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[109.252.193.91]) by smtp.googlemail.com with ESMTPSA id a15sm1089438lfo.244.2021.05.17.08.23.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 May 2021 08:23:28 -0700 (PDT) Subject: Re: [PATCH v1 1/1] soc/tegra: Add devm_tegra_core_dev_init_opp_table() To: Krzysztof Kozlowski , Thierry Reding , Jonathan Hunter , Paul Fertser , Matt Merhar , Peter Geis , Nicolas Chauvet , Viresh Kumar , Stephen Boyd Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210516205138.22501-1-digetx@gmail.com> <20210516205138.22501-2-digetx@gmail.com> <3ea6b48f-af3f-51db-8d7b-1292a68ae74e@canonical.com> From: Dmitry Osipenko Message-ID: <203ffe4d-2b8e-7550-2fab-f5e3c7b5f4fe@gmail.com> Date: Mon, 17 May 2021 18:23:27 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 17.05.2021 17:52, Krzysztof Kozlowski пишет: >>>> +static int tegra_core_dev_init_opp_state(struct device *dev) >>>> +{ >>>> + struct dev_pm_opp *opp; >>>> + unsigned long rate; >>>> + struct clk *clk; >>>> + int err; >>>> + >>>> + clk = devm_clk_get(dev, NULL); >>>> + if (IS_ERR(clk)) { >>>> + dev_err(dev, "failed to get clk: %pe\n", clk); >>>> + return PTR_ERR(clk); >>>> + } >>>> + >>>> + rate = clk_get_rate(clk); >>>> + if (!rate) { >>>> + dev_err(dev, "failed to get clk rate\n"); >>>> + return -EINVAL; >>>> + } >>>> + >>>> + opp = dev_pm_opp_find_freq_ceil(dev, &rate); >>>> + >>>> + if (opp == ERR_PTR(-ERANGE)) >>>> + opp = dev_pm_opp_find_freq_floor(dev, &rate); >>>> + >>>> + err = PTR_ERR_OR_ZERO(opp); >>>> + if (err) { >>>> + dev_err(dev, "failed to get OPP for %ld Hz: %d\n", >>>> + rate, err); >>>> + return err; >>>> + } >>>> + >>>> + dev_pm_opp_put(opp); >>>> + >>>> + /* first dummy rate-setting initializes voltage vote */ >>>> + err = dev_pm_opp_set_rate(dev, rate); >>>> + if (err) { >>>> + dev_err(dev, "failed to initialize OPP clock: %d\n", err); >>>> + return err; >>>> + } >>> >>> The devm_pm_opp_set_clkname will call clk_get(), so here you should drop >>> the clk reference at the end. Why having it twice? >> The devm_pm_opp_set_clkname assigns clock to the OPP table. >> >> The devm_clk_get() is needed for the clk_get_rate(). OPP core doesn't >> initialize voltage vote and we need this initialization for the Tegra >> memory drivers. > I did not get the answer to my question. Why you need to keep the clk > reference past this point? Why you cannot drop it after getting rate? > >> The reference count of the clk will be dropped automatically once device >> driver is released. The resource-managed helper avoids the need to care >> about the error unwinding in the code, making it clean and easy to follow. > I am not saying there is a leak. > The clk reference is not needed past this point. It doesn't hurt to have additional reference since this allows to make code cleaner.