Re: [PATCH v2 1/8] arm64: dts: db820c: add basic board support

From: Srinivas Kandagatla
Date: Wed Jun 22 2016 - 04:52:24 EST




On 22/06/16 05:49, Bjorn Andersson wrote:
On Tue 21 Jun 10:22 PDT 2016, Srinivas Kandagatla wrote:

[..]
diff --git a/arch/arm64/boot/dts/qcom/apq8096-db820c.dts b/arch/arm64/boot/dts/qcom/apq8096-db820c.dts
[..]
+
+/ {
+ model = "Qualcomm Technologies, Inc. DB820c";
+ compatible = "qcom,apq8096-sbc";

I'm still not buying the concept of this being the one and only
single-board-computer.

+1

AFAIK, The problem is the dtbTool. dtbTool has predefined all the platform names along with its platform ID's [1] for auto generating board-id, pmic-id and soc-id. dtbTool checks the compatible strings along with soc name with its static list, it would fail if it did not find a matching combination of soc,platform compatible.

Either we have to cope up with this and have a compatbile strings which keep dtbTool happy
or
Keep patching dtbtool to be more flexible.

There is another problem with dtbTool, We can not use dtbTool with new boards from other vendors with own board names, like SD600 or IFC6410 and so..


IMO, we should patch dtbTool to make it more flexible to cope up with situations like this.

If this compatible fully and exclusively identifies this particular
board then dtbTool should be updated to follow the product name
"qcom,apq8096-db820c". If on the other hand this identifies a class of
single-board-computers, then the compatible should list both
"qcom,apq8096-dtb820c" and "qcom,apq8096-sbc".

Am not sure this would actually work when we have two boards with same sbc platform ID. Which one would the bootloader pick? and on what basis?




Further more, the ePAPR defines this property as:
"Specifies a list of platform architectures with which this platform is
compatible. This property can be used by operating systems in selecting
platform specific code."

So I think we should follow the common pattern of having the least
significant entry being "qcom,apq8096".
I agree.

Thanks,
srini

[1] https://source.codeaurora.org/quic/kernel/skales/tree/dtbTool#n83




+};

Regards,
Bjorn