| Message ID | 20190423132823.7915-2-georgi.djakov@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/5] dt-bindings: opp: Introduce bandwidth-MBps bindings | expand |
On Wed 24 Apr 02:00 PDT 2019, Sibi Sankar wrote: > On 4/24/19 12:19 PM, Viresh Kumar wrote: > > On 24-04-19, 12:16, Rajendra Nayak wrote: > > > On 4/23/2019 6:58 PM, Georgi Djakov wrote: [..] > > > > +/ { > > > > + cpus { > > > > + CPU0: cpu@0 { > > > > + compatible = "arm,cortex-a53", "arm,armv8"; > > > > + ... > > > > + operating-points-v2 = <&cpu_opp_table>; > > > > + /* path between CPU and DDR memory and CPU and L3 */ > > > > + interconnects = <&noc MASTER_CPU &noc SLAVE_DDR>, > > > > + <&noc MASTER_CPU &noc SLAVE_L3>; > > > > + }; > > > > + }; > > > > + > > > > + cpu_opp_table: cpu_opp_table { > > > > + compatible = "operating-points-v2"; > > > > + opp-shared; > > > > + > > > > + opp-200000000 { > > > > + opp-hz = /bits/ 64 <200000000>; > > > > + /* CPU<->DDR bandwidth: 457 MB/s average, 1525 MB/s peak */ > > > > + * CPU<->L3 bandwidth: 914 MB/s average, 3050 MB/s peak */ > > > > + bandwidth-MBps = <457 1525>, <914 3050>; > > > > > > Should this also have a bandwidth-MBps-name perhaps? Without that I guess we assume > > > the order in which we specify the interconnects is the same as the order here? > > > > Right, so I suggested not to add the -name property and to rely on the > > order. Though I missed that he hasn't mentioned the order thing here. > > by skipping names, aren't we forced to specify all the specified paths > bandwidths for each opp even if it is redundant? i.e if the first/second > icc path doesn't have to change across a few opps but if the other path > does need to change this scheme would force it to be included and will > try to set the first/second path again. > > > e.g: Here the first path does not have to change across these two opps > but have to specified nonetheless since we omit names. > If this is a pair in the middle of the list, we would either have to define how non-specified values are inherited from neighbouring nodes or you will get different behavior if you're coming from a lower or a higher opp. I think it looks clearer to just be explicit and repeat the values. Regards, Bjorn > + opp-1200000000 { > + opp-hz = /bits/ 64 <1200000000>; > + bandwidth-MBps = <457 1525>, <914 3050>; > + }; > + opp-1400000000 { > + opp-hz = /bits/ 64 <1400000000>; > + bandwidth-MBps = <457 1525>, <1828 6102>; > + };
diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt index 76b6c79604a5..830f0206aea7 100644 --- a/Documentation/devicetree/bindings/opp/opp.txt +++ b/Documentation/devicetree/bindings/opp/opp.txt @@ -132,6 +132,9 @@ Optional properties: - opp-level: A value representing the performance level of the device, expressed as a 32-bit integer. +- bandwidth-MBps: The interconnect bandwidth is specified with an array containing + the two integer values for average and peak bandwidth in megabytes per second. + - clock-latency-ns: Specifies the maximum possible transition latency (in nanoseconds) for switching to this OPP from any other OPP. @@ -546,3 +549,38 @@ Example 6: opp-microvolt-<name>, opp-microamp-<name>: }; }; }; + +Example 7: bandwidth-MBps: +Average and peak bandwidth values for the interconnects between CPU and DDR +memory and also between CPU and L3 are defined per each OPP. Bandwidth of both +interconnects is scaled together with CPU frequency. + +/ { + cpus { + CPU0: cpu@0 { + compatible = "arm,cortex-a53", "arm,armv8"; + ... + operating-points-v2 = <&cpu_opp_table>; + /* path between CPU and DDR memory and CPU and L3 */ + interconnects = <&noc MASTER_CPU &noc SLAVE_DDR>, + <&noc MASTER_CPU &noc SLAVE_L3>; + }; + }; + + cpu_opp_table: cpu_opp_table { + compatible = "operating-points-v2"; + opp-shared; + + opp-200000000 { + opp-hz = /bits/ 64 <200000000>; + /* CPU<->DDR bandwidth: 457 MB/s average, 1525 MB/s peak */ + * CPU<->L3 bandwidth: 914 MB/s average, 3050 MB/s peak */ + bandwidth-MBps = <457 1525>, <914 3050>; + }; + opp-400000000 { + opp-hz = /bits/ 64 <400000000>; + /* CPU<->DDR bandwidth: 915 MB/s average, 3051 MB/s peak */ + * CPU<->L3 bandwidth: 1828 MB/s average, 6102 MB/s peak */ + bandwidth-MBps = <915 3051>, <1828 6102>; + }; + }; diff --git a/Documentation/devicetree/bindings/property-units.txt b/Documentation/devicetree/bindings/property-units.txt index bfd33734faca..9c3dbefcdae8 100644 --- a/Documentation/devicetree/bindings/property-units.txt +++ b/Documentation/devicetree/bindings/property-units.txt @@ -41,3 +41,7 @@ Temperature Pressure ---------------------------------------- -kpascal : kiloPascal + +Throughput +---------------------------------------- +-MBps : megabytes per second
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@linaro.org> --- Documentation/devicetree/bindings/opp/opp.txt | 38 +++++++++++++++++++ .../devicetree/bindings/property-units.txt | 4 ++ 2 files changed, 42 insertions(+)