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[94.29.35.107]) by smtp.googlemail.com with ESMTPSA id m21sm2503591lfj.47.2019.04.16.06.44.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Apr 2019 06:44:26 -0700 (PDT) Subject: Re: [PATCH v2 03/19] PM / devfreq: tegra: Don't ignore clk errors To: Chanwoo Choi , Thierry Reding , Jonathan Hunter , MyungJoo Ham , Kyungmin Park , Tomeu Vizoso Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org References: <20190415145505.18397-1-digetx@gmail.com> <20190415145505.18397-4-digetx@gmail.com> <1e4038d1-0fd3-f6d2-4e01-d34b16aeddbd@samsung.com> From: Dmitry Osipenko Message-ID: <485c7af3-453a-1c89-a677-3ef622ee2ad3@gmail.com> Date: Tue, 16 Apr 2019 16:42:47 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <1e4038d1-0fd3-f6d2-4e01-d34b16aeddbd@samsung.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 16.04.2019 4:52, Chanwoo Choi пишет: > Hi, > > On 19. 4. 15. 오후 11:54, Dmitry Osipenko wrote: >> The clk_set_min_rate() could fail and in this case clk_set_rate() sets >> rate to 0, which may drop EMC rate to minimum and make machine very >> difficult to use. >> >> Signed-off-by: Dmitry Osipenko >> --- >> drivers/devfreq/tegra-devfreq.c | 10 ++++++++-- >> 1 file changed, 8 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c >> index 0c0909fba545..69581c9082d4 100644 >> --- a/drivers/devfreq/tegra-devfreq.c >> +++ b/drivers/devfreq/tegra-devfreq.c >> @@ -487,6 +487,7 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq, >> struct tegra_devfreq *tegra = dev_get_drvdata(dev); >> struct dev_pm_opp *opp; >> unsigned long rate; >> + int err; >> >> opp = devfreq_recommended_opp(dev, freq, flags); >> if (IS_ERR(opp)) { >> @@ -496,8 +497,13 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq, >> rate = dev_pm_opp_get_freq(opp); >> dev_pm_opp_put(opp); >> >> - clk_set_min_rate(tegra->emc_clock, rate); >> - clk_set_rate(tegra->emc_clock, 0); >> + err = clk_set_min_rate(tegra->emc_clock, rate); >> + if (err) >> + return err; >> + >> + err = clk_set_rate(tegra->emc_clock, 0); >> + if (err) > > Why don't you restore the previous minimum clock for tegra->emc_clock > when failed to execute 'clk_set_rate(tegra->emc_clock, 0);'? > > I think that if you control the restoring the previous minimum clock, > it is more nice to handle the error handling. I now see that devfreq has the previous_freq field and indeed it is possible to restore the min_rate value using it. Thanks for the suggestion.