From mboxrd@z Thu Jan 1 00:00:00 1970 From: Georgi Djakov Subject: Re: [PATCH 1/4] dt-bindings: opp: Introduce opp-bw-MBs bindings Date: Wed, 10 Apr 2019 12:52:15 +0300 Message-ID: References: <20190313090010.20534-1-georgi.djakov@linaro.org> <20190313090010.20534-2-georgi.djakov@linaro.org> <20190314062312.vwyu3ryeyc6iv55h@vireshk-i7> <20190410040556.uwnhmhajcasic7hb@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190410040556.uwnhmhajcasic7hb@vireshk-i7> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Viresh Kumar Cc: vireshk@kernel.org, sboyd@kernel.org, nm@ti.com, robh+dt@kernel.org, mark.rutland@arm.com, rjw@rjwysocki.net, jcrouse@codeaurora.org, vincent.guittot@linaro.org, bjorn.andersson@linaro.org, amit.kucheria@linaro.org, seansw@qti.qualcomm.com, daidavid1@codeaurora.org, evgreen@chromium.org, sibis@codeaurora.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org List-Id: devicetree@vger.kernel.org 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 >>>> --- >>>> 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-: Named opp-microamp property. Similar to >>>> opp-microvolt- 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-, opp-microamp-: >>>> }; >>>> }; >>>> }; >>>> + >>>> +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- and opp-microamp-, 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 - 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