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[109.252.91.118]) by smtp.googlemail.com with ESMTPSA id h25-v6sm1285045ljh.12.2018.10.22.05.12.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Oct 2018 05:12:10 -0700 (PDT) Subject: Re: [RFC PATCH v2 01/17] OPP: Allow to request stub voltage regulators To: Viresh Kumar Cc: "Rafael J. Wysocki" , Rob Herring , Thierry Reding , Jonathan Hunter , Nishanth Menon , Stephen Boyd , Marcel Ziswiler , linux-tegra@vger.kernel.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20181021205501.23943-1-digetx@gmail.com> <20181021205501.23943-2-digetx@gmail.com> <20181022053636.ag62j3rj3vovbz53@vireshk-i7> <20181022113224.b5fiebgy2aap66nd@vireshk-i7> From: Dmitry Osipenko Message-ID: <29f893be-feed-c4c5-8468-51f7228dd468@gmail.com> Date: Mon, 22 Oct 2018 15:12:08 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20181022113224.b5fiebgy2aap66nd@vireshk-i7> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/22/18 2:32 PM, Viresh Kumar wrote: > On 22-10-18, 14:29, Dmitry Osipenko wrote: >> On 10/22/18 8:36 AM, Viresh Kumar wrote: >>> On 21-10-18, 23:54, Dmitry Osipenko wrote: >>>> Voltage regulators may be not available on some variations of HW, allow to >>>> request stub voltage regulators by OPP core in a such case to reduce code >>>> churning within drivers. >>>> >>>> Signed-off-by: Dmitry Osipenko >>>> --- >>>> drivers/cpufreq/cpufreq-dt.c | 2 +- >>>> drivers/cpufreq/ti-cpufreq.c | 3 ++- >>>> drivers/opp/core.c | 9 +++++++-- >>>> include/linux/pm_opp.h | 4 ++-- >>>> 4 files changed, 12 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c >>>> index e58bfcb1169e..6ebca472ec76 100644 >>>> --- a/drivers/cpufreq/cpufreq-dt.c >>>> +++ b/drivers/cpufreq/cpufreq-dt.c >>>> @@ -196,7 +196,7 @@ static int cpufreq_init(struct cpufreq_policy *policy) >>>> */ >>>> name = find_supply_name(cpu_dev); >>>> if (name) { >>>> - opp_table = dev_pm_opp_set_regulators(cpu_dev, &name, 1); >>>> + opp_table = dev_pm_opp_set_regulators(cpu_dev, &name, 1, false); >>>> if (IS_ERR(opp_table)) { >>>> ret = PTR_ERR(opp_table); >>>> dev_err(cpu_dev, "Failed to set regulator for cpu%d: %d\n", >>> >>> Have you actually tested this stuff ? The cpufreq-dt driver will >>> probably fail to probe if the CPU node has a "-supply" property, but >>> no regulator matching that. >>> >> >> Please notice that this patch doesn't change the original behaviour >> and I suppose that failing in a case of missing regulator is the >> expected behaviour for cpufreq-dt. Hence can't see any problem here. > > So why have this patch then ? Because there is one Tegra20 board (tegra20-trimslice) that doesn't declare necessary regulators, but we want to have CPU frequency scaling. I couldn't find board schematics and so don't know if CPU / CORE voltages are fixed on Trim-Slice or it is just preferable not to have DVFS for that board, it is an outlet-powered device [0]. Hence tegra20-cpufreq driver will request a dummy regulators when appropriate. [0] http://www.compulab.co.il/utilite-computer/web/trim-slice