linux-kernel - Re: [PATCH v7 2/6] interconnect: Add generic interconnect driver for Exynos SoCs

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Message-ID: <9081148f-5ed4-97a3-84a9-4ea3eb157b73@samsung.com>
Date:   Tue, 3 Nov 2020 18:30:40 +0100
From:   Sylwester Nawrocki <s.nawrocki@...sung.com>
To:     cwchoi00@...il.com
Cc:     Chanwoo Choi <cw00.choi@...sung.com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Artur Świgoń <a.swigon@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v7 2/6] interconnect: Add generic interconnect driver
 for Exynos SoCs

On 03.11.2020 15:12, Chanwoo Choi wrote:
>>> I have a question about exynos_icc_get_parent().
>>> As I checked, this function returns the only one icc_node
>>> as parent node. But, bus_display dt node in the exynos4412.dtsi
>>> specifies the two interconnect node as following with bus_leftbus, bus_dmc,
>>>
>>> When I checked the return value of exynos_icc_get_parent()
>>> during probing for bus_display device, exynos_icc_get_parent() function
>>> only returns 'bus_leftbus' icc_node. Do you need to add two phandle
>>> of icc node?
>> Yes, as we use the interconnect consumer bindings we need to specify a path,
>> i.e. a <initiator, target> pair. When the provider node initializes it will
>> link itself to that path. Currently the provider driver uses just the first
>> phandle.

> As I knew, the interconnect consumer bindings use the two phandles
> in the interconnect core as you commented. But, in case of this,
> even if add two phandles with interconnect consuming binding style,
> the exynos interconnect driver only uses the first phandle.
> 
> Instead, I think we better explain this case into a dt-binding
> document for users.

Fair enough, I'll try to improve the description, do you perhaps have 
any suggestions?

The DT binding reflects how the hardware structure looks like and the
fact that the driver currently uses only one of the phandles could be
considered an implementation detail.

-- 
Regards,
Sylwester