[PATCH 6/9] PM / OPP: dt-bindings: Add opp-interconnect-bw

On 27-09-18, 11:23, Georgi Djakov wrote:

On 08/27/2018 06:11 PM, Jordan Crouse wrote:

quoted

Add the "opp-interconnect-bw" property to specify the
average and peak bandwidth for an interconnect path for
a specific operating power point. A separate bandwidth
pair can be specified for each of the interconnects
defined for the device by appending the interconnect
name to the property.

Signed-off-by: Jordan Crouse <redacted>
---
 Documentation/devicetree/bindings/opp/opp.txt | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
index c396c4c0af92..d714c084f36d 100644
--- a/Documentation/devicetree/bindings/opp/opp.txt
+++ b/Documentation/devicetree/bindings/opp/opp.txt

@@ -170,6 +170,11 @@ Optional properties:
   functioning of the current device at the current OPP (where this property is
   present).
 
+- opp-interconnect-bw-<name>: This is an array of pairs specifying the average
+  and peak bandwidth in bytes per second for the interconnect path known by
+  'name'.  This should match the name(s) specified by interconnect-names in the
+  device definition.
+
 Example 1: Single cluster Dual-core ARM cortex A9, switch DVFS states together.
 
 / {

@@ -543,3 +548,34 @@ Example 6: opp-microvolt-<name>, opp-microamp-<name>:
 		};
 	};
 };
+
+Example 7: opp-interconnect-bw:
+(example: leaf device with frequency and BW quotas)
+
+/ {
+	soc {
+		gpu at 5000000 {
+			...
+			interconnects = <&qnoc 26 &qnoc 512>;
+			interconnect-names = "port0";
+			...
+			operating-points-v2 = <&gpu_opp_table>;
+		};
+	};
+
+	gpu_opp_table: opp_table0 {
+		compatible = "operating-points-v2";
+
+		opp-710000000 {
+			op-hz = /bits/ 64 <710000000>;
+			/* Set peak bandwidth @ 7216000 KB/s */
+			opp-interconnect-bw-port0 = /bits/ 64 <0 7216000000>;

This seems a bit long. I would suggest the following instead.
If there is only one path:
	/* average bandwidth = 0 KB/s,  peak bandwidth = 7216000 KB/s */
	opp-bw-KBps = <0 7216000>;
or 	
	opp-bw-MBps = <0 7216>;

If there are multiple paths:
	opp-bw-KBps-port0 = <0 7216000>;
	opp-bw-KBps-port1 = <0 1000000>;

The above follows a convention similar to opp-microvolt, where at
runtime the platform can pick a <name> and a matching opp-bw-KBps-<name>
property. If the platform doesn't pick a specific <name> or <name> does
not match with any of the opp-bw-KBps-<name> properties, then
opp-bw-KBps shall be used if present.
For now supporting only KBps values seems enough to cover all present
platforms, so we can start with this and based on the requirements of
future platforms we can add MBps etc.

+1

And yes I am fine with such bindings getting introduced to the OPP
core.

I am not sure if this would fit well, but have a look at
"required-opps" property in OPP bindings and see if that can be used
instead of adding new bindings here. Again, I am not sure if that
should be done :)

-- 
viresh