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 -- Best Regards, Chanwoo Choi Samsung Electronics
