linux-kernel - Re: [PATCH 1/2] dt-bindings: arm,scmi: Do not use clocks for SCMI performance domains

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Message-ID: <CAL_JsqKH9pN7E7o+UY7YmOrOKCUigrMTxY3f3AH4PdpQUAaawg@mail.gmail.com>
Date:   Wed, 21 Oct 2020 11:20:27 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH 1/2] dt-bindings: arm,scmi: Do not use clocks for SCMI
 performance domains

On Tue, Oct 20, 2020 at 3:37 PM Sudeep Holla <sudeep.holla@....com> wrote:
>
> Commit dd461cd9183f ("opp: Allow dev_pm_opp_get_opp_table() to return
> -EPROBE_DEFER") handles -EPROBE_DEFER for the clock/interconnects within
> _allocate_opp_table() which is called from dev_pm_opp_add and it
> now propagates the error back to the caller.
>
> SCMI performance domain re-used clock bindings to keep it simple. However
> with the above mentioned change, if clock property is present in a device
> node, opps can't be added until clk_get succeeds. So in order to fix the
> issue, we can register dummy clocks which is completely ugly.
>
> Since there are no upstream users for the SCMI performance domain clock
> bindings, let us introduce separate performance domain bindings for the
> same.
>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  .../devicetree/bindings/arm/arm,scmi.txt      | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
>
> Hi Rob/Viresh,
>
> This is actually a fix for the regression I reported here[1].
> I am not adding fixes tag as I am targeting in the same release and
> also because it is not directly related.
>
> Regards,
> Sudeep
>
> [1] https://lore.kernel.org/r/20201015180555.gacdzkofpibkdn2e@bogus
>
> P.S.:/me records that this binding needs to be moved to yaml in v5.11
>
> diff --git a/Documentation/devicetree/bindings/arm/arm,scmi.txt b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> index 55deb68230eb..0a6c1b495403 100644
> --- a/Documentation/devicetree/bindings/arm/arm,scmi.txt
> +++ b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> @@ -44,7 +44,7 @@ as described in the following sections. If the platform supports dedicated
>  mboxes, mbox-names and shmem shall be present in the sub-node corresponding
>  to that protocol.
>
> -Clock/Performance bindings for the clocks/OPPs based on SCMI Message Protocol
> +Clock bindings for the clocks based on SCMI Message Protocol
>  ------------------------------------------------------------
>
>  This binding uses the common clock binding[1].
> @@ -52,6 +52,19 @@ This binding uses the common clock binding[1].
>  Required properties:
>  - #clock-cells : Should be 1. Contains the Clock ID value used by SCMI commands.
>
> +Performance bindings for the OPPs based on SCMI Message Protocol
> +------------------------------------------------------------
> +
> +Required properties:
> +- #perf-domain-cells: Should be 1. Contains the performance domain ID value
> +                     used by SCMI commands.

When is this not 1 (IOW, you only need this if variable)? How would it
be used outside SCMI (given it has a generic name)?

> +
> +* Property arm,scmi-perf-domain

Yet this doesn't have a generic name. You mentioned on IRC this is
aligned with QCom, but why can't QCom use the same property here?

Really though, why can't you give SCMI a CPUs MPIDR and get its domain?

Rob