Hi Viresh, On 4/10/19 07:05, Viresh Kumar wrote: > On 09-04-19, 17:36, Georgi Djakov wrote: >> Hi Viresh, >> >> On 3/14/19 08:23, Viresh Kumar wrote: >>> On 13-03-19, 11:00, Georgi Djakov wrote: >>>> 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 <[email protected]> >>>> --- >>>> 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>; >>> >>> Can we have multiple paths for a device ? >> >> I suppose that this is also a possible scenario. Will propose something >> to handle multiple paths too. >> >>>> + }; >>>> + }; >>>> + >>>> + 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>; >>> >>> In that case fixing this to just 2 entries in the array is incorrect >>> and we should take care of that in the bindings here. >> >> We can encode the path name into the property (when there are multiple >> paths). We already have opp-microamp-<name> and opp-microamp-<name>, so >> we can follow the same practice. >> >> For example: >> >> CPU0: cpu@0 { >> compatible = "arm,cortex-a53", "arm,armv8"; >> ... >> operating-points-v2 = <&cpu_opp_table>; >> /* path between the CPU and DDR and path between CPU and L3 */ >> interconnects = <&bimc MASTER_AMPSS_M0 &bimc SLAVE_EBI_CH0>, >> <&bimc MASTER_AMPSS_M0 &bimc SLAVE_L3>; >> interconnect-names "cpu-mem", "cpu-l3"; >> }; >> >> cpu_opp_table: cpu_opp_table { >> compatible = "operating-points-v2"; >> opp-shared; >> >> opp-200000000 { >> opp-hz = /bits/ 64 <200000000>; >> /* 457 MB/s average, 1525 MB/s peak bandwidth to DDR */ >> opp-bw-MBps-cpu-mem = <457 1525>; >> /* 914 MB/s average, 3050 MB/s peak bandwidth to L3 */ >> opp-bw-MBps-cpu-l3 = <914 3050>; >> }; >> }; > > The -<name> property is different as only one of the value is ever used, i.e. > we > can have opp-microvolt-speed0/1/2/3 (4 different values/properties) and only > opp-microvolt-speed1 will be used eventually and all others are discarded. > > Also I am not sure if this will be actually required. We already have a list > of > interconnects above and the order of that can be taken as reference here. i.e. > > CPU0: cpu@0 { > compatible = "arm,cortex-a53", "arm,armv8"; > ... > operating-points-v2 = <&cpu_opp_table>; > /* path between the CPU and DDR and path between CPU and L3 */ > interconnects = <&bimc MASTER_AMPSS_M0 &bimc SLAVE_EBI_CH0>, > <&bimc MASTER_AMPSS_M0 &bimc SLAVE_L3>; > }; > > cpu_opp_table: cpu_opp_table { > compatible = "operating-points-v2"; > opp-shared; > > opp-200000000 { > opp-hz = /bits/ 64 <200000000>; > /* 457 MB/s average, 1525 MB/s peak bandwidth to DDR */ > /* 914 MB/s average, 3050 MB/s peak bandwidth to L3 */ > opp-bw-MBps = <457 1525>, <914 3050>; > }; > };
This works too. > > I also strongly believe that "opp-bw-MBps" should be renamed in a way to make > it > independent of the OPPs. For example, we may have devices which also need to > add > their vote for the bandwidth but don't have an OPP table as they don't do > DVFS. > And the same property should be used by them directly as what we will have in > the individual OPPs in the above example case. > > So maybe something like bw-MBps or something else. Ok, will make it bandwidth-MBps. Thanks, Georgi
