Hi Rob, On Mon, Jan 6, 2020 at 10:32 AM Chanwoo Choi <cw00.choi@xxxxxxxxxxx> wrote: > > Hi Rob, > > Gently Ping. Once again, ping. Could you please review? On v2[1], made separate patches for dt-binding. [1] https://patchwork.kernel.org/cover/11304545/ > > 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 -- Best Regards, Chanwoo Choi
