linux-kernel - Re: [PATCH v2 3/3] arm64: dts: sdm845: Add serial console support

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Date:   Wed, 7 Feb 2018 09:58:58 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        devicetree@...r.kernel.org, Stephen Boyd <sboyd@...eaurora.org>,
        evgreen@...omium.org
Subject: Re: [PATCH v2 3/3] arm64: dts: sdm845: Add serial console support

[]..

>> @@ -10,4 +10,46 @@
>>  / {
>>         model = "Qualcomm Technologies, Inc. SDM845 MTP";
>>         compatible = "qcom,sdm845-mtp";
>> +
>> +       aliases {
>> +               serial0 = &qup_uart2;
>> +       };
>> +
>> +       chosen {
>> +               stdout-path = "serial0";
>> +       };
>> +
>> +       soc {
> 
> I don't know if there's an official position, but in general I'm seen
> people use the actual "soc" alias here.  AKA at the top level of this
> dts, just do:
> 
> &soc {
>   ...
> };
> 
> Normally doing stuff like that is useful so you don't need to
> replicate the whole hierarchy.  In this case that's not a huge
> savings, but it can be nice to be consistent.  In the very least it
> saves you a level of indentation.
> 
> 
>> +               serial@...000 {
>> +                       status = "okay";
>> +               };
> 
> Similarly here you can use the alias from the sdm845.dtsi file to
> avoid replicating the hierarchy.  AKA at the top level do:
> 
> &qup_uart2 {
>   status = "okay";
> };
> 
> In this case it saves you 2 levels of indentation.

Right. Andy/Bjorn, are there any preferences here?
I see we don't do this for the other board files, and I not sure
theres a specific reasoning for how its currently done and if we
need to stick to it.

> 
>> +
>> +               pinctrl@...0000 {
>> +                       qup_uart2_default: qup_uart2_default {
> 
> I'm not sure how persnickety I should be, but according to
> <https://elinux.org/Device_Tree_Linux>:
> 
>   node names use dash "-" instead of underscore "_"
> 
> ...but, of course, labels can't use dashes (and the same page says to
> use underscore for labels).  This is why, in rk3288 for instance, you
> see:
> 
> i2c2_xfer: i2c2-xfer {
>   rockchip,pins = <6 9 RK_FUNC_1 &pcfg_pull_none>,
>   <6 10 RK_FUNC_1 &pcfg_pull_none>;
> };
> 
> AKA the label and the node name are the same but the label uses "_"
> and the node names use "-".

Sure, I'll fix these up.

[]
>> diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
>> index 02520f19e4ca..c4ce70840acf 100644
>> --- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
>> +++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
>> @@ -4,6 +4,7 @@
>>   */
>>
>>  #include <dt-bindings/interrupt-controller/arm-gic.h>
>> +#include <dt-bindings/clock/qcom,gcc-sdm845.h>
>>
>>  / {
>>         model = "Qualcomm Technologies, Inc. SDM845";
>> @@ -273,5 +274,25 @@
>>                         cell-index = <0>;
>>                 };
>>
>> +               qup_1: qcom,geni_se@...000 {
>> +                       compatible = "qcom,geni-se-qup";
>> +                       reg = <0xac0000 0x6000>;
> 
> I think you may have mentioned this in another context, but this
> doesn't match the current bindings.  Some clocks should be here.
> ...and it looks like the uart should be a subnode.

right, these were tested with the v1 set for serial. I will update them.

regards
Rajendra

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