Re: [RFC PATCH 2/2] arm64: dts: qcom: qcm6490: Add qcm6490 idp and rb3 board

[Mukesh Ojha <quic_mojha@quicinc.com>]

On 11/6/2023 5:24 PM, Dmitry Baryshkov wrote:
> On Mon, 6 Nov 2023 at 13:41, Mukesh Ojha <quic_mojha@quicinc.com> wrote:
>>
>>
>> On 11/5/2023 6:38 PM, Krzysztof Kozlowski wrote:
>>> On 03/11/2023 23:22, Dmitry Baryshkov wrote:
>>>> On Fri, 3 Nov 2023 at 20:49, Komal Bajaj <quic_kbajaj@quicinc.com> wrote:
>>>>>
>>>>> Add qcm6490 devicetree file for QCM6490 IDP and QCM6490 RB3
>>>>> platform. QCM6490 is derived from SC7280 meant for various
>>>>> form factor including IoT.
>>>>>
>>>>> Supported features are, as of now:
>>>>> * Debug UART
>>>>> * eMMC (only in IDP)
>>>>> * USB
>>>>>
>>>
>>> ...
>>>
>>>>> +
>>>>> diff --git a/arch/arm64/boot/dts/qcom/qcm6490-iot-common.dtsi b/arch/arm64/boot/dts/qcom/qcm6490-iot-common.dtsi
>>>>> new file mode 100644
>>>>> index 000000000000..01adc97789d0
>>>>> --- /dev/null
>>>>> +++ b/arch/arm64/boot/dts/qcom/qcm6490-iot-common.dtsi
>>>>
>>>> I have mixed feelings towards this file. Usually we add such 'common'
>>>> files only for the phone platforms where most of the devices are
>>>> common.
>>>> Do you expect that IDP and RB3 will have a lot of common code other
>>>> than these regulator settings?
>>>
>>> I agree here. What exactly is common in the real hardware between IDP
>>> and RB3? Commit msg does not explain it, so I do not see enough
>>> justification for common file. Just because some DTS looks similar for
>>> different hardware does not mean you should creat common file.
>>
>> @Dmitry/@Krzysztof,
>>
>> Thank you for reviewing the RFC, we wanted to continue the
>> suggestion/discussion given on [1] , where we discussed that this
>> qcm6490 is going to be targeted for IOT segment and will have different
>> memory map and it is going to use some of co-processors like adsp/cdsp
>> which chrome does not use.
>>
>> So to your question what is common between RB3 and IDP, mostly they will
>> share common memory map(similar to [2]) and regulator settings and both
>> will use adsp/cdsp etc., we will be posting the memory map changes as
>> well in coming weeks once this RFC is acked.
> 
> Is the memory map going to be the same as the one used on Fairphone5?

No, Fairphone5 looks to be using chrome memory map and i suggested
here to move them into sc7280.dtsi

https://lore.kernel.org/lkml/d5d53346-ca3b-986a-e104-d87c37115b62@quicinc.com/

> 
> Are ADSP and CDSP physically present on sc7280?

Yes, they are present but not used.

> 
> I think that your goal should be to:
> - populate missing device in sc7280.dtsi
> - maybe add qcm6490.dtsi which defines SoC-level common data (e.g. memory map)
> - push the rest to board files.

Agree to all of the point.
We started with the same thought at[3] but it got lost in discussion
due to its differentiation with mobile counter part(fairphone) which
follow chrome memory map and hence we came up with qcm6490-iot-common.
Do you think, qcm6490-iot.dtsi should be good ?

[3]
https://lore.kernel.org/linux-arm-msm/20231003175456.14774-3-quic_kbajaj@quicinc.com/

-Mukesh
> 
> I don't think that putting regulators to the common file is a good
> idea. Platforms will further change and limit voltage limits and
> modes, so they usually go to the board file.
> 
>>
>>
>> Thanks,
>> Mukesh
>>
>> [1]
>> https://lore.kernel.org/linux-arm-msm/d97ebf74-ad03-86d6-b826-b57be209b9e2@quicinc.com/
>>
>> [2]
>> commit 90c856602e0346ce9ff234062e86a198d71fa723
>> Author: Douglas Anderson <dianders@chromium.org>
>> Date:   Tue Jan 25 14:44:20 2022 -0800
>>
>>       arm64: dts: qcom: sc7280: Factor out Chrome common fragment
>>
>>       This factors out a device tree fragment from some sc7280 device
>>       trees. It represents the device tree bits that should be included for
>>       "Chrome" based sc7280 boards. On these boards the bootloader (Coreboot
>>       + Depthcharge) configures things slightly different than the
>>       bootloader that Qualcomm provides. The modem firmware on these boards
>>       also works differently than on other Qulacomm products and thus the
>>       reserved memory map needs to be adjusted.
>>
>>       NOTES:
>>       - This is _not_ quite a no-op change. The "herobrine" and "idp"
>>         fragments here were different and it looks like someone simply
>>         forgot to update the herobrine version. This updates a few numbers
>>         to match IDP. This will also cause the `pmk8350_pon` to be disabled
>>         on idp/crd, which I belive is a correct change.
>>       - At the moment this assumes LTE skus. Once it's clearer how WiFi SKUs
>>         will work (how much of the memory map they can reclaim) we may add
>>         an extra fragment that will rejigger one way or the other.
>>
>>       Signed-off-by: Douglas Anderson <dianders@chromium.org>
>>       Reviewed-by: Stephen Boyd <swboyd@chromium.org>
>>       Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
>>       Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
>>       Link:
>> https://lore.kernel.org/r/20220125144316.v2.3.Iac012fa8d727be46448d47027a1813ea716423ce@changeid
>>
>>
>>>
>>> Best regards,
>>> Krzysztof
>>>
> 
> 
>