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Subject: Re: [PATCH v2 11/11] interconnect: Add devfreq support
To:     Saravana Kannan <saravanak@google.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
        Stephen Boyd <sboyd@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>
Cc:     Rajendra Nayak <rnayak@codeaurora.org>,
        Jordan Crouse <jcrouse@codeaurora.org>,
        vincent.guittot@linaro.org, bjorn.andersson@linaro.org,
        amit.kucheria@linaro.org, seansw@qti.qualcomm.com,
        daidavid1@codeaurora.org, evgreen@chromium.org,
        sibis@codeaurora.org, kernel-team@android.com,
        linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20190614041733.120807-1-saravanak@google.com>
 <20190614041733.120807-12-saravanak@google.com>
From:   Georgi Djakov <georgi.djakov@linaro.org>
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Message-ID: <5dc6c820-ead8-d0dc-44de-4d13f86df042@linaro.org>
Date:   Mon, 17 Jun 2019 18:43:53 +0300
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In-Reply-To: <20190614041733.120807-12-saravanak@google.com>
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Hi Saravana,

On 6/14/19 07:17, Saravana Kannan wrote:
> Add a icc_create_devfreq() and icc_remove_devfreq() to create and remove
> devfreq devices for interconnect paths. A driver can create/remove devfreq
> devices for the interconnects needed for its device by calling these APIs.
> This would allow various devfreq governors to work with interconnect paths
> and the device driver itself doesn't have to actively manage the bandwidth
> votes for the interconnects.

Thanks for the patches, but creating devfreq devices for each interconnect path
seems odd to me - at least for consumers that already use a governor. So for DDR
scaling for example, are you suggesting that we add a devfreq device from the
cpufreq driver in order to scale the interconnect between CPU<->DDR? Also if the
GPU is already using devfreq, should we add a devfreq per each interconnect
path? What would be the benefit in this case - using different governors for
bandwidth scaling maybe?

Thanks,
Georgi