[yocto] Altera Cyclone V DTB origin

[Smith, Virgil]

Perhaps someone could improve on this, but
you can build a dtb from a source dts using a bbappend for your linux kernel.
1. drop a copy of your new dts in ${S}/arch/arm/boot/dts
2. add the name of your dtb to the KERNEL_DEVICETREE variable.

If you are modifying an existing dts file, the cleanest approach is probably to use a patch file for step 1.  However, you could also create a completely new file.  That you could add either as a patch or by a direct file copy with something like

SRC_URI += "my-device-tree.dts"
KERNEL_DEVICETREE += "my-device-tree.dtb"
do_patch_append() {
  cp ${WORKDIR}/my-device-tree.dts ${S}/arch/arm/boot/dts/
}

Using do_configure_append (or even possibly do_unpack_append) might be more appropriate and would let you easily patch your own file in another layer, but I have not personally tried that.

However, if changing the name of the dtb (i.e. adding your own), you may need to tweak your bootloader (U-boot?) to pass the right dtb to the kernel at boot.  I don't know the Altera Cyclone configuration/layers/versions so take that as a very general statement.

Also, check the kernel recipe you are extending KERNEL_DEVICETREE may need to be expressed as KERNEL_DEVICETREE_somemachinenamehere.


> -----Original Message-----
> From: yocto-bounces at yoctoproject.org [mailto:yocto-
> bounces at yoctoproject.org] On Behalf Of Steffen Schuetz
> Sent: Monday, May 18, 2015 7:13 AM
> To: yocto at yoctoproject.org
> Subject: Re: [yocto] Altera Cyclone V DTB origin
>
> Hi,
>
> I found that the dtb is obtained from a git reposirtory during the build and stored
> under build/tmp/work/socfpga_cyclone5-poky-linux-gnueabi/linux-altera-
> ltsi/3.10-r1/git/arch/arm/boot/dts/
> I succesfully build a custom dtb following these suggestions:
> https://community.freescale.com/thread/325219
>
> Is there a way to do this using a bitbake mechanism?
>
> Thanks!
>
> Best Regards,
> Steffen
>
> On 05/18/2015 11:41 AM, Steffen Schuetz wrote:
> > Hi,
> >
> > I build a customized Linux image using Yocto Daisy - we need gcc >=
> > 4.8
> > - following the instructions at
> >
> http://rocketboards.org/foswiki/Documentation/YoctoDoraBuildWithMetaAlter
> a .
> > Besides the zImage and rootfs the build process outputs an .dtb file.
> > Now, in order to get the FPGA fabric involved, I'd have to come up
> > with a modified dts and build it.
> > That's where I'm a bit lost in the blur. I can not figure out where
> > the generated dtb is coming from? What's the mechanism behind? I
> > cannot find any .dts nor .dtb in the meta-altera layer.
> >
> > Besides that I realized that if I use the dtb that shipped with the
> > board with the "daisy" kernel, the boot process gets stuck at "Waiting
> > for root device /dev/mmcblk0p3..." The "shipped" kernel is version
> > 3.8.0 while the "daisy" one is 3.10.31-ltsi.
> > Was there a change in the device tree layout as the "old" one doesn't
> > work with the "daisy" kernel?
> >
> >
> > Thanks in advance!
> >
> > Regards,
> > Steffen
>


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