From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH v1 3/3] i2c: tegra: Fix suspending in active runtime PM state Date: Fri, 13 Dec 2019 17:29:42 +0300 Message-ID: References: <20191212233428.14648-1-digetx@gmail.com> <20191212233428.14648-4-digetx@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20191212233428.14648-4-digetx@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Thierry Reding , Jonathan Hunter , Laxman Dewangan , Wolfram Sang Cc: linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, Mikko Perttunen List-Id: linux-tegra@vger.kernel.org 13.12.2019 02:34, Dmitry Osipenko пишет: > I noticed that sometime I2C clock is kept enabled during suspend-resume. > This happens because runtime PM defers dynamic suspension and thus it may > happen that runtime PM is in active state when system enters into suspend. > In particular I2C controller that is used for CPU's DVFS is often kept ON > during suspend because CPU's voltage scaling happens quite often. > > Note: we marked runtime PM as IRQ-safe during the driver's probe in the > "Support atomic transfers" patch, thus it's okay to enforce runtime PM > suspend/resume in the NOIRQ phase which is used for the system-level > suspend/resume of the driver. > > Signed-off-by: Dmitry Osipenko > --- > drivers/i2c/busses/i2c-tegra.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c > index b3ecdd87e91f..d309a314f4d6 100644 > --- a/drivers/i2c/busses/i2c-tegra.c > +++ b/drivers/i2c/busses/i2c-tegra.c > @@ -1790,9 +1790,14 @@ static int tegra_i2c_remove(struct platform_device *pdev) > static int __maybe_unused tegra_i2c_suspend(struct device *dev) > { > struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev); > + int err; > > i2c_mark_adapter_suspended(&i2c_dev->adapter); I'm now in a doubt that it is correct to use NOIRQ level at all for the suspend because i2c_mark_adapter_suspended() uses mutex, thus I'm wondering what will happen if there is an asynchronous transfer happening during suspend.. The i2c_mark_adapter_suspended() will try to block and will never return? > + err = pm_runtime_force_suspend(dev); > + if (err < 0) > + return err; > + > return 0; > } > > @@ -1813,6 +1818,10 @@ static int __maybe_unused tegra_i2c_resume(struct device *dev) > if (err) > return err; > > + err = pm_runtime_force_resume(dev); > + if (err < 0) > + return err; > + > i2c_mark_adapter_resumed(&i2c_dev->adapter); > > return 0; >