linux-kernel - Re: [PATCH v3 2/2] PM / devfreq: Add devfreq driver for interconnect bandwidth voting

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Date:   Tue, 7 Aug 2018 10:51:03 -0600
From:   Rob Herring <robh@...nel.org>
To:     Saravana Kannan <skannan@...eaurora.org>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Mark Rutland <mark.rutland@....com>, georgi.djakov@...aro.org,
        vincent.guittot@...aro.org, daidavid1@...eaurora.org,
        bjorn.andersson@...aro.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] PM / devfreq: Add devfreq driver for interconnect
 bandwidth voting

On Wed, Aug 01, 2018 at 05:57:42PM -0700, Saravana Kannan wrote:
> This driver registers itself as a devfreq device that allows devfreq
> governors to make bandwidth votes for an interconnect path. This allows
> applying various policies for different interconnect paths using devfreq
> governors.
> 
> Example uses:
> * Use the devfreq performance governor to set the CPU to DDR interconnect
>   path for maximum performance.
> * Use the devfreq performance governor to set the GPU to DDR interconnect
>   path for maximum performance.
> * Use the CPU frequency to device frequency mapping governor to scale the
>   DDR frequency based on the needs of the CPUs' current frequency.
> 
> Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
> ---
>  Documentation/devicetree/bindings/devfreq/icbw.txt |  21 ++++

Please make bindings separate a patch.

>  drivers/devfreq/Kconfig                            |  13 +++
>  drivers/devfreq/Makefile                           |   1 +
>  drivers/devfreq/devfreq_icbw.c                     | 116 +++++++++++++++++++++
>  4 files changed, 151 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/devfreq/icbw.txt
>  create mode 100644 drivers/devfreq/devfreq_icbw.c
> 
> diff --git a/Documentation/devicetree/bindings/devfreq/icbw.txt b/Documentation/devicetree/bindings/devfreq/icbw.txt
> new file mode 100644
> index 0000000..36cf045
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/devfreq/icbw.txt
> @@ -0,0 +1,21 @@
> +Interconnect bandwidth device
> +
> +icbw is a device that represents an interconnect path that connects two
> +devices. This device is typically used to vote for BW requirements between
> +two devices. Eg: CPU to DDR, GPU to DDR, etc

I'm pretty sure this doesn't represent a h/w device. This usage doesn't 
encourage me to accept the interconnects binding either.

> +
> +Required properties:
> +- compatible:		Must be "devfreq-icbw"
> +- interconnects:	Pairs of phandles and interconnect provider specifier
> +			to denote the edge source and destination ports of
> +			the interconnect path. See also:
> +		Documentation/devicetree/bindings/interconnect/interconnect.txt
> +- interconnect-names:	Must have one entry with the name "path".

That's pretty useless...

> +
> +Example:
> +
> +	qcom,cpubw {

Someone in QCom please broadcast to stop using qcom,foo for node names. 
It is amazing how consistent you all are. If only folks were as 
consistent in reading 
Documentation/devicetree/bindings/submitting-patches.txt.

Rob