linux-kernel - Re: [PATCH 1/7] dt-bindings: soc: qcom: Add qcom-pbs bindings

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Date:   Wed, 12 Jul 2023 17:35:05 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Anjelique Melendez <quic_amelende@...cinc.com>,
        Rob Herring <robh@...nel.org>, pavel@....cz, lee@...nel.org,
        thierry.reding@...il.com, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, agross@...nel.org, andersson@...nel.org,
        konrad.dybcio@...aro.org, u.kleine-koenig@...gutronix.de,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-pwm@...r.kernel.org
Subject: Re: [PATCH 1/7] dt-bindings: soc: qcom: Add qcom-pbs bindings

On Wed, 12 Jul 2023 at 17:22, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 11/07/2023 22:12, Anjelique Melendez wrote:
>
> >>>
> >>> On PMI632, peripherals are partitioned over 2 different SIDs
> >>> (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/pmi632.dtsi?h=v6.5-rc1#n42
> >>> and https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/pmi632.dtsi?h=v6.5-rc1#n149).
> >>> Unfortunately, the pbs peripheral and the lpg peripherals are on different
> >>> PMI632 devices and therefore have different regmaps.
> >>>
> >>> If we get rid of the pbs node we need to get a handle to the proper regmap.
> >>> I see two possible options, we could either introduce a new client property
> >>> which points to a peripheral on the same device as pbs.
> >>>
> >>> i.e.
> >>>     led-controller {
> >>>             compatible = "qcom,pmi632-lpg";
> >>>                     #address-cells = <1>;
> >>>                     #size-cells = <0>;
> >>>                     #pwm-cells = <2>;
> >>>                     nvmem-names = "lpg_chan_sdam";
> >>>                     nvmem = <&pmi632_sdam7>;
> >>>                     qcom,pbs-phandle = <&pmi632_gpios>;
> >>>                     .....
> >>>     };
> >>> Then when client is probing could do something like the following to get the regmap
> >>>
> >>>     dn = of_parse_phandle(node, "qcom,pbs-phandle", 0);
> >>>     pdev = of_find_device_by_node(dn);
> >>>     pbs_regmap = dev_get_regmap(&pdev->dev->parent, NULL);
> >>>
> >>>
> >>>
> >>> Or we could use the nvmem phandle and just have something like this in client's probe
> >>>
> >>>     dn = of_parse_phandle(node, "nvmem", 0);
> >>>     pdev = of_find_device_by_node(dn);
> >>>     pbs_regmap = dev_get_regmap(&pdev->dev->parent, NULL);
> >>>
> >>>
> >>>
> >>> Let me know what your thoughts are on this.
> >>
> >> Rob asked you - "Is there more than 1 instance in a PMIC?" - and you did
> >> not answer positively, just mentioned something about drivers in
> >> downstream, which do not matter. So is the answer for that question:
> >> yes, you have two instances of the same PMIC differing by presence of
> >> PBS and other features"?
> >>
> > Sorry that was a misunderstanding on my part.
> > Yes, answer to Rob's question should have been "We have two instances of PMI632,
> > where one instance holds the pbs peripheral and the other holds the lpg
> > peripherals. The child node for pbs is needed so lpg client can access
> > the PMI632 regmap which contains the pbs peripheral."
>
> I guess I miss here something. What is "LPG client"? I don't understand
> why this LPG client needs existence of PBS node, to be able to get the
> regmap.
>
> PBS is a child of PMIC, so it can get regmap from the parent. What's
> more, which DT property passes the regmap from PMIC to LPG client?

There are some PMICs which claim two SPMI SIDs. For such PMICs, each
SID is a separate device, so it is not directly possible to get the
regmap of the other SID.

-- 
With best wishes
Dmitry