a at91sam9g20 processor that is running linux 2.6.27. Does anyone have experience on the amount of work that would be required to port the newer kernel to that processor?
The AT91SAM9G20 is a SoC, not a processor.
It uses an ARM926EJ-S processor.
Since 2.6.27 the Linux kernel has supported the ARM926EJ-S processor and the AT91SAM9G20 SoC, so there is no need for you to "port the newer kernel to that processor".
You would be porting the kernel to your board.
These distinctions are not trivial, and are reflected in the directory structure of the kernel source code.

kotte wrote:
I don't think that there are any major changes in the kernel to adapt it to my platform.
SInce you think that, then why are you even asking questions?

You should not have to make any changes for the processor or SoC.
But you haven't provided any information about your board, so that's an unconfirmed assumption.
You seem to be reporting that there are no custom drivers.

ADC and GPIO are two devices that have changed over that version span.

Depending on your board's similarity to the Atmel EK evaluation board, the kernel task could be as little as a half-day effort.
Regardless, the task is simplified by knowing that a previous kernel version has worked, and you don't have the uncertainty of a prototype board.

Regards


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 Post subject: Re: Porting linux4sam-4.7 to at91sam9g20
PostPosted: Wed Oct 28, 2015 10:29 am 
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Joined: Thu Oct 22, 2015 4:00 pm
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Thanks for clarification :-)

OK, so in theory I don't need to do any changes in the kernel source code the to make the linux4sam-4.7 then? I think I was a bit confused by the fact that there isn't defconfig for the at91sam9g20, but I see now that it uses device tree files instead (yes, I have been living under a rock ;-))

Thanks


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 Post subject: Re: Porting linux4sam-4.7 to at91sam9g20
PostPosted: Wed Oct 28, 2015 8:56 pm 
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Joined: Thu Apr 19, 2007 10:15 pm
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Location: USA
kotte wrote:
OK, so in theory I don't need to do any changes in the kernel source code the to make the linux4sam-4.7 then?
Same question without adding any new information will not get you a new or different answer.


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 Post subject: Re: Porting linux4sam-4.7 to at91sam9g20
PostPosted: Thu Feb 18, 2016 12:45 am 
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Joined: Sat May 03, 2014 7:34 pm
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I've succesfully tested linux 4.4 with and without preempt-rt on an at91sam9g20 based board.

You will definitively have to write a device tree for your particular board, unless it is already present in the mainline linux tree.


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 Post subject: Re: Porting linux4sam-4.7 to at91sam9g20
PostPosted: Tue Jul 04, 2017 3:17 pm 
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abelloni wrote:
You will definitively have to write a device tree for your particular board, unless it is already present in the mainline linux tree.


That's what we did when migrating from an old 2.6.36.x kernel to a recent 4.9.x one on a at91sam9g20 based board. This and tuning your kernel config is basically the main parts to do.

However if you have some drivers which are not in mainline, you may have additional work of uncertain amount, depending on which internal kernel interfaces you used before. :wink:


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 Post subject: Re: Porting linux4sam-4.7 to at91sam9g20
PostPosted: Tue Jul 04, 2017 8:53 pm 
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Joined: Thu Jun 22, 2017 8:00 pm
Posts: 11
I am using kernel 4.1 in a SAM9G25 board and based our device tree from AT91SAM9G25EK:

Code:
<your-yocto>/poky/build-idprint/tmp/work-shared/idprint/kernel-source/arch/arm/boot/dts/atsam9g25ek.dts


Since both chips are quite close I think it would be a good start for you to take a fresh copy of newest Linux4SAM (5.6) and check this file and its inclusions to base your own DTS.

If my understanding is not that wrong, you could start a fresh DTS file including

Code:
#include "at91sam9g25.dtsi"
#include "at91sam9x5ek.dtsi"


like "atsam9g25ek.dts" does and then tweak your SoC specs (with your datasheet in hands) for a quick drive.

Hope it helps.


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