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: Tue, 9 Apr 2019 17:39:08 +0300 Message-ID: <6d918bd9-489c-89fa-733e-90a5dabdaa0c@linaro.org> References: <20190313090010.20534-1-georgi.djakov@linaro.org> <20190313090010.20534-2-georgi.djakov@linaro.org> <20190328151255.GA5262@bogus> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190328151255.GA5262@bogus> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring Cc: vireshk@kernel.org, sboyd@kernel.org, nm@ti.com, 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 Rob, On 3/28/19 17:12, Rob Herring wrote: > On Wed, Mar 13, 2019 at 11:00:07AM +0200, 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. > > How would this work if you have 1 OPP (for the bus/interconnect/ddr) and > 2 devices with variable bandwidth needs? Or 'device' here means the > interconnect? This is a property of the consumer devices and not of the bus. It's fine for devices to have different bandwidth needs and to be connected to a shared bus. In this case the framework knows the topology and can determine which parts of the bus are shared and aggregate the traffic accordingly. >> >> 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. > > -MBps would be better IMO. Either way, units should be documented in > property-units.txt. Agree! Of course! Thanks, Georgi