linux-kernel - Re: [RFC PATCH 0/3] Add support of busfreq

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Date:   Fri, 3 May 2019 13:19:08 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Alexandre Bailon <abailon@...libre.com>
Cc:     linux-pm@...r.kernel.org, georgi.djakov@...aro.org,
        mturquette@...libre.com, ptitiano@...libre.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        zening.wang@....com, aisheng.dong@....com, khilman@...libre.com,
        ccaione@...libre.com, Viresh Kumar <viresh.kumar@...aro.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
Subject: Re: [RFC PATCH 0/3] Add support of busfreq

On Wed, 13 Mar 2019 at 20:35, Alexandre Bailon <abailon@...libre.com> wrote:
>
> This series implements busfreq, a framework used in MXP's
> tree to scale the interconnect and dram frequencies.
> In the vendor tree, device's driver request for a
> performance level, which is used to scale the frequencies.
> This series implements it using the interconnect framework.
> Devices' driver request for bandwidth which is use by busfreq
> to determine a performance level, and then scale the frequency.
>
> Busfreq is quite generic. It could be used for any i.MX SoC.
> A busfreq platform driver just have to define a list of
> interconnect nodes, and some OPPs.
>
> This series is sent as RFC mostly because the current support
> of i.MX SoC won't benefit of busfreq framework, because the
> clocks' driver don't support interconnect / dram frequency
> scaling.
> As exemple, this series implements busfreq for i.MX8MM whose
> upstreaming is in progress. Because this relies on ATF to
> do the frequency scaling, it won't be hard make it work.
>
> As exemple, this series implements busfreq for
> Alexandre Bailon (3):
>   drivers: interconnect: Add a driver for i.MX SoC
>   drivers: interconnect: imx: Add support of i.MX8MM
>   dt-bindings: interconnect: Document fsl,busfreq-imx8mm bindings

Hi Alexandre,

I am quite late but I just found your email.

This looks very similar to existing framework - devfreq, which purpose
is to scale the system busses based on performance counters/events. It
would be nice if we could avoid duplication of existing subsystems.

Best regards,
Krzysztof