Passing devicetree to kernel

Passing devicetree to kernel

[Raj Swaminathan]

Hi,

The barebox documentation is a little vague on how the internal device
tree is actually passed to the kernel.  I was previously using this
environment setting to pass the kernel's devicetree to the kernel:
global.bootm.oftree=${PATH}/devicetree

My understanding was taking out that line would be sufficient.
Unfortunately I can no longer get my kernel to boot. It stalls here:

Loading ARM Linux zImage '/boot/linux'
commandline:  console=ttyS0,115200 earlyprintk  root=LABEL=root rw rootwait

Any help is appreciated.

Thanks,
Raj

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Re: Passing devicetree to kernel

[Lucas Stach]

Hi Raj,

Am Mittwoch, den 12.08.2015, 10:21 -0700 schrieb Raj Swaminathan:
> Hi,
> 
> The barebox documentation is a little vague on how the internal device
> tree is actually passed to the kernel.  I was previously using this
> environment setting to pass the kernel's devicetree to the kernel:
> global.bootm.oftree=${PATH}/devicetree
> 
> My understanding was taking out that line would be sufficient.
> Unfortunately I can no longer get my kernel to boot. It stalls here:
> 
> Loading ARM Linux zImage '/boot/linux'
> commandline:  console=ttyS0,115200 earlyprintk  root=LABEL=root rw rootwait
> 
Can you be more specific? What's the system/architecture you are using?
Which version of barebox is this and which kernel version are you trying
to start?

Regards,
Lucas
-- 
Pengutronix e.K.             | Lucas Stach                 |
Industrial Linux Solutions   | http://www.pengutronix.de/  |


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Re: Passing devicetree to kernel

[Raj Swaminathan]

Hi Lucas,

I am using Altera's cyclone 5 SoCFPGA.

Barebox version 2015.04.0
Linux is rocketboards version 3.18.0

I put some debug statements into the code at common/bootm.c and found
that the internal device tree is being used and it is the right
version. The problem is probably in the way I'm manipulating the
devicetree in barebox. I'm trying to enable some devices and fill up
the mac address field in barebox before i hand off the same devicetree
to the kernel.  One way i have gotten around the problem is to keep 2
versions of the devicetree but have barebox open the kernel devicetree
file and modify it.

Best,
raj











On Thu, Aug 13, 2015 at 8:39 AM, Lucas Stach <l.stach@pengutronix.de> wrote:
> Hi Raj,
>
> Am Mittwoch, den 12.08.2015, 10:21 -0700 schrieb Raj Swaminathan:
>> Hi,
>>
>> The barebox documentation is a little vague on how the internal device
>> tree is actually passed to the kernel.  I was previously using this
>> environment setting to pass the kernel's devicetree to the kernel:
>> global.bootm.oftree=${PATH}/devicetree
>>
>> My understanding was taking out that line would be sufficient.
>> Unfortunately I can no longer get my kernel to boot. It stalls here:
>>
>> Loading ARM Linux zImage '/boot/linux'
>> commandline:  console=ttyS0,115200 earlyprintk  root=LABEL=root rw rootwait
>>
> Can you be more specific? What's the system/architecture you are using?
> Which version of barebox is this and which kernel version are you trying
> to start?
>
> Regards,
> Lucas
> --
> Pengutronix e.K.             | Lucas Stach                 |
> Industrial Linux Solutions   | http://www.pengutronix.de/  |
>

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Re: Passing devicetree to kernel

[Lucas Stach]

Am Donnerstag, den 13.08.2015, 09:58 -0700 schrieb Raj Swaminathan:
> Hi Lucas,
> 
> I am using Altera's cyclone 5 SoCFPGA.
> 
> Barebox version 2015.04.0
> Linux is rocketboards version 3.18.0
> 
Barebox is using the mainline kernel DTs, I don't know if the downstream
Rocketboards kernel is able to work with them. I suppose there are some
incompatible changes in downstream.
But I'm not really an expert for SocFPGA, maybe Steffen can provides
some clues here.

If you want to use the builtin DT your best bet is to use a mainline
kernel.

Regards,
Lucas
-- 
Pengutronix e.K.             | Lucas Stach                 |
Industrial Linux Solutions   | http://www.pengutronix.de/  |


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Re: Passing devicetree to kernel

[Steffen Trumtrar]

Hi!

On Thu, Aug 13, 2015 at 09:58:51AM -0700, Raj Swaminathan wrote:
> Hi Lucas,
> 
> I am using Altera's cyclone 5 SoCFPGA.
> 
> Barebox version 2015.04.0
> Linux is rocketboards version 3.18.0
> 

Why are you using exactly these versions? Just curious.

> I put some debug statements into the code at common/bootm.c and found
> that the internal device tree is being used and it is the right
> version. The problem is probably in the way I'm manipulating the
> devicetree in barebox. I'm trying to enable some devices and fill up
> the mac address field in barebox before i hand off the same devicetree
> to the kernel.  One way i have gotten around the problem is to keep 2
> versions of the devicetree but have barebox open the kernel devicetree
> file and modify it.
> 

The linux clkdriver can't handle the internal devicetree from barebox and
hangs. See the patches I just posted. It works with v2015.08.0 and 4.2-rc6.
What really breaks the linux boot is the mpu_periph_clk, though. It is
marked as gate-clk but doesn't have one specified, resulting in a NULL
pointer.

Regards,
Steffen

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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