Hi Rob, On Tue, Apr 12, 2016 at 12:40 AM, Rob Herring <r...@kernel.org> wrote: > On Fri, Apr 08, 2016 at 01:24:51PM +0900, Chanwoo Choi wrote: >> This patch adds the documentation for generic exynos bus frequency >> driver. >> >> Signed-off-by: Chanwoo Choi <cw00.c...@samsung.com> >> Reviewed-by: Krzysztof Kozlowski <k.kozlow...@samsung.com> >> Signed-off-by: MyungJoo Ham <myungjoo....@samsung.com> >> --- >> .../devicetree/bindings/devfreq/exynos-bus.txt | 95 >> ++++++++++++++++++++++ >> 1 file changed, 95 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> >> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> new file mode 100644 >> index 000000000000..78171b918e3f >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> @@ -0,0 +1,95 @@ >> +* Generic Exynos Bus frequency device >> + >> +The Samsung Exynos SoC has many buses for data transfer between DRAM >> +and sub-blocks in SoC. Most Exynos SoCs share the common architecture >> +for buses. Generally, each bus of Exynos SoC includes a source clock >> +and a power line, which are able to change the clock frequency >> +of the bus in runtime. To monitor the usage of each bus in runtime, >> +the driver uses the PPMU (Platform Performance Monitoring Unit), which >> +is able to measure the current load of sub-blocks. >> + >> +There are a little different composition among Exynos SoC because each >> Exynos >> +SoC has different sub-blocks. Therefore, shch difference should be specified >> +in devicetree file instead of each device driver. In result, this driver >> +is able to support the bus frequency for all Exynos SoCs. > > I still have issues with this whole series. The DT hierarchy represents > buses. You are describing buses here and control of them. I would expect > to see some hierarchy, but there is none. What this looks like is you > are adding nodes based on what fits the current driver.
I already replied[1] about your same question on v2 patchset four 4 months ago. [1] https://lkml.org/lkml/2015/12/10/943 I attach the your question and my reply history as following: --------------------------------------------------------------------- [ Discussion between you and me on v2 patchset[1] ] >>> >>> This still has the same problem as before. I would expect that the bus >>> hierarchy in the dts match the hierarchy here. You just have flat nodes >>> in the example below. So all IP blocks affected by frequency scaling >>> should be under the bus node defining the OPPs. Something like this: >> >> The each bus of sub-block has not h/w dependency among sub-blocks >> and has the owned source clock / OPP table. Just they share the same >> power line. So, I think that flat nodes in the example below is not problem. > > I'm talking about the peripherals not described here. Is the ISP block > not a child of the bus_isp node? Same for the display controller block > and bus_lcd0. And so on. >From the H/W point of view, ISP block is really not included in ISP's AXI bus (bus_isp). Just, the bus_isp connect to between ISP block and DRAM. --------------------------------------------------------------------- Thanks, Chanwoo Choi
