Hi Rob, Gently Ping. On 12/27/19 9:09 AM, Chanwoo Choi wrote: > 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@xxxxxxxxxxx> >>> --- >>> .../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 > Are there any other commentss? -- Best Regards, Chanwoo Choi Samsung Electronics
