linux-kernel - [PATCH 1/4] dt-bindings: opp: Introduce opp-bw-MBs bindings

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Date:   Wed, 13 Mar 2019 11:00:07 +0200
From:   Georgi Djakov <georgi.djakov@...aro.org>
To:     vireshk@...nel.org, sboyd@...nel.org, nm@...com,
        robh+dt@...nel.org, mark.rutland@....com, rjw@...ysocki.net
Cc:     jcrouse@...eaurora.org, vincent.guittot@...aro.org,
        bjorn.andersson@...aro.org, amit.kucheria@...aro.org,
        seansw@....qualcomm.com, daidavid1@...eaurora.org,
        evgreen@...omium.org, sibis@...eaurora.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        georgi.djakov@...aro.org
Subject: [PATCH 1/4] dt-bindings: opp: Introduce opp-bw-MBs bindings

In addition to frequency and voltage, some devices may have bandwidth
requirements for their interconnect throughput - for example a CPU
or GPU may also need to increase or decrease their bandwidth to DDR
memory based on the current operating performance point.

Extend the OPP tables with additional property to describe the bandwidth
needs of a device. The average and peak bandwidth values depend on the
hardware and its properties.

Signed-off-by: Georgi Djakov <georgi.djakov@...aro.org>
---
 Documentation/devicetree/bindings/opp/opp.txt | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
index 76b6c79604a5..fa598264615f 100644
--- a/Documentation/devicetree/bindings/opp/opp.txt
+++ b/Documentation/devicetree/bindings/opp/opp.txt
@@ -129,6 +129,9 @@ Optional properties:
 - opp-microamp-<name>: Named opp-microamp property. Similar to
   opp-microvolt-<name> property, but for microamp instead.
 
+- opp-bw-MBs: The interconnect bandwidth is specified with an array containing
+  the two integer values for average and peak bandwidth in megabytes per second.
+
 - opp-level: A value representing the performance level of the device,
   expressed as a 32-bit integer.
 
@@ -546,3 +549,45 @@ Example 6: opp-microvolt-<name>, opp-microamp-<name>:
 		};
 	};
 };
+
+Example 7: opp-bw-MBs:
+(example: average and peak bandwidth values are defined for each OPP and the
+interconnect between CPU and DDR memory is scaled together with CPU frequency)
+
+/ {
+	cpus {
+		CPU0: cpu@0 {
+			compatible = "arm,cortex-a53", "arm,armv8";
+			...
+			operating-points-v2 = <&cpu_opp_table>;
+			/* path between the CPU and DDR memory */
+			interconnects = <&rpm_bimc MASTER_AMPSS_M0
+					&rpm_bimc SLAVE_EBI_CH0>;
+		};
+	};
+
+	cpu_opp_table: cpu_opp_table {
+		compatible = "operating-points-v2";
+		opp-shared;
+
+		opp-200000000 {
+			opp-hz = /bits/ 64 <200000000>;
+			/* 457 MB/s average and 1525 MB/s peak bandwidth */
+			opp-bw-MBs = <457 1525>;
+		};
+		opp-400000000 {
+			opp-hz = /bits/ 64 <400000000>;
+			/* 915 MB/s average and 3051 MB/s peak bandwidth */
+			opp-bw-MBs = <915 3051>;
+		};
+		opp-800000000 {
+			opp-hz = /bits/ 64 <800000000>;
+			/* 1830 MB/s average and 6103 MB/s peak bandwidth */
+			opp-bw-MBs = <1830 6103>;
+		};
+		opp-998400000 {
+			opp-hz = /bits/ 64 <998400000>;
+			/* 2282 MB/s average and 7614 MB/s peak bandwidth */
+			opp-bw-MBs = <2284 7614>;
+		};
+	};