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Fri, 27 Dec 2019 09:03:09 +0900 (KST) Received: from [10.113.221.102] (unknown [10.113.221.102]) by epsmtip2.samsung.com (KnoxPortal) with ESMTPA id 20191227000308epsmtip2d2aa064d3f8397a927215c21eb2df2a5~kEXraFDV_2373323733epsmtip2Y; Fri, 27 Dec 2019 00:03:08 +0000 (GMT) Subject: Re: [PATCH 4/9] PM / devfreq: exynos-bus: Replace deprecated 'devfreq' property To: Rob Herring Cc: krzk@kernel.org, mark.rutland@arm.com, heiko@sntech.de, leonard.crestez@nxp.com, lukasz.luba@arm.com, a.swigon@samsung.com, m.szyprowski@samsung.com, kgene@kernel.org, myungjoo.ham@samsung.com, kyungmin.park@samsung.com, linux-pm@vger.kernel.org, linux-samsung-soc@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org From: Chanwoo Choi Organization: Samsung Electronics Message-ID: Date: Fri, 27 Dec 2019 09:09:58 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:59.0) Gecko/20100101 Thunderbird/59.0 MIME-Version: 1.0 In-Reply-To: <20191226210119.GA8706@bogus> Content-Language: en-US Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrAJsWRmVeSWpSXmKPExsWy7bCmrq6tF2ucQcMSG4v781oZLeYfOcdq 8f/Ra1aL/sevmS3On9/AbnG26Q27xYq7H1ktNj2+xmpxedccNovPvUcYLT49+M9sMeP8PiaL hU0t7BZrj9xlt1h6/SKTxe3GFWwW//fsYHcQ9Fgzbw2jx6ZVnWwem5fUe2x8t4PJo2/LKkaP 7dfmMXt83iQXwB6VbZORmpiSWqSQmpecn5KZl26r5B0c7xxvamZgqGtoaWGupJCXmJtqq+Ti E6DrlpkD9IGSQlliTilQKCCxuFhJ386mKL+0JFUhI7+4xFYptSAlp8CyQK84Mbe4NC9dLzk/ 18rQwMDIFKgwITvj8fMXbAV/RSpWH/3B0sA4XbCLkZNDQsBEYuP9Y+wgtpDADkaJ0x99uhi5 gOxPjBI7Vr9hhXC+MUrMOPIPyOEA6/i0yREivpdR4tXM34wQzntGidkfG9lARgkLRElsO7CI FcQWEVCU+N02DWwSs8AaZom2Kb9ZQBJsAloS+1/cAGvgByq6+uMxI4jNK2An8fbsBGYQm0VA VeLIkWdg9aICYRInt7VA1QhKnJz5BCzOCTTnxcqPYMuYBcQlbj2ZzwRhy0tsfzuHGWSxhMAx dokzE5uZIJ52kZh6+SiULSzx6vgWdghbSuJlfxuUXS2x8uQRNojmDkaJLfsvsEIkjCX2L53M BAoLZgFNifW79CHCihI7f89lhFjMJ/Huaw80uHglOtqEIEqUJS4/uAu1VlJicXsn2wRGpVlI 3pmF5IVZSF6YhbBsASPLKkax1ILi3PTUYsMCY+TY3sQITt1a5jsYN5zzOcQowMGoxMPbsYsl Tog1say4MvcQowQHs5II7+oixjgh3pTEyqrUovz4otKc1OJDjKbA0J7ILCWanA/MK3kl8Yam RsbGxhYmhmamhoZK4rwcPy7GCgmkJ5akZqemFqQWwfQxcXBKNTB26X883hietu9N98/8E4fc wqRVJ0coJCxLXtK6eLrp24KzflmPPZM/X4xSm3NQ6In2al/Bkm+7835WSdQWfeCcsGrKnM+e 018y5PR0ZcXsd9ISuPbeg0PjEot6xNH6pMKEK7vbYwtkuf68+7lb7f/Ch9tetLiVz2e1XGgw sf+qnOPRRQvuXjVUYinOSDTUYi4qTgQAq4eALvMDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrFIsWRmVeSWpSXmKPExsWy7bCSvK6tF2ucwdIgi/vzWhkt5h85x2rx /9FrVov+x6+ZLc6f38BucbbpDbvFirsfWS02Pb7GanF51xw2i8+9RxgtPj34z2wx4/w+JouF TS3sFmuP3GW3WHr9IpPF7cYVbBb/9+xgdxD0WDNvDaPHplWdbB6bl9R7bHy3g8mjb8sqRo/t 1+Yxe3zeJBfAHsVlk5Kak1mWWqRvl8CV8fj5C7aCvyIVq4/+YGlgnC7YxcjBISFgIvFpk2MX IxeHkMBuRomdFxezdTFyAsUlJaZdPMoMUSMscfhwMUTNW0aJ7R8fgtUIC0RJbDuwiBXEFhFQ lPjdNo0VpIhZYA2zxPmebhaIjruMEvt2NTGCVLEJaEnsf3EDrJsfqOPqj8dgcV4BO4m3Zycw g9gsAqoSR448YwGxRQXCJHYuecwEUSMocXLmE7A4J9CcFys/gm1mFlCX+DPvEjOELS5x68l8 JghbXmL72znMExiFZyFpn4WkZRaSlllIWhYwsqxilEwtKM5Nzy02LDDMSy3XK07MLS7NS9dL zs/dxAiOYS3NHYyXl8QfYhTgYFTi4e3YxRInxJpYVlyZe4hRgoNZSYR3dRFjnBBvSmJlVWpR fnxRaU5q8SFGaQ4WJXHep3nHIoUE0hNLUrNTUwtSi2CyTBycUg2MTirzBWe0Xu0+nLptsdTs Qm2R/PmtLFvbtWQeWgp3hQZnGHKcWx+yj8X37o9JHbd0twWIsTetFbt/fJnz7L8WQYyWfsaL RA3a0nL8Zpzl704O/TFRYrqBQvF82fBN/bOfH5XkY9ko5yYcVLpn0wuF/Wb99YqVYWEfXaRC /at45d7G3vqp8FeJpTgj0VCLuag4EQA70uBv3QIAAA== X-CMS-MailID: 20191227000309epcas1p145ab877d7254a2e5e29c1a33b02dd583 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20191217055106epcas1p11f2bc81d6bb2db3fc4bc257d78c337b9 References: <20191217055738.28445-1-cw00.choi@samsung.com> <20191217055738.28445-5-cw00.choi@samsung.com> <20191226210119.GA8706@bogus> Sender: linux-samsung-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org On 12/27/19 6:01 AM, Rob Herring wrote: > On Tue, Dec 17, 2019 at 02:57:33PM +0900, Chanwoo Choi wrote: >> In order to remove the deprecated 'devfreq' property, replace with >> new 'exynos,parent-bus' property in order to get the parent devfreq device >> in devicetree file instead of 'devfreq' property. But, to guarantee the >> backward-compatibility, keep the support 'devfreq' property. >> >> Signed-off-by: Chanwoo Choi >> --- >> .../bindings/devfreq/exynos-bus.txt | 16 +++++++-------- >> drivers/devfreq/exynos-bus.c | 20 ++++++++++++------- >> 2 files changed, 21 insertions(+), 15 deletions(-) >> >> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> index e71f752cc18f..c948cee01124 100644 >> --- a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> @@ -45,7 +45,7 @@ Required properties only for parent bus device: >> of buses. >> >> Required properties only for passive bus device: >> -- devfreq: the parent bus device. >> +- exynos,parent-bus: the parent bus device. > > If you are going to do something new, why not use the interconnect > binding here? As I knew, interconnect make the data path among multiple nodes and set the average and peak bandwidth to the specific data path. It means that some data will be flowed from node_a to node_d or the reverse way because each node has the tightly coupled dependency for data flow. node_a <-> node_b <-> node_c <-> node_d On the other hand, exynos-bus.c driver is not related to 'data path'. Each bus just need to control the their own frequency and voltage. But, share the power line (regulator) between exynos-bus device even if there are no any dependency of data flow. 'exynos,parent-bus' property just indicate the specific devfreq device(parent bus device) which controls the shared power line(regulator) in order to prevent the h/w problem due to the wrong pair of frequency and voltage. 'exynos,parent-bus' property is only used to catch the change timing of shared power line. And, as you commented, there are some data path among the exynos-bus devices for the display h/w as following: bus_display -> bus_leftbus -> bus_dmc In order to make the data path between bus devices, interconnect binding is required. This approach[1] was posted. [1] https://patchwork.kernel.org/cover/11305265/ - [RFC,v3,0/7] PM / devfreq: Simple QoS for exynos-bus using interconnect -- Best Regards, Chanwoo Choi Samsung Electronics