Hello,
Moving the discussion to the project mailing list, so that it is available to all interested parties.
---------- Forwarded message --------- From: Dmitry Baryshkov dmitry.baryshkov@linaro.org Date: Wed, 15 Mar 2023 at 22:22 Subject: Re: Linaro kernel for QRB5165 To: Patrick Whewell patrick.whewell@sightlineapplications.com
Hi Patrick,
On Wed, 15 Mar 2023 at 19:17, Patrick Whewell patrick.whewell@sightlineapplications.com wrote:
Thanks for that info! That explains why I couldn't figure out how it was selecting from the dtb appened to the kernel image. We'd like to eventually be able to use the Linaro kernel on the Lantronix board for testing. I can help supply some information but I believe it is supplying the vendor files.
Lantronix provides a script that downloads and builds the kernel automatically but the relevant information is the following:
In the repo manifest this is the information for the kernel:
<remote fetch="https://source.codeaurora.org/" name="caf" review="codeaurora.org"/> <default remote="caf" revision="LU.UM.1.2.1.r1.3"/> <project groups="cyborg" name="kernel/msm-4.19" path="src/kernel/msm-4.19" revision="a103f94094dc38bc5931ca8559754e99558c0326" upstream="LU.UM.1.2.1.r1.3"/>
This is the public Qualcomm release of their 4.19 kernel
And the device tree that they use are located under:
src/kernel/msm-4.19/arch/arm64/boot/dts/vendor/qcom/qrb5165-iot-openq.dts
And this is a proprietary device tree, written by Lantronix.
I think Sightline has ordered a device kit, which should be delivered to me at some point. After I get it, I should be able to use its serial ID to get access to documentation and schematics of the board. Then we can port Linux kernel to their SoM/device kit. If you can provide SoM and base board schematics beforehand, it would speed up porting. Another option would be sharing the respective dts files to give us at least some kind of information regarding the board.
So I wouldn't be able to copy the needed files over and replace the device tree that is appeneded currently to the linaro kernel with the one from the Lantronix BSP? Our hope is to possibly get the linaro kernel running on the Lantronix board. If we want to do that, what would be some steps that we could take? We also purchased the Thundercomm platform so I can at least get that up and running but it'd be good to know why the Lantronix device tree wouldn't work with the kernel that is mentioned on the 96boards website.
Thundercomm RB5 device is supported out of the box by the upstream kernel, see the qrb5165-rb5.dts file. Also you might be interested in the qrb5165-rb5-vision-mezzanine.dts which provides additional support for the cameras found on the Vision/Navigation mezzanine (included in the default RB5 kit). The former dts is available since 5.10, receiving incremental updates as the time goes. The later dts was merged into Linux 6.2.
Unfortunately, you can not use device trees from Qualcomm releases with the upstream Linux kernel. Qualcomm writes them in a way that is not acceptable for the upstream kernels. Thus usually we have to repeat the porting up to some point. Basic steps to port Linux to the new Qualcomm-based board are the following: - Identify used PMICs. - Create the empty device tree including SoC and PMIC dtsi files. - Identify used UART and regulator tree. At this point the kernel should be bootable using debugging initramfs image. - Fill in the regulators description in the board dts - Identify storage options (eMMC, UFS, etc). - Identify used bus instances (I2C, SPI, corresponding QUPv3 wrappers, PCIe, USB) - Enable corresponding device nodes. Fill necessary supplies. Write corresponding pinctrl states. - Add support for the rest of necessary onboard devices, which can include sound codes, camera sensors, panel, DSI bridges/panels, etc. This might require writing additional drivers if the particular hardware piece is not supported.
Thanks again!
Patrick Whewell | Software Engineer | SightLine Applications, Inc | Onboard Video Processing
-----Original Message----- From: Dmitry Baryshkov dmitry.baryshkov@linaro.org Sent: Wednesday, March 15, 2023 2:40 AM To: Patrick Whewell patrick.whewell@sightlineapplications.com Subject: Re: Linaro kernel for QRB5165
Hi Patrick
On 14/03/2023 21:24, Patrick Whewell wrote:
Hi Dmitry,
I work over at Sightline Applications and I am working on the Lantronix SOM of the qrb5165. We had a meeting at the beginning of the month to talk about some additional help (on top of the snapdragon 820c work) regarding this kernel and it was mentioned that you were pretty familiar with the qrb5165.
I recently was able to find out the device tree that Lantronix is using in their kernel and my hope was to copy over the files needed to the Linaro repo, build, and hopefully use fastboot boot to test it out.
My question is that I notice the Linaro Kernel is building and then appending two separate .dtb files to the end of the kernel. I have previously worked on systems with u-boot where you select the fdt_file in the u-boot environment. How does this kernel/chip determine which device tree blob to use. I was thinking that it would just pick the first one appended but then it would be pointless to attach two separate blobs in that case.
Yes, unfortunately Qualcomm adopted to use Android boot images and their own proprietary bootloader rather than using one of the standard ones.
The bootloader looks for the 'best match' while looking for the DTB. To accomplish this, it uses DTB's qcom,msm-id, qcom-board-id and qcom,pmic-id to compute the dts 'score', then it uses the DTS with the best score. For example this allows Android team to bundle a single image with DTBs for both RB3 and RB5 boards, with the correct DTB being selected at runtime.
In theory this should also allow you to use a single image for APQ8096 and QR5165 boards. However for the bringup I suggest ignoring that possibility and always using just a single DTB, suitable for your board.
Note: I do not yet have access to Lantronix BSP. If it provides the vendor kernel (and thus vendor DTS), these files are not going to be compatible with the upstream kernel.
Thanks!
*Patrick Whewell*
*Software Engineer*
He/him
_patrick.whewell@sightlineapplications.com mailto:patrick.whewell@sightlineapplications.com_
www.sightlineapplications.com http://www.sightlineapplications.com/
/5711 S Hood Ave., Suite 100/
/Portland, OR 97239/
-- With best wishes Dmitry
-- With best wishes Dmitry