linux-kernel - Re: [PATCH v6 6/7] dt: thermal: tsens: Document the fallback DT property for v2 of TSENS IP

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Message-ID: <CAD=FV=W-snhM9L9Ez-ypAJwn2NhNJ1X=s5wDvu-gbQvmLZY9Qg@mail.gmail.com>
Date:   Wed, 11 Jul 2018 11:42:19 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Amit Kucheria <amit.kucheria@...aro.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Eduardo Valentin <edubezval@...il.com>,
        smohanad@...eaurora.org,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Andy Gross <andy.gross@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v6 6/7] dt: thermal: tsens: Document the fallback DT
 property for v2 of TSENS IP

Hi,

On Mon, Jul 9, 2018 at 4:43 AM, Amit Kucheria <amit.kucheria@...aro.org> wrote:
> We want to create common code for v2 of the TSENS IP block that is used in
> a large number of Qualcomm SoCs. "qcom,tsens-v2" should be able to handle
> most of the common functionality start with a common get_temp() function.
>
> It is also necessary to split out the memory regions for the TM and SROT
> register banks because their offsets are not constant across SoC families.

nit that bindings should be earlier in the patch series than the code
implementing the bindings.


> Signed-off-by: Amit Kucheria <amit.kucheria@...aro.org>
> ---
>  .../devicetree/bindings/thermal/qcom-tsens.txt     | 25 +++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/thermal/qcom-tsens.txt b/Documentation/devicetree/bindings/thermal/qcom-tsens.txt
> index 06195e8..8f963b1 100644
> --- a/Documentation/devicetree/bindings/thermal/qcom-tsens.txt
> +++ b/Documentation/devicetree/bindings/thermal/qcom-tsens.txt
> @@ -1,10 +1,16 @@
>  * QCOM SoC Temperature Sensor (TSENS)
>
>  Required properties:
> -- compatible :
> - - "qcom,msm8916-tsens" : For 8916 Family of SoCs
> - - "qcom,msm8974-tsens" : For 8974 Family of SoCs
> - - "qcom,msm8996-tsens" : For 8996 Family of SoCs
> +- compatible:
> +  Must be one of the following:
> +    - "qcom,msm8916-tsens" (MSM8916)
> +    - "qcom,msm8974-tsens" (MSM8974)
> +    - "qcom,msm8996-tsens" (MSM8996)
> +    - "qcom,msm8998-tsens", "qcom,tsens-v2" (MSM8998)
> +    - "qcom,sdm845-tsens", "qcom,tsens-v2" (SDM845)
> +  The generic "qcom,tsens-v2" property must be used as a fallback for any SoC with
> +  version 2 of the TSENS IP. MSM8996 is the only exception beacause the generic
> +  property did not exist when support was added.
>
>  - reg: Address range of the thermal registers

You need to document that for old SoCs where TM / SROT were 0x1000
apart (SROT first) that one "reg" field was OK.  ...and that for new
SoCs you specify two reg ranges: the first for TM and the second for
SROT.


>  - #thermal-sensor-cells : Should be 1. See ./thermal.txt for a description.
> @@ -12,7 +18,7 @@ Required properties:
>  - Refer to Documentation/devicetree/bindings/nvmem/nvmem.txt to know how to specify
>  nvmem cells
>
> -Example:
> +Example 1 (legacy support before a fallback tsens-v2 propoerty was introduced):
>  tsens: thermal-sensor@...000 {
>                 compatible = "qcom,msm8916-tsens";
>                 reg = <0x4a8000 0x2000>;
> @@ -20,3 +26,12 @@ tsens: thermal-sensor@...000 {
>                 nvmem-cell-names = "caldata", "calsel";
>                 #thermal-sensor-cells = <1>;
>         };
> +
> +Example 2 (for any platform containing v2 of the TSENS IP):
> +tsens0: tsens@...2000 {

A) Use a generic name for the node, not a specific one.  Thus the node
should be "thermal-sensor", not "tsens".

B) This unit address needs to match the _first_ reg address listed.
Give your reg below, this should be @c263000

Thus your node name should be:

tsens0: thermal-sensor@...3000 {

> +               compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
> +               reg = <0xc263000 0x1ff>, /* TM */
> +                       <0xc222000 0x1ff>; /* SROT */
> +               #qcom,sensors = <13>;

The "#qcom,sensors" property seems wrong in a few ways:

A) I wouldn't have expected it to start with a "#".  I only expect to
see that on things specifying sizes / lengths.  Rob can feel free to
override me, though.

B) It's not documented above.  Just putting something in an example
doesn't document it--it needs to be listed in the "Optional
properties".