From: Chanwoo Choi <cw00.choi@samsung.com>
To: Rob Herring <robh@kernel.org>
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
Subject: Re: [PATCH 4/9] PM / devfreq: exynos-bus: Replace deprecated 'devfreq' property
Date: Fri, 27 Dec 2019 09:09:58 +0900 [thread overview]
Message-ID: <a54e4275-012e-77d9-bdbe-1aab64b5c12b@samsung.com> (raw)
In-Reply-To: <20191226210119.GA8706@bogus>
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 <cw00.choi@samsung.com>
>> ---
>> .../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
next prev parent reply other threads:[~2019-12-27 0:03 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20191217055105epcas1p365e306f27fd53852b793155c929ee634@epcas1p3.samsung.com>
2019-12-17 5:57 ` [PATCH 0/9] PM / devfreq: Remove deprecated 'devfreq' and 'devfreq-events' properties Chanwoo Choi
[not found] ` <CGME20191217055105epcas1p3bacbf54550c52979fe819ab33bb21d30@epcas1p3.samsung.com>
2019-12-17 5:57 ` [PATCH 1/9] PM / devfreq: Add devfreq_get_devfreq_by_node function Chanwoo Choi
[not found] ` <CGME20191217055105epcas1p2d2930402a559e381a7854f515a683d15@epcas1p2.samsung.com>
2019-12-17 5:57 ` [PATCH 2/9] PM / devfreq: Remove devfreq_get_devfreq_by_phandle function Chanwoo Choi
2019-12-17 14:33 ` Leonard Crestez
2019-12-18 2:59 ` Chanwoo Choi
2019-12-18 3:20 ` Chanwoo Choi
[not found] ` <CGME20191217055106epcas1p3e77268d200006921dfa736b2c7550a04@epcas1p3.samsung.com>
2019-12-17 5:57 ` [PATCH 3/9] PM / devfreq: event: Add devfreq_event_get_edev_by_node function Chanwoo Choi
[not found] ` <CGME20191217055106epcas1p11f2bc81d6bb2db3fc4bc257d78c337b9@epcas1p1.samsung.com>
2019-12-17 5:57 ` [PATCH 4/9] PM / devfreq: exynos-bus: Replace deprecated 'devfreq' property Chanwoo Choi
2019-12-26 21:01 ` Rob Herring
2019-12-27 0:09 ` Chanwoo Choi [this message]
2020-01-06 1:38 ` Chanwoo Choi
2020-01-14 18:57 ` Chanwoo Choi
[not found] ` <CGME20191217055106epcas1p4b50ca647af9b54465e5c0a0bebb165b8@epcas1p4.samsung.com>
2019-12-17 5:57 ` [PATCH 5/9] PM / devfreq: exynos-bus: Replace deprecated 'devfreq-events' property Chanwoo Choi
[not found] ` <CGME20191217055106epcas1p156b1323f4ec9f7c35fed825d56e577ff@epcas1p1.samsung.com>
2019-12-17 5:57 ` [PATCH 6/9] PM / devfreq: rk3399_dmc: " Chanwoo Choi
[not found] ` <CGME20191217055106epcas1p2c43a45e34983c1b3e60cc6fd842dd33e@epcas1p2.samsung.com>
2019-12-17 5:57 ` [PATCH 7/9] memory: samsung: exynos5422-dmc: " Chanwoo Choi
2019-12-17 11:03 ` Lukasz Luba
2019-12-19 20:19 ` Krzysztof Kozlowski
[not found] ` <CGME20191217055106epcas1p4c0f65bec74e53b38d95e984e146bf8b6@epcas1p4.samsung.com>
2019-12-17 5:57 ` [PATCH 8/9] ARM: dts: exynos: Replace deprecated property for Exynos bus and DMC Chanwoo Choi
2019-12-19 20:21 ` Krzysztof Kozlowski
[not found] ` <CGME20191217055107epcas1p44d46bdea7b326b86689f326742f5444a@epcas1p4.samsung.com>
2019-12-17 5:57 ` [PATCH 9/9] arm64: dts: exynos: Replace deprecated property for Exynos bus Chanwoo Choi
2019-12-19 20:22 ` Krzysztof Kozlowski
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