From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rajendra Nayak Subject: Re: [RFC v2 01/11] OPP: Don't overwrite rounded clk rate Date: Mon, 17 Jun 2019 09:55:00 +0530 Message-ID: References: <20190320094918.20234-1-rnayak@codeaurora.org> <20190320094918.20234-2-rnayak@codeaurora.org> <20190611105432.x3nzqiib35t6mvyg@vireshk-i7> <20190612082506.m735bsk7bjijf2yg@vireshk-i7> <20190613095419.lfjeko7nmxtix2n4@vireshk-i7> <20190614052732.4w6vvwwich2h4cgu@vireshk-i7> <20190617035058.veo7uwqjrpa6kykt@vireshk-i7> <20190617041721.5xdr3kl4xxe6gy4m@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190617041721.5xdr3kl4xxe6gy4m@vireshk-i7> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Viresh Kumar Cc: swboyd@chromium.org, vincent.guittot@linaro.org, mturquette@baylibre.com, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org, linux-serial@vger.kernel.org, linux-spi@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-scsi@vger.kernel.org, ulf.hansson@linaro.org, dianders@chromium.org, rafael@kernel.org List-Id: linux-serial@vger.kernel.org On 6/17/2019 9:47 AM, Viresh Kumar wrote: > On 17-06-19, 09:37, Rajendra Nayak wrote: >> >> >> On 6/17/2019 9:20 AM, Viresh Kumar wrote: >>> On 14-06-19, 10:57, Viresh Kumar wrote: >>>> Hmm, so this patch won't break anything and I am inclined to apply it again :) >>>> >>>> Does anyone see any other issues with it, which I might be missing ? >>> >>> I have updated the commit log a bit more to clarify on things, please let me >>> know if it looks okay. >>> >>> opp: Don't overwrite rounded clk rate >>> The OPP table normally contains 'fmax' values corresponding to the >>> voltage or performance levels of each OPP, but we don't necessarily want >>> all the devices to run at fmax all the time. Running at fmax makes sense >>> for devices like CPU/GPU, which have a finite amount of work to do and >>> since a specific amount of energy is consumed at an OPP, its better to >>> run at the highest possible frequency for that voltage value. >>> On the other hand, we have IO devices which need to run at specific >>> frequencies only for their proper functioning, instead of maximum >>> possible frequency. >>> The OPP core currently roundup to the next possible OPP for a frequency >>> and select the fmax value. To support the IO devices by the OPP core, >>> lets do the roundup to fetch the voltage or performance state values, >>> but not use the OPP frequency value. Rather use the value returned by >>> clk_round_rate(). >>> The current user, cpufreq, of dev_pm_opp_set_rate() already does the >>> rounding to the next OPP before calling this routine and it won't >>> have any side affects because of this change. >> >> Looks good to me. Should this also be documented someplace that dev_pm_opp_set_rate() >> would not be able to distinguish between its users trying to scale CPU/GPU's vs IO >> devices, so its the callers responsibility to round it accordingly before calling the >> API? > > diff --git a/drivers/opp/core.c b/drivers/opp/core.c > index 0fbc77f05048..bae94bfa1e96 100644 > --- a/drivers/opp/core.c > +++ b/drivers/opp/core.c > @@ -751,8 +751,11 @@ static int _set_required_opps(struct device *dev, > * @dev: device for which we do this operation > * @target_freq: frequency to achieve > * > - * This configures the power-supplies and clock source to the levels specified > - * by the OPP corresponding to the target_freq. > + * This configures the power-supplies to the levels specified by the OPP > + * corresponding to the target_freq, and programs the clock to a value <= > + * target_freq, as rounded by clk_round_rate(). Device wanting to run at fmax > + * provided by the opp, should have already rounded to the target OPP's > + * frequency. > */ Perfect, thanks. -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation