From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH v4 02/24] PM / devfreq: tegra30: Keep interrupt disabled while governor is stopped Date: Wed, 17 Jul 2019 19:44:11 +0300 Message-ID: <00dfcd92-a41a-11c0-b8b2-1cdc68048aa9@gmail.com> References: <20190707223303.6755-1-digetx@gmail.com> <20190707223303.6755-3-digetx@gmail.com> <6c517d04-cf99-f907-e74d-9fba99405a53@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Chanwoo Choi , Thierry Reding , MyungJoo Ham , Kyungmin Park , Jonathan Hunter , Tomeu Vizoso Cc: linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-tegra@vger.kernel.org 17.07.2019 9:37, Chanwoo Choi пишет: > On 19. 7. 16. 오후 10:03, Dmitry Osipenko wrote: >> 16.07.2019 14:47, Chanwoo Choi пишет: >>> On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote: >>>> There is no real need to keep interrupt always-enabled, will be nicer >>>> to keep it disabled while governor is inactive. >>>> >>>> Suggested-by: Thierry Reding >>>> Signed-off-by: Dmitry Osipenko >>>> --- >>>> drivers/devfreq/tegra30-devfreq.c | 43 ++++++++++++++++--------------- >>>> 1 file changed, 22 insertions(+), 21 deletions(-) >>>> >>>> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c >>>> index a27300f40b0b..5e2b133babdd 100644 >>>> --- a/drivers/devfreq/tegra30-devfreq.c >>>> +++ b/drivers/devfreq/tegra30-devfreq.c >>>> @@ -11,6 +11,7 @@ >>>> #include >>>> #include >>>> #include >>>> +#include >>>> #include >>>> #include >>>> #include >>>> @@ -416,8 +417,6 @@ static void tegra_actmon_start(struct tegra_devfreq *tegra) >>>> { >>>> unsigned int i; >>>> >>>> - disable_irq(tegra->irq); >>>> - >>>> actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1, >>>> ACTMON_GLB_PERIOD_CTRL); >>>> >>>> @@ -442,8 +441,6 @@ static void tegra_actmon_stop(struct tegra_devfreq *tegra) >>>> } >>>> >>>> actmon_write_barrier(tegra); >>>> - >>>> - enable_irq(tegra->irq); >>>> } >>>> >>>> static int tegra_devfreq_target(struct device *dev, unsigned long *freq, >>>> @@ -552,6 +549,12 @@ static int tegra_governor_event_handler(struct devfreq *devfreq, >>>> { >>>> struct tegra_devfreq *tegra = dev_get_drvdata(devfreq->dev.parent); >>>> >>>> + /* >>>> + * Couple device with the governor early as it is needed at >>>> + * the moment of governor's start (used by ISR). >>>> + */ >>>> + tegra->devfreq = devfreq; >>> >>> I'm not sure it is necessary. Almost devfreq device get >>> the devfreq instance on probe timing through devfreq_add_device directly. >> >> This is necessary because this assignment is for the "governor" and not >> the "device". Governor is started during of devfreq_add_device(), hence >> there is no better way to assign device to the driver's governor. > > OK. I understand. > > But, I have a question. Is it working before this patch? > How can you test it on that tegra->devfreq is NULL? It was working before this patch because previously interrupt was requested *after* devfreq_add_device(), now the IRQ requesting happens *before* devfreq_add_device() and enabling *during of*. If interrupt fires before the assignment happened, then ISR gets a NULL deference and this is easily reproducible. Please note that 'tegra->devfreq' is used only by the ISR and onward, in the further patches of this series the usage is extended by the cpufreq notifier. >> >>>> + >>>> switch (event) { >>>> case DEVFREQ_GOV_START: >>>> devfreq_monitor_start(devfreq); >>>> @@ -586,10 +589,11 @@ static struct devfreq_governor tegra_devfreq_governor = { >>>> >>>> static int tegra_devfreq_probe(struct platform_device *pdev) >>>> { >>>> - struct tegra_devfreq *tegra; >>>> struct tegra_devfreq_device *dev; >>>> - unsigned int i; >>>> + struct tegra_devfreq *tegra; >>>> + struct devfreq *devfreq; >>>> unsigned long rate; >>>> + unsigned int i; >>>> int err; >>>> >>>> tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL); >>>> @@ -625,6 +629,16 @@ static int tegra_devfreq_probe(struct platform_device *pdev) >>>> } >>>> tegra->irq = err; >>>> >>>> + irq_set_status_flags(tegra->irq, IRQ_NOAUTOEN); >>>> + >>>> + err = devm_request_threaded_irq(&pdev->dev, tegra->irq, NULL, >>>> + actmon_thread_isr, IRQF_ONESHOT, >>>> + "tegra-devfreq", tegra); >>>> + if (err) { >>>> + dev_err(&pdev->dev, "Interrupt request failed: %d\n", err); >>>> + return err; >>>> + } >>>> + >>>> reset_control_assert(tegra->reset); >>>> >>>> err = clk_prepare_enable(tegra->clock); >>>> @@ -672,28 +686,15 @@ static int tegra_devfreq_probe(struct platform_device *pdev) >>>> } >>>> >>>> tegra_devfreq_profile.initial_freq = clk_get_rate(tegra->emc_clock); >>>> - tegra->devfreq = devfreq_add_device(&pdev->dev, >>>> - &tegra_devfreq_profile, >>>> - "tegra_actmon", >>>> - NULL); >>>> + devfreq = devfreq_add_device(&pdev->dev, &tegra_devfreq_profile, >>>> + "tegra_actmon", NULL); >>>> if (IS_ERR(tegra->devfreq)) { >>> >>> Have to check 'devfreq' instead of 'tegra->devfreq'. >>> Did you test it? It might be failed because 'tegra->devfreq is NULL. >> >> That's a good catch! Thank you very much. >> >>>> err = PTR_ERR(tegra->devfreq); >>> >>> ditto. >> >> Ok