[PATCH v1 0/9] Introduce Bandwidth OPPs & interconnect devfreq driver

[Saravana Kannan]

I replied[1] to this patch series[2] and described how I think interconnect
bandwidth voting should be captured in DT and how it should work.

So sending out a patch series implementing that. This patch series does the
following:
- Adds Bandwidth OPP table support (this adds device freq to bandwidth
  mapping for free)
- Adds a devfreq library for interconnect paths

Interconnects and interconnect paths quantify they performance levels in
terms of bandwidth. So similar to how we have frequency based OPP tables
in DT and in the OPP framework, this patch series adds bandwidth OPP
table support in the OPP framework and in DT.

To simplify voting for interconnects, this patch series adds helper
functions to create devfreq devices out of interconnect paths. This
allows drivers to add a single line of code to add interconnect voting
capability.

To add devfreq device for the "gpu-mem" interconnect path:
icc_create_devfreq(dev, "gpu-mem");

With the future addition of a "passive_bandwidth" devfreq governor,
device frequency to interconnect bandwidth mapping would come for free.

If the feedback on this patch series is positive, I'll then add the
devfreq passive_bandwidth governor (or something similar) to v2 of this
patch series.

So with the DT bindings added in this patch series, the DT for a GPU
that does bandwidth voting from GPU to Cache and GPU to DDR would look
something like this:

gpu_cache_opp_table: gpu_cache_opp_table {
	compatible = "operating-points-v2";

	gpu_cache_3000: opp-3000 {
		opp-peak-KBps = <3000>;
		opp-avg-KBps = <1000>;
	};
	gpu_cache_6000: opp-6000 {
		opp-peak-KBps = <6000>;
		opp-avg-KBps = <2000>;
	};
	gpu_cache_9000: opp-9000 {
		opp-peak-KBps = <9000>;
		opp-avg-KBps = <9000>;
	};
};

gpu_ddr_opp_table: gpu_ddr_opp_table {
	compatible = "operating-points-v2";

	gpu_ddr_1525: opp-1525 {
		opp-peak-KBps = <1525>;
		opp-avg-KBps = <452>;
	};
	gpu_ddr_3051: opp-3051 {
		opp-peak-KBps = <3051>;
		opp-avg-KBps = <915>;
	};
	gpu_ddr_7500: opp-7500 {
		opp-peak-KBps = <7500>;
		opp-avg-KBps = <3000>;
	};
};

gpu_opp_table: gpu_opp_table {
	compatible = "operating-points-v2";
	opp-shared;

	opp-200000000 {
		opp-hz = /bits/ 64 <200000000>;
		required-opps = <&gpu_cache_3000>, <&gpu_ddr_1525>;
	};
	opp-400000000 {
		opp-hz = /bits/ 64 <400000000>;
		required-opps = <&gpu_cache_6000>, <&gpu_ddr_3051>;
	};
};

gpu@7864000 {
	...
	operating-points-v2 = <&gpu_opp_table>, <&gpu_cache_opp_table>, <&gpu_ddr_opp_table>;
	interconnects = <&mmnoc MASTER_GPU_1 &bimc SLAVE_SYSTEL_CACHE>,
			<&mmnoc MASTER_GPU_1 &bimc SLAVE_DDR>;
	interconnect-names = "gpu-cache", "gpu-mem";
	interconnect-opp-table = <&gpu_cache_opp_table>, <&gpu_ddr_opp_table>
};

Cheers,
Saravana

[1] - https://lore.kernel.org/lkml/20190601021228.210574-1-saravanak@xxxxxxxxxx/
[2] - https://lore.kernel.org/lkml/20190423132823.7915-1-georgi.djakov@xxxxxxxxxx/ 

Saravana Kannan (9):
  dt-bindings: opp: Introduce opp-peak-KBps and opp-avg-KBps bindings
  OPP: Add support for bandwidth OPP tables
  OPP: Add helper function for bandwidth OPP tables
  OPP: Add API to find an OPP table from its DT node
  dt-bindings: interconnect: Add interconnect-opp-table property
  interconnect: Add OPP table support for interconnects
  OPP: Add function to look up required OPP's for a given OPP
  OPP: Allow copying OPPs tables between devices
  interconnect: Add devfreq support

 .../bindings/interconnect/interconnect.txt    |   8 +
 Documentation/devicetree/bindings/opp/opp.txt |  15 +-
 drivers/interconnect/Makefile                 |   2 +-
 drivers/interconnect/core.c                   |  27 +++-
 drivers/interconnect/icc-devfreq.c            | 144 ++++++++++++++++++
 drivers/opp/core.c                            | 109 +++++++++++++
 drivers/opp/of.c                              |  75 +++++++--
 drivers/opp/opp.h                             |   4 +-
 include/linux/interconnect.h                  |  17 +++
 include/linux/pm_opp.h                        |  41 +++++
 10 files changed, 426 insertions(+), 16 deletions(-)
 create mode 100644 drivers/interconnect/icc-devfreq.c

-- 
2.22.0.rc2.383.gf4fbbf30c2-goog