linux-kernel - [PATCH v4 0/3] Introduce Bandwidth OPPs for interconnects

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Date:   Fri, 26 Jul 2019 16:15:54 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        vincent.guittot@...aro.org, seansw@....qualcomm.com,
        daidavid1@...eaurora.org, adharmap@...eaurora.org,
        Rajendra Nayak <rnayak@...eaurora.org>, sibis@...eaurora.org,
        bjorn.andersson@...aro.org, evgreen@...omium.org,
        kernel-team@...roid.com, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 0/3] Introduce Bandwidth OPPs for interconnects

Interconnects and interconnect paths quantify their performance levels in
terms of bandwidth and not in terms of frequency. So similar to how we have
frequency based OPP tables in DT and in the OPP framework, we need
bandwidth OPP table support in DT and in the OPP framework.

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 = <3000000>;
		opp-avg-KBps = <1000000>;
	};
	gpu_cache_6000: opp-6000 {
		opp-peak-KBps = <6000000>;
		opp-avg-KBps = <2000000>;
	};
	gpu_cache_9000: opp-9000 {
		opp-peak-KBps = <9000000>;
		opp-avg-KBps = <9000000>;
	};
};

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

	gpu_ddr_1525: opp-1525 {
		opp-peak-KBps = <1525000>;
		opp-avg-KBps = <452000>;
	};
	gpu_ddr_3051: opp-3051 {
		opp-peak-KBps = <3051000>;
		opp-avg-KBps = <915000>;
	};
	gpu_ddr_7500: opp-7500 {
		opp-peak-KBps = <7500000>;
		opp-avg-KBps = <3000000>;
	};
};

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

	opp-200000000 {
		opp-hz = /bits/ 64 <200000000>;
	};
	opp-400000000 {
		opp-hz = /bits/ 64 <400000000>;
	};
};

gpu@...4000 {
	...
	operating-points-v2 = <&gpu_opp_table>, <&gpu_cache_opp_table>, <&gpu_ddr_opp_table>;
	...
};

v1 -> v3:
- Lots of patch additions that were later dropped
v3 -> v4:
- Fixed typo bugs pointed out by Sibi.
- Fixed bug that incorrectly reset rate to 0 all the time
- Added units documentation
- Dropped interconnect-opp-table property and related changes

Cheers,
Saravana

Saravana Kannan (3):
  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

 Documentation/devicetree/bindings/opp/opp.txt | 15 ++++--
 .../devicetree/bindings/property-units.txt    |  4 ++
 drivers/opp/core.c                            | 51 +++++++++++++++++++
 drivers/opp/of.c                              | 41 +++++++++++----
 drivers/opp/opp.h                             |  4 +-
 include/linux/pm_opp.h                        | 19 +++++++
 6 files changed, 121 insertions(+), 13 deletions(-)

-- 
2.22.0.709.g102302147b-goog